He thuziak hi zirchianna thupui “Advanced bioremediation technologys leh synthetic organic compounds (SOC) recycling processes” tih a ni. Article 14 awm zawng zawng en rawh
Molecular weight hniam polycyclic aromatic hydrocarbons (PAHs) naphthalene leh substituted naphthalene (methylnaphthalene, naphthoic acid, 1-naphthyl-N-methylcarbamate, etc.) te hi industry hrang hrangah hman a ni nasa hle a, thil nungte tan genotoxic, mutagenic leh/or carcinogenic an ni. Heng synthetic organic compound (SOCs) emaw xenobiotics te hi bawlhhlawh paihna atana ngaih pawimawh ber an ni a, khawvel boruak leh mipui hriselna atan hlauhawm tak an ni. Mihring thiltih chakna (eg coal gasification, oil refining, lirthei emission leh agriculture lama hmanna) hian heng hmun tina awm leh awm reng compound te concentration, fate leh transport te a hril a ni. Physical leh chemical treatment/removal method bakah hian green leh environment tichhe lo technology, bioremediation, POCs tichhe vek thei emaw, non-toxic by-product-a chantir thei microorganisms hmanga siam te chu a him, man tlawm leh beisei awm tak angin a lo chhuak ta a ni. Lei microbiota-a Proteobacteria (Pseudomonas, Pseudomonas, Comamonas, Burkholderia, leh Neosphingobacterium), Firmicutes (Bacillus leh Paenibacillus), leh Actinobacteria (Rhodococcus leh Arthrobacter) phyla-a tel bacteria chi hrang hrangte chuan organic compound hrang hrang a tichhe thei tih an lantir a ni. Metabolic study, genomics, leh metagenomic analysis te hian heng nunna chi hrang hranga awm catabolic complexity leh diversity te hi hriatthiamna min pe a, chu chu biodegradation tha tak atan hman belh theih a ni. PAHs te hi hun rei tak an awm tawh avangin plasmids, transposons, bacteriophages, genomic islands, leh integrative conjugative elements te ang chi genetic elements hmanga horizontal gene transfer hmangin novel degradation phenotypes a lo chhuak ta a ni. Systems biology leh genetic engineering of specific isolates emaw model community (consortia) te hian heng PAHs te hi synergistic effect hmangin comprehensive, rang leh efficient bioremediation a siam thei a ni. He review-ah hian metabolic pathway hrang hrang leh diversity, genetic composition leh diversity, leh naphthalene leh substituted naphthalene-degrading bacteria te cellular response/adaptations te kan ngaihtuah a ni. Hei hian field application atan ecological information a pe ang a, bioremediation tha tak neih theihna turin strain optimization a pe bawk ang.
Industry (petrochemicals, agriculture, pharmaceuticals, textile dye, cosmetics, etc.) te hmasawnna chak tak hian khawvel sum leh pai lama hmasawnna leh nunphung tihchangtlunna kawngah a pui a ni. Hetianga hmasawnna nasa tak avang hian synthetic organic compound (SOC) tam tak siam chhuah a ni a, chu chu thil chi hrang hrang siam nan hman a ni. Heng ramdang compound emaw SOCs te hi polycyclic aromatic hydrocarbons (PAHs), pesticides, herbicides, plasticizers, dyes, damdawi, organophosphates, flame retardants, volatile organic solvents, etc. te an ni a, boruakah an chhuak a, tui leh leia ecosystem-ah an chhuak a, chutah chuan multidimensional impact an nei a, detrimental effect an nei a ni physicochemical property leh community structure tihdanglamna hmanga bioform hrang hrang chungchangah (Petrie et al., 2015; Bernhardt et al., 2017; Sarkar et al., 2020). Aromatic pollutants tam tak hian intact ecosystem/biodiversity hotspot tam tak (eg coral reef, Arctic/Antarctic ice sheet, tlang sang tak tak, deep-sea sediment, etc.)-ah nghawng na tak leh tichhe thei tak a nei a (Jones 2010; Beyer et al. 2020; Nordborg et al. 2020). Tun hnaia geomicrobiological study-ah chuan synthetic organic matter (eg aromatic pollutants) leh a derivatives te chu artificial structure (built environment) (eg cultural heritage site leh monument granite, lung, thing leh metal hmanga siam) chunglama dah hian an chhe chak zawk tih an hmuchhuak (Gadd 2017; Liu et al. 2018). Mihring thiltih hian boruak bawlhhlawh leh boruak inthlak danglamna hmangin monument leh building-te biological degradation chu a tichak thei a, a tichhe thei bawk (Liu et al. 2020). Heng organic contaminants te hian boruak chhunga tui vapor nen an inrem a, structure-ah an awm a, chu chuan thil awm chu physical leh chemical degradation a thlen thin. Biodegradation hi thil nungte’n an humhalhna tichhe thei thil awm dan leh an nihna tihdanglam duh loh tak a ni tih hriat lar tak a ni (Pochon and Jaton, 1967). Heng compound te hi microbial action (metabolism) dang neih belh chuan structural integrity, conservation effectiveness leh cultural value te a tihziaawm thei a ni (Gadd, 2017; Liu et al., 2018). A lehlamah chuan, a then phei chuan heng structure te hi microbial adaptation leh response te hi a hlawkpui hle tih hmuhchhuah a ni a, biofilm leh protective crust dang siamin decay/decomposition rate a tihhniam avangin (Martino, 2016). Chuvangin, lung, thir leh thing monument-te tana hun rei tak chhunga humhalhna kawng \ha tak siam tur chuan he thil kalphung pawimawh tak takte hi uluk taka hriatthiam a ngai a ni. Natural process (geological process, forest fires, volcanic eruptions, plant leh bacterial reaction) nena khaikhin chuan mihring thiltih hian polycyclic aromatic hydrocarbons (PAHs) leh organic carbon dang (OC) tam tak ecosystem-ah a chhuah tir a ni. Agriculture-a hman PAH tam tak (insecticide leh pesticide DDT, atrazine, carbaryl, pentachlorophenol, etc.), industry (crude oil, oil sludge/waste, petroleum atanga chhuak plastic, PCB, plasticizers, detergent, disinfectant, fumigants, rimtui leh preservative), mimal enkawlna atana hman tur (sunscreen, disinfectants, insect repellent leh polycyclic musks) leh munitions (explosives 2,4,6-TNT ang chi) te hi planetary hriselna tichhe thei xenobiotics awm thei an ni (Srogi, 2007; Vamsee-Krishna and Phale, 2008; Petrie et al., 2015). He list hi petroleum atanga chhuak compound (fuel oil, lubricant, asphaltenes), high molecular weight bioplastics, leh ionic liquids te pawh huamin tihzauh theih a ni (Amde et al., 2015). Table 1-ah hian aromatic pollutant hrang hrang leh industry hrang hranga an hman dan tarlan a ni. Tun hnaiah chuan mihringte siam chhuah volatile organic compounds, chubakah carbon dioxide leh greenhouse gas dangte pawh a pung chho tan ta a ni (Dvorak et al., 2017). Mahse, anthropogenic impacts hian natural impacts aiin nasa takin a sang zawk a ni. Chu bakah, SOC engemaw zat chu environment environment tam takah an awm reng tih kan hmu a, biomes-a nghawng tha lo nei thei emerging pollutants anga hriatchhuah an ni bawk (Figure 1). Environmental agency, United States Environmental Protection Agency (USEPA) te chuan heng boruak bawlhhlawh tam tak hi an thil ngaih pawimawh ber list-ah an dah a, hei hi cytotoxic, genotoxic, mutagenic, leh carcinogenic property an neih vang a ni. Chuvangin, bawlhhlawh paih dan tur dan khauh tak leh bawlhhlawh paih dan tur ruahmanna tha tak siam a ngai a, ecosystem bawlhhlawh atanga bawlhhlawh sawngbawl/ paih chhuah a ngai a ni. Physical leh chemical hmanga enkawlna chi hrang hrang pyrolysis, oxidative thermal treatment, air aeration, landfilling, incineration, etc. te hi a hlawk lo va, a man pawh a to hle a, by-product chhe thei, toxic leh enkawl harsa tak tak a siam chhuak thin. Khawvel pum huapa boruak hriatna a pun zel avangin heng bawlhhlawh leh a atanga chhuak (halogenated, nitro, alkyl leh/ emaw methyl ang chi) tichhe thei microorganism te hian ngaihven an hlawh chho zel a (Fennell et al., 2004; Haritash and Kaushik, 2009; Phale et al., 2020; Sarkar et al., 2020 Schwanemann leh a thawhpuiten, 2020). Heng indigenous candidate microorganisms te chauh emaw, mixed culture (colonies)-a aromatic pollutants paih chhuahna atana hman hian boruak himna, senso, efficiency, effectiveness, leh sustainability lamah hlawkna a nei a ni. Researcher-te chuan microbial process te chu electrochemical redox methods, bioelectrochemical systems (BES) nena inzawmkhawm dan tur an zirchiang mek bawk a, chu chu pollutant treatment/removal atana technology beisei awm tak a ni (Huang et al., 2011). BES technology hian a efficiency sang, a man tlawm, environment safety, room temperature operation, biocompatible materials, leh by-product hlu tak tak (eg, electricity, fuel, leh chemicals) te lakchhuah theihna a neih avangin ngaihven a hlawh chho zel a ni (Pant et al., 2012; Nazari et al., 2020). High-throughput genome sequencing leh omics tools/methods lo chhuahna hian degrader microorganism hrang hrangte thiltih dan genetic regulation, proteomics, leh fluxomics chungchangah thu thar tam tak a pe a ni. Heng hmanrua te hi systems biology nena kan inzawmkhawm hian microorganisms (ie, metabolic design)-a target catabolic pathways thlan leh fine-tuning dan kan hriatthiamna a tipung zual sauh a, chu chuan biodegradation tha leh tangkai tak a siam thei a ni. Candidate microorganisms tha tak tak hmanga bioremediation strategy tha tak tak design tur chuan microorganisms te biochemical potential, metabolic diversity, genetic composition, leh ecology (autoecology/synecology) te kan hriatthiam a ngai a ni.
Fig. 1. Environment hrang hrang leh biota nghawng thei thil hrang hrang kal tlanga low-molecular PAHs lo chhuahna leh kalna. Dashed line hian ecosystem element hrang hrangte inzawmna a entir a.
He review-ah hian metabolic pathways leh diversity, degradation-a inrawlh enzymes, gene composition/content leh diversity, cellular response leh bioremediation aspect hrang hrang huamtu bacterial isolates hrang hrang hmanga simple PAHs naphthalene leh substituted naphthalenes te tihchhiat dan data te chu khaikhawm kan tum a ni. Biochemical leh molecular level hriatthiamna hian host strain tling tak tak hriatchhuahna kawngah a pui ang a, chutiang priority pollutants te bioremediation tha tak neih theihna turin an genetic engineering dang siam belh a ni ang. Hei hian bioremediation tha tak neih theihna tur site-specific bacterial consortia dinna tur strategy siamnaah a pui dawn a ni.
Toxic leh hazardous aromatic compound tam tak awmna (Huckel rule 4n + 2π electrons, n = 1, 2, 3, ... tihlawhtlingtu) hian environmental media hrang hrang boruak, leilung, sediment, leh lei chung leh leihnuai tui te tan hlauhawmna nasa tak a siam a ni (Puglisi et al., 2007). Heng compound te hian benzene ring pakhat (monocyclic) emaw benzene ring tam tak (polycyclic) emaw linear, angular emaw cluster form-a dah an nei a, negative resonance energy sang leh inertness (inertness) avang hian boruakah stability (stability/instability) an lantir a, hei hi an hydrophobicity leh reduced state atanga sawifiah theih a ni. Aromatic ring chu methyl (-CH3), carboxyl (-COOH), hydroxyl (-OH), emaw sulfonate (-HSO3) group hmanga thlak leh a nih chuan a nghet zawk a, macromolecules nen affinity chak zawk a nei a, biological system-ah pawh bioaccumulative a ni (Seo et al., 2009; Phale et al., 2020). Molecular weight hniam polycyclic aromatic hydrocarbons (LMWAH) thenkhat, naphthalene leh a derivatives [methylnaphthalene, naphthoic acid, naphthalenesulfonate, leh 1-naphthyl N-methylcarbamate (carbaryl)] te chu US Environmental Protection Agency chuan genotoxic, mutagenic, leh/ emaw carcinogenic (Cerniglia, 1984) a ni. He class of NM-PAHs hi environment-a chhuah hian food chain level zawng zawngah heng compound te hi bioaccumulation a thlen thei a, chu chuan ecosystems hriselna a nghawng thei a ni (Binkova et al., 2000; Srogi, 2007; Quinn et al., 2009).
PAHs te biota panna kawng leh an kalna kawng hi a bul berah chuan ecosystem component hrang hrang leilung, leihnuai tui, lei chung tui, thlai leh boruak te inkara inthlak danglamna leh inzawmna atanga lo chhuak a ni (Arey and Atkinson, 2003). Figure 1-ah hian ecosystem-a low molecular weight PAH hrang hrangte inzawmna leh insem darh dan leh biota/mihring exposure-a an kalna kawngte tarlan a ni. PAHs hi boruak bawlhhlawh avanga lei chung lamah leh lirthei atanga emission, industrial exhaust gas (coal gasification, combustion leh coke production) leh an deposition te migration (drift) hmanga dah a ni. Industrial lama hmalakna hrang hrang, synthetic textile, dye leh paint siam te; thing humhalh dan tur; rubber siam chhuahna; cement siamna lama hmalakna te; pesticide siamchhuahna; leh agriculture lama hmanna te hi lei leh tui chhunga PAH awmna bulpui ber a ni (Bamforth and Singleton, 2005; Wick et al., 2011). Zirna hrang hrangah chuan khawpui pawn lam leh khawpui chhunga leilung, kawngpui bul hnai, leh khawpui lianah te chuan power plant atanga emission, residential heating, air leh road traffic load, leh construction activities atanga emissions avanga polycyclic aromatic hydrocarbons (PAHs) te hi a hlauhawm zawk tih hmuhchhuah a ni (Suman et al., 2016). (2008) te chuan New Orleans, Louisiana, USA-a kawngpui bula leia PAHs chu 7189 μg/kg vel a ni tih an hmuchhuak a, open space-ah erawh chuan 2404 μg/kg chauh a ni thung. Chutiang bawkin US khawpui engemaw zatah coal gasification site bulah PAH level 300 μg/kg thleng a awm tih hmuhchhuah a ni bawk (Kanaly and Harayama, 2000; Bamforth and Singleton, 2005). India khawpui hrang hrang Delhi (Sharma et al., 2008), Agra (Dubey et al., 2014), Mumbai (Kulkarni and Venkataraman, 2000) leh Visakhapatnam (Kulkarni et al., 2014) atanga leilung ah hian PAHs a tam hle tih hmuhchhuah a ni. Aromatic compound te hi leilung chi hrang hrang, organic matter leh leilung mineral-ah awlsam zawkin an adsorb a, chu chuan ecosystem-a carbon sink lian ber a lo ni ta a ni (Srogi, 2007; Peng et al., 2008). Tui chhunga nungchate zinga PAH awm chhan lian ber chu ruahtui tlak (wet/dry precipitation leh water vapour), khawpui chhunga tui luang chhuak, bawlhhlawh paih, leihnuai tui recharge etc. te hi a ni (Srogi, 2007). Tuipui ecosystem-a PAH 80% vel chu ruahtui tlak, sedimentation, leh bawlhhlawh paih atanga lo chhuak niin an chhut (Motelay-Massei et al., 2006; Srogi, 2007). Leihnuai tuiah emaw, bawlhhlawh paihna hmun atanga tui chhuak (leachate)-a PAH awm tam zawk chu a tawpah chuan leihnuai tuiah a luang lut a, hei hian South leh Southeast Asia-a mipui 70% chuangin leihnuai tui an in avangin mipui hriselna atana hlauhawm tak a ni (Duttagupta et al., 2019). Tun hnaia zirchianna pakhat Duttagupta et al. (2020) te chuan West Bengal, India atanga lui (32) leh leihnuai tui (235) an zirchiannaah khawpui chhunga cheng 53% leh thingtlang mi 44% (a vaiin mi maktaduai 20) velin naphthalene (4.9–10.6 μg/L) leh a derivatives an tawk thei tih an hmuchhuak. Ram hman dan hrang hrang leh leihnuai tui lakchhuah tam lutuk hi lei hnuaia molecular weight hniam PAH-te vertical transport (advection) control tu ber nia ngaih a ni. Agricultural runoff, municipal leh industrial wastewater discharges, leh solid waste/barbage discharges te chu lui kam leh lei hnuai sediment-a PAHs hian a nghawng tih hmuhchhuah a ni. Atmospheric precipitation hian PAH pollution a tizual sauh sauh a ni. Khawvel puma lui/tuikhuah te, Fraser lui, Louan lui, Denso lui, Missouri lui, Anacostia lui, Ebro lui, leh Delaware luiah te PAH leh a alkyl derivatives (a vaiin 51) a tam hle tih hmuhchhuah a ni (Yunker et al., 2002; Motelay-Massei et al., 2006; Li et al., 2010 Amoako leh a thawhpuiten, 2011; Ganges lui kama sediment-ah chuan naphthalene leh phenanthrene te chu a langsar ber tih hmuhchhuah a ni (sample 70%-ah hmuhchhuah a ni) (Duttagupta et al., 2019). Chubakah, zirchianna atanga a lan dan chuan tui in tur chlorination hian toxic oxygenated leh chlorinated PAHs tam zawk a siam thei a ni (Manoli and Samara, 1999). PAHs hi lei bawlhhlawh, leihnuai tui leh ruahtui tlak atanga thlai te’n an lakluh avang hian cereal, thei leh thlaiah a pung khawm thin (Fismes et al., 2002). Tui chhunga nungcha tam tak, sangha, mussel, clams leh shrimp te hi ei leh in leh tuifinriat tui bawlhhlawh ei avang te, tissue leh vun hmang te pawhin PAHs hian an ti bawlhhlawh a ni (Mackay and Fraser, 2000). Cooking/processing methods grilling, roasting, smoking, frying, drying, baking leh charcoal cooking te pawhin ei tur ah PAHs tam tak a awm thei bawk. Hei hi meizukna tur thil thlan dan, phenolic/aromatic hydrocarbon awm zat, chaw siam dan, heater chi, tui awm zat, oxygen supply leh combustion temperature-ah a innghat nasa hle (Guillén et al., 2000; Gomes et al., 2013). Polycyclic aromatic hydrocarbons (PAHs) pawh bawnghnuteah hian a concentration hrang hrang (0.75–2.1 mg/L)-ah hmuhchhuah a ni bawk (Girelli et al., 2014). Heng PAHs te hi ei tur a an khawlkhawm dan pawh hi ei tur physicochemical property ah a innghat a, an toxic effect erawh chu physiological functions, metabolic activity, absorption, distribution leh body distribution te nen a inzawm thung (Mechini et al., 2011).
Polycyclic aromatic hydrocarbons (PAHs) te hian toxicity leh a chhiatna a thlen dan hi hun rei tak atang khan hriat a ni tawh a (Cherniglia, 1984). Molecular weight hniam polycyclic aromatic hydrocarbons (LMW-PAHs) (ring pahnih atanga pathum) te hian macromolecules hrang hrang DNA, RNA leh protein te nen covalent takin an inzawm thei a, cancer thlen thei an ni (Santarelli et al., 2008). Hydrophobic an nih avangin lipid membrane hmangin an inthen a ni. Mihringah chuan cytochrome P450 monooxygenases hian PAHs te chu epoxides ah a oxidize a, a then chu reactive sang tak (eg, baediol epoxide) an ni a, cell pangngai chu malignant ah a chantir thei bawk (Marston et al., 2001). Tin, PAHs atanga transformation products quinones, phenols, epoxides, diols, etc. te hi parent compound aiin a toxic zawk a ni. PAH thenkhat leh an metabolic intermediate te hian metabolism-a hormone leh enzyme hrang hrangte a nghawng thei a, chu chuan thanlenna, central nervous system, reproductive leh immune system te a nghawng tha lo hle a ni (Swetha and Phale, 2005; Vamsee-Krishna et al., 2006; Oostingh et al., 2008). Molecular weight hniam PAHs hun rei lote chhunga an inhriat hian asthmatics te chu lung hnathawh leh thrombosis a tichhe a, vun, lung, bladder leh gastrointestinal cancer vei theihna a tipung tih an sawi bawk (Olsson et al., 2010; Diggs et al., 2011). Ran zirchiannaah pawh PAH exposure hian reproductive function leh development-ah nghawng tha lo a nei thei a, mitdelna, kal leh thin chhiatna, leh jaundice a thlen thei tih hmuhchhuah a ni bawk. PAH biotransformation product hrang hrang diols, epoxides, quinones leh free radicals (cations) te hian DNA adduct an siam tih hmuhchhuah a ni. Stable adducts hian DNA replication machinery a tidanglam tih hmuhchhuah a ni a, unstable adducts erawh chuan DNA chu a depurinate thei thung (a bik takin adenine-ah leh a chang chuan guanine-ah) an pahnih hian tihsual an siam thei a, chu chuan mutations a thlen thei a ni (Schweigert et al. 2001). Tin, quinones (benzo-/pan-) hian reactive oxygen species (ROS) a siam thei a, DNA leh macromolecules dangte chu thihna khawpin a tichhia a, chu chuan tissue function/viability a tichhe thei bawk (Ewa and Danuta 2017). Pyrene, biphenyl leh naphthalene concentration hniam tak tak ei rei lutuk hian experimental animal-ah cancer a thlen tih an sawi (Diggs et al. 2012). Lethal toxicity an neih avangin heng PAH te hi a nghawng/contaminated site atanga tihfai/ lakchhuah hi ngaih pawimawh ber a ni.
Physical leh chemical method hrang hrang hmangin bawlhhlawh awmna hmun/environment atanga PAH te paih chhuah a ni tawh bawk. Incineration, dechlorination, UV oxidation, fixation, leh solvent extraction ang chi process te hian chhiatna tam tak a nei a, chung zingah chuan toxic by-product siam chhuah te, process complexity te, safety leh regulatory issues te, efficiency hniam te, leh man to tak te pawh a tel. Mahse, microbial biodegradation (bioremediation an tih) hi thil dang beisei awm tak a ni a, chutah chuan microorganisms te chu culture thianghlim emaw colony emaw ang chi hman a ni. Physics leh chemical method nena khaikhin chuan he process hi environment friendly, non-invasive, cost-effective, leh sustainable a ni. Bioremediation hi a nghawngna hmunah (in situ) emaw, a bik taka buatsaih hmunah (ex situ) emaw tih theih a nih avangin, hmanlai physical leh chemical method aiin remediation kalphung nghet zawka ngaih a ni (Juhasz and Naidu, 2000; Andreoni and Gianfreda, 2007; Megharaj et al., 2011; Phale et al., 2020 Sarkar leh a thawhpuiten, 2020).
Aromatic pollutants tihchhiatna atana microbial metabolic step hrang hrangte hriatthiamna hian ecological leh environmental sustainability-ah scientific leh economic lama nghawng lian tak a nei a ni. Khawvel pumah carbon (C) gram 2.1×1018 vel chu sediment leh organic compound (chu chu oil, natural gas, leh coal, chu chu fossil fuel)-ah dah a ni a, hei hian khawvel pum huapa carbon cycle-ah nasa takin a thawhhlawk hle. Mahse, industry chak tak, fossil fuel lakchhuahna, leh mihring thiltih hian heng lithospheric carbon reservoir te hi a tichhe nasa hle a, kum tin boruakah organic carbon (pollutants angin) 5.5×1015 g vel a chhuak nia chhut a ni (Gonzalez-Gaya et al., 2019). He organic carbon tam zawk hi lei leh tuipui ecosystem-ah sedimentation, transport leh runoff hmangin a lut thin. Hei bakah hian fossil fuel atanga siam synthetic pollutant thar, plastic, plasticizers leh plastic stabilizer (phthalates leh a isomers) te hian tuifinriat, leilung leh tui chhunga nungchate leh an biota te nasa takin a ti bawlhhlawh a, chu chuan khawvel boruak hlauhawmna a tizual hle a ni. Microplastic chi hrang hrang, nanoplastics, plastic fragment leh an toxic monomer products polyethylene terephthalate (PET) atanga siam te chu North America leh Southeast Asia inkar Pacific tuipuiah an pungkhawm a, “Great Pacific Garbage Patch” an siam a, tuipui nungchate a tichhe nasa hle (Newell et al., 2020). Scientific study-ah chuan chutiang boruak bawlhhlawh/bawlhhlawh chu eng physical emaw chemical emaw hmanga paih chhuah theih a ni lo tih a chiang hle. Hemi kawngah hian microorganism tangkai ber chu pollutants te chu carbon dioxide, chemical energy leh non-toxic by-product dang ah oxidatively metabolize thei te an ni a, a tawpah chuan nutrient cycling process dang (H, O, N, S, P, Fe, etc.) ah an lut ta a ni. Chutiang chuan, aromatic pollutant mineralization microbial ecophysiology hriatthiamna leh a environment control hriatthiam hi microbial carbon cycle, net carbon budget leh nakin lawka climate risk te tehna atan a pawimawh hle. Chutiang compound chu boruak atanga paih chhuah vat a tulzia ngaihtuah chuan technology thianghlim lam hawia eco-industry hrang hrang a lo chhuak ta a ni. A dang pawhin, ecosystem-a industrial waste/waste chemicals khawlkhawmte valueization (ie waste to wealth approach) chu circular economy leh sustainable development goal-a lungphum pakhatah ngaih a ni (Close et al., 2012). Chuvangin, heng degradation candidate awm thei te metabolic, enzymatic leh genetic aspect hriatthiam hi chutiang aromatic pollutants te tha taka paih leh bioremediation atan chuan a pawimawh ber a ni.
Aromatic pollutants tam tak zingah hian low-molecular-weight PAHs naphthalene leh substituted naphthalenes te hi kan ngaihven hle a ni. Heng compound te hi petroleum atanga siam fuel, textile dye, consumer products, pesticides (mothballs leh insect repellent), plasticizers leh tannins te siamtu lian ber an ni a, chuvangin ecosystem tam takah an hluar hle a ni (Preuss et al., 2003). Tun hnaia report-te chuan aquifer sediment, leihnuai tui leh lei hnuai leilung, vadose zone leh lui kamah naphthalene concentration a pungkhawm dan a tarlang a, hei hian environment-a a bioaccumulation a tilang a ni (Duttagupta et al., 2019, 2020). Table 2-ah hian naphthalene leh a derivatives te physicochemical property, application leh health effect te tarlan a ni. High-molecular-weight PAH dang nena khaikhin chuan naphthalene leh a derivatives te hi hydrophobic an ni lo va, tuiah an inthiar tam zawk a, ecosystem-ah pawh an darh zau hle a, chuvangin PAHs te metabolism, genetics leh metabolic diversity zir chianna atan model substrate atan an hmang fo thin. Microorganism tam tak chuan naphthalene leh a derivatives te chu an metabolize thei a, an metabolic pathways, enzymes leh regulatory features te chungchangah information kimchang tak a awm bawk (Mallick et al., 2011; Phale et al., 2019, 2020). Hei bakah hian naphthalene leh a derivatives te hi an tamna leh bioavailability a san avangin environment pollution assessment atan prototype compound atan ruat an ni bawk. US Environmental Protection Agency chuan cigarette meikhu atanga cubic meter khatah naphthalene level average chu 5.19 μg a ni a, a bik takin kang kim lo atanga 5.19 μg a ni a, sidestream meikhu atanga 7.8 atanga 46 μg a ni a, creosote leh naphthalene laka invenna erawh a let 100 atanga 10,000 velin a sang zawk niin an chhut (Preuss et al. 2003 a ni). A bik takin Naphthalene hian species-, region-, leh sex-specific respiratory toxicity leh carcinogenicity a nei tih hmuhchhuah a ni. Rannung zirchianna atanga a lan dan chuan International Agency for Research on Cancer (IARC) chuan naphthalene chu “mihring cancer thlen thei” (Group 2B)1. Substituted naphthalenes nena inzawmna, a bik takin inhalation emaw parenteral (oral) administration hmanga pek hian lung tissue a ti na a, rat leh mice-ah lung tumor a tipung bawk (National Toxicology Program 2). Acute effects chu luak chhuak, luak chhuak, pum na, luak chhuak, lu na, buai, thawk hah lutuk, khawsik, tachycardia, etc. A lehlamah chuan broad-spectrum carbamate insecticide carbaryl (1-naphthyl N-methylcarbamate) hi tui chhunga invertebrates, amphibians, honey bees leh mihringah a awm a, acetylcholinesterase a titawp a, paralysis a thlen thei tih hmuhchhuah a ni bawk (Smulders et al., 2003; Bulen and Distel, 2011). Chuvangin, microbial degradation, genetic regulation, enzymatic leh cellular reaction te mechanism hriatthiam hi boruak bawlhhlawh tak takah bioremediation strategy siamna atan a pawimawh hle.
Table 2. Naphthalene leh a derivatives te physicochemical property, hman dan, hriat theih dan leh a kaihhnawih natna chungchang chipchiar taka tarlanna.
Polluted niche-ah chuan hydrophobic leh lipophilic aromatic pollutants hian environment microbiome (community)-ah cellular effect hrang hrang a thlen thei a, chu chu membrane fluidity inthlak danglamna, membrane permeability, lipid bilayer swelling, energy transfer tihbuai (electron transport chain/proton motive force), leh membrane-associated proteins activity (Sikkema et al.,,) te hi a ni. 1995-ah a ziak a). Chu bakah, soluble intermediate thenkhat catechol leh quinones te hian reactive oxygen species (ROS) an siam a, DNA leh protein te nen adduct an siam bawk (Penning et al., 1999). Chutiang chuan ecosystem-a hetiang compound tam lutuk hian microbial community-te chu physiological level hrang hranga degrader tha tak ni turin selective pressure a pe a, chung zingah chuan uptake/transport, intracellular transformation, assimilation/utilization, leh compartmentalization te pawh a tel a ni.
Ribosomal Database Project-II (RDP-II) an zirchiannaah chuan naphthalene emaw a derivatives emaw hmanga tihbawlhhlawh media emaw enrichment culture atanga bacteria chi hrang hrang 926 lakchhuah a ni tih hmuhchhuah a ni. Proteobacteria group-ah hian aiawh tam ber (n = 755) an awm a, an dawttu chu Firmicutes (52), Bacteroidetes (43), Actinobacteria (39), Tenericutes (10), leh unclassified bacteria (8) te an ni (Figure 2). γ-Proteobacteria (Pseudomonadales leh Xanthomonadales) aiawh te hian Gram-negative group zawng zawngah G+C tamna (54%) an thunun a, Clostridiales leh Bacillales (30%) te chu Gram-positive group G+C hniam tak tak an ni thung. Pseudomonas (a tam ber, chi 338) hian naphthalene leh a methyl derivatives te chu ecosystem bawlhhlawh hrang hrang (coal tar, petroleum, crude oil, sludge, oil spills, wastewater, organic waste leh landfills) bakah intact ecosystem (lei, lui, sediment leh leihnuai tui) ah te a tichhe thei niin an sawi bawk. (Figure 2-ah hian a awm). Chubakah, heng hmun thenkhata enrichment study leh metagenomic analysis-ah hian uncultured Legionella leh Clostridium species te hian degradative capacity an nei thei tih hmuhchhuah a ni a, hei hian kawng thar leh metabolic diversity zirchian nan heng bacteria te hi culture a ngai tih a tilang bawk.
Fig. 2. Naphthalene leh naphthalene derivatives hmanga bawlhhlawh awmna hmuna bacteria aiawhtute taxonomic diversity leh ecological distribution.
Aromatic hydrocarbon tichhe thei microorganism hrang hrang zingah hian a tam zawk chu carbon leh energy pe chhuaktu awmchhun atan naphthalene tichhe thei an ni. Naphthalene metabolism-a thil thleng hrang hrangte chu Pseudomonas sp. (strain: NCIB 9816-4, G7, AK-5, PMD-1 leh CSV86), Pseudomonas stutzeri AN10, Pseudomonas fluorescens PC20 leh chi dang (ND6 leh AS1) (Mahajan leh a thawhpui, 1994; Resnick leh a thawhpui, 1996; Annweiler leh a thawhpui, 2000; Basu leh a thawhpuiten, 2003;Dennis leh Zylstra, 2004;Sota leh a thawhpuiten, 2006; naphthalene chu cis-naphthalenediol ah a chang (Figure 3) Cis-dihydrodiol chu dehydrogenase hmangin 1,2-dihydroxynaphthalene ah a chantir a 2-hydroxychromene-2-carboxylic acid Enzymatic cis-trans isomerization hian trans-o-hydroxybenzylidenepyruvate a siam a, chu chu hydratase aldolase hmangin salicylic aldehyde leh pyruvate-ah a inthen darh a ni. NAD+-a innghat salicylaldehyde dehydrogenase hian salicylaldehyde chu salicylic acid-ah a chantir a, he kawng hi naphthalene tihchhiatna “upper pathway” an ti a, mahse, a danglamna tlemte a awm a, entirnan, thermophilic Bacillus hamburgii 2, naphthalene degradation-ah chu naphthalene 2,3-dioxygenase hmangin a intan a, 2,3-dihydroxynaphthalene a siam a ni (Annweiler et al., 2000).
Figure 3. Naphthalene, methylnaphthalene, naphthoic acid leh carbaryl te tihchhiatna kawng. Circled number hian naphthalene leh a derivatives te chu a hnu lama thil siamah a inthlak danglam zelna tura mawhphurtu enzyme te a entir a ni. 1 — naphthalene dioxygenase (NDO) hmanga siam a ni a; 2, cis-dihydrodiol dehydrogenase hmanga siam a ni a; 3, 1,2-dihydroxynaphthalene dioxygenase hmanga siam a ni a; 4, 2-hydroxychromene-2-carboxylic acid isomerase hmanga siam a ni a; 5, trans-O-hydroxybenzylidenepyruvate hydratase aldolase hmanga siam a ni a; 6, salicylaldehyde dehydrogenase hmanga siam a ni a; 7, salicylate 1-hydroxylase hmanga siam a ni a; 8, catechol 2,3-dioxygenase (C23DO) te chu a awm a; 9, 2-hydroxymuconate semialdehyde dehydrogenase hmanga siam a ni a; 10, 2-oxopent-4-enoate hydratase hmanga siam a ni a; 11, 4-hydroxy-2-oxopentanoate aldolase hmanga siam a ni a; 12, acetaldehyde dehydrogenase hmanga siam a ni a; 13, catechol-1,2-dioxygenase (C12DO) te chu a awm a; 14, muconate cycloisomerase hmanga siam a ni a; 15, muconolactone delta-isomerase hmanga siam a ni a; 16, β-ketoadipatenollactone hydrolase hmanga siam a ni a; 17, β-ketoadipate succinyl-CoA transferase hmanga siam a ni a; 18, β-ketoadipate-CoA thiolase hmanga siam a ni a; 19, succinyl-CoA: acetyl-CoA succinyltransferase, a chhuahna tur hmun leh a hmanna tur hmun; 20, salicylate 5-hydroxylase hmanga siam a ni a; 21 – gentisate 1,2-dioxygenase (GDO) hmanga siam a ni a; 22, maleylpyruvate isomerase hmanga siam a ni a; 23, fumarylpyruvate hydrolase hmanga siam a ni a; 24, methylnaphthalene hydroxylase (NDO) hmanga siam a ni a; 25, hydroxymethylnaphthalene dehydrogenase hmanga siam a ni a; 26, naphthaldehyde dehydrogenase hmanga siam a ni a; 27, 3-formylsalicylic acid oxidase hmanga siam a ni a; 28, hydroxyisophthalate decarboxylase hmanga siam a ni a; 29, carbaryl hydrolase (CH) te chu a awm a; 30, 1-naphthol-2-hydroxylase hmanga siam a ni.
Organism leh a genetic makeup a zirin a lo chhuak salicylic acid chu salicylate 1-hydroxylase (S1H) hmanga catechol pathway kaltlangin emaw, salicylate 5-hydroxylase (S5H) hmanga gentisate pathway kaltlangin emaw a metabolize lehzual a ni (Figure 3). Naphthalene metabolism (upper pathway)-a salicylic acid hi intermediate lian ber a nih avangin salicylic acid atanga TCA intermediate thlenga step te hi lower pathway tia sawi a ni fo a, genes te chu operon pakhatah an insiam a ni. Upper pathway operon (nah) leh lower pathway operon (sal)-a gene awmte hi common regulatory factors-in a thunun tih hmuh tur a awm a entirnan, NahR leh salicylic acid te hian inducer angin hna an thawk a, operon pahnih te hian naphthalene chu an metabolize vek thei a ni (Phale et al., 2019, 2020).
Chu bakah, catechol chu catechol 2,3-dioxygenase (C23DO) (Yen et al., 1988) hmangin meta pathway hmangin 2-hydroxymuconate semialdehyde-ah cyclically cleaved a ni a, 2-hydroxymuconate semialdehyde hydrolase hmangin hydrolyze lehin 2-hydroxypent-2,4-dienoic acid a siam bawk. Chumi hnuah 2-hydroxypent-2,4-dienoate chu hydratase (2-oxopent-4-enoate hydratase) leh aldolase (4-hydroxy-2-oxopentanoate aldolase) hmangin pyruvate leh acetaldehyde-ah a chantir a, chutah chuan central carbon pathway-ah a lut leh a (Figure 3). A dang pawhin catechol chu catechol 1,2-oxygenase (C12DO) hmangin ortho pathway hmangin cis,cis-muconate-ah cyclically cleaved a ni bawk. Muconate cycloisomerase, muconolactone isomerase, leh β-ketoadipate-nollactone hydrolase te hian cis,cis-muconate chu 3-oxoadipate ah an chantir a, chu chu succinyl-CoA leh acetyl-CoA kaltlangin central carbon pathway ah a lut a (Nozaki et al., 1968) (Figure 3).
Gentisate (2,5-dihydroxybenzoate) pathway-ah chuan aromatic ring chu gentisate 1,2-dioxygenase (GDO) hmangin a cleave a, maleylpyruvate a siam a ni. He thil hi direct-a hydrolyze-in pyruvate leh malate-ah siam theih a ni a, a nih loh leh isomerized-in fumarylpyruvate siam theih a ni a, chu chu hydrolyze-in pyruvate leh fumarate-ah a chang thei bawk (Larkin and Day, 1986). Alternative pathway thlan hi Gram-negative leh Gram-positive bacteria-ah te biochemical leh genetic level-ah hmuh a ni tawh (Morawski et al., 1997; Whyte et al., 1997). Gram-negative bacteria (Pseudomonas) te chuan salicylic acid an hmang duh zawk a, hei hi naphthalene metabolism tichhuaktu a ni a, salicylate 1-hydroxylase hmangin catechol ah a decarboxylating a ni (Gibson and Subramanian, 1984). A lehlamah chuan Gram-positive bacteria (Rhodococcus)-ah chuan salicylate 5-hydroxylase hian salicylic acid chu gentisic acid-ah a chantir a, salicylic acid erawh chuan naphthalene genes transcription-ah inductive effect a nei lo thung (Grund et al., 1992) (Figure 3).
Pseudomonas CSV86, Oceanobacterium NCE312, Marinhomonas naphthotrophicus, Sphingomonas paucimobilis 2322, Vibrio cyclotrophus, Pseudomonas fluorescens LP6a, Pseudomonas leh Mycobacterium chi hrang hrangte hian monomethylnaphthalene emaw dimethylnaphthalene (Dean-Raymond leh Bartha, 1975; Cane leh Williams, 1982; Mahajan leh a thawhpui, 1994; Dutta leh a thawhpui, 1998; Hedlund leh a thawhpui, 1999). Chung zingah chuan Pseudomonas sp. CSV86 hi biochemical leh enzymatic level-ah chiang takin zirchian a ni tawh a (Mahajan et al., 1994). 1-Methylnaphthalene hi kawng hnih hmangin a inthlak danglam thin. A hmasain aromatic ring chu hydroxylated (methylnaphthalene unsubstituted ring) a ni a, cis-1,2-dihydroxy-1,2-dihydro-8-methylnaphthalene a siam a, chu chu oxidized lehin methyl salicylate leh methylcatechol-ah a chang a, chutah chuan ring cleavage hnuah central carbon pathway-ah a lut leh a (Figure 3). He kawng hi “carbon source pathway” an ti a. “Detoxification pathway” pahnihnaah chuan methyl group chu NDO hmangin hydroxylate-in 1-hydroxymethylnaphthalene a siam thei a, chu chu 1-naphthoic acid-ah oxidized lehin culture medium-ah dead-end product angin a paih chhuak leh a ni. Zirna hrang hrangah chuan strain CSV86 hian carbon leh energy source awmchhun atan 1- leh 2-naphthoic acid-ah a thang thei lo tih hmuhchhuah a ni a, hei hian a detoxification pathway a nemnghet a ni (Mahajan et al., 1994; Basu et al., 2003). 2-methylnaphthalene ah chuan methyl group chu hydroxylase hmangin hydroxylation a nei a, 2-hydroxymethylnaphthalene a siam a ni. Chu bakah, naphthalene ring-a unsubstituted ring chuan ring hydroxylation hmangin dihydrodiol a siam a, chu chu enzyme-catalyzed reaction hrang hrangah 4-hydroxymethylcatechol-ah oxidized a ni a, meta-ring cleavage pathway hmangin central carbon pathway-ah a lut a ni. Chutiang bawkin S. paucimobilis 2322 hian NDO hmangin 2-methylnaphthalene chu hydroxylate turin a hmang tih an sawi a, chu chu oxidized lehin methyl salicylate leh methylcatechol a siam niin an sawi bawk (Dutta et al., 1998).
Naphthoic acids (substituted/unsubstituted) hi methylnaphthalene, phenanthrene leh anthracene te tihchhiat avanga detoxification/biotransformation by-product lo awm, hman tawh culture medium-a chhuah a ni. Leia isolate Stenotrophomonas maltophilia CSV89 hian 1-naphthoic acid chu carbon source atan a metabolize thei tih an sawi (Phale et al., 1995). Metabolism hi aromatic ring dihydroxylation atanga tan niin 1,2-dihydroxy-8-carboxynaphthalene siam a ni. Diol lo chhuak chu 2-hydroxy-3-carboxybenzylidenepyruvate, 3-formylsalicylic acid, 2-hydroxyisophthalic acid leh salicylic acid hmangin catechol-ah oxidized a ni a, meta-ring cleavage pathway hmangin central carbon pathway-ah a lut a ni (Figure 3).
Carbaryl hi naphthyl carbamate pesticide a ni a. Kum 1970 chhoa India rama Green Revolution a lo thlen atang khan chemical fertilizer leh pesticide hman a nih avangin agricultural non-point source atanga polycyclic aromatic hydrocarbon (PAH) emission a tipung a (Pingali, 2012; Duttagupta et al., 2020). India rama thlai chinna ram zawng zawng 55% (hectare 85,722,000) vel chu chemical pesticide hmanga tihthianghlim a ni nia chhut a ni. Kum nga kalta (2015–2020) chhung khan India rama agriculture sector-ah kum tin a vaiin pesticide ton 55,000 atanga 60,000 vel hman a ni (Department of Cooperatives and Farmers Welfare, Ministry of Agriculture, Government of India, August 2020). Gangetic tlangram hmar leh khawthlang lam (mipui leh mihring tamna ber state)-ah chuan thlai chi hrang hrangah pesticide hman a hluar hle a, insecticides hman a ni nasa hle. Carbaryl (1-naphthyl-N-methylcarbamate) hi broad-spectrum, moderately to highly toxic carbamate insecticide a ni a, India ram agriculture-ah hman a ni a, a vaiin ton 100–110 vel a ni. Trade name Sevin hmanga hralh a ni tlangpui a, thlai chi hrang hrang (maize, soybean, cotton, thei leh thlai) tichhe thei rulhut (aphids, fire ants, fleas, mites, spiders leh pawn lama rannung dang tam tak) te dona atan hman a ni. Microorganism thenkhat chu Pseudomonas (NCIB 12042, 12043, C4, C5, C6, C7, Pseudomonas putida XWY-1), Rhodococcus (NCIB 12038), Sphingobacterium spp. (CF06), Burkholderia (C3), Micrococcus leh Arthrobacter te hi rannung dang tihreh nan hman theih a ni bawk. RC100 hian carbaryl a tichhe thei tih an sawi (Larkin leh Day, 1986; Chapalamadugu leh Chaudhry, 1991; Hayatsu leh a thawhpui te, 1999; Swetha leh Phale, 2005; Trivedi leh a thawhpui te, 2017). Carbaryl chhiatna kawng hi biochemical, enzymatic leh genetic level-ah nasa takin zirchian a ni tawh a, Pseudomonas sp. Strain C4, C5 leh C6 (Swetha leh Phale, 2005; Trivedi leh a thawhpuiten, 2016) (Fig. 3). Metabolic pathway hi carbaryl hydrolase (CH) hmanga ester bond hydrolysis atanga tan niin 1-naphthol, methylamine leh carbon dioxide te a siam a ni. Chumi hnuah 1-naphthol chu 1-naphthol hydroxylase (1-NH) hmangin 1,2-dihydroxynaphthalene-ah a chantir a, chu chu central carbon pathway hmangin salicylate leh gentisate hmangin a metabolize lehzual a ni. Carbaryl tichhe thei bacteria thenkhat chuan catechol ortho ring cleavage hmangin salicylic acid ah an metabolize tih an sawi (Larkin and Day, 1986; Chapalamadugu and Chaudhry, 1991). Hriat tur pawimawh tak chu naphthalene tichhe thei bacteria te hian catechol hmangin salicylic acid an metabolize ber a, carbaryl tichhe thei bacteria erawh chuan gentisate pathway hmangin salicylic acid an metabolize duh zawk thung.
Naphthalenesulfonic acid/disulfonic acid leh naphthylaminesulfonic acid derivatives te hi azo dye, wetting agents, dispersants, etc. siamnaah intermediate atan hman theih a ni a, heng compound te hian mihring tan toxicity nei tlem mahse, cytotoxicity assessment-ah chuan sangha, daphnia leh algae te tan chuan thihna thlen thei an ni tih hmuhchhuah a ni (Greim et al., 1994). Pseudomonas chi (strains A3, C22) aiawh te hian sulfonic acid group awmna aromatic ring chu double hydroxylation hmangin metabolism an tan tir a, dihydrodiol an siam a, chu chu sulfite group chu spontaneous cleavage hmangin 1,2-dihydroxynaphthalene ah a inthlak leh thin tih an sawi (Brilon et al., 1981). Chuta chhuak 1,2-dihydroxynaphthalene chu classical naphthalene pathway, chu chu catechol emaw gentisate pathway hmangin catabolized a ni (Figure 4). Aminophthalenesulfonic acid leh hydroxynaphthalenesulfonic acid te hi mixed bacterial consortia hmangin complementary catabolic pathways neiin a chhe vek thei tih hmuhchhuah a ni (Nortemann et al., 1986). Consortium member pakhat chuan aminonaphthalenesulfonic acid emaw hydroxynaphthalenesulfonic acid emaw chu 1,2-dioxygenation hmangin a desulfurized tih hmuhchhuah a ni a, aminosalicylate emaw hydroxysalicylate emaw chu culture medium-ah dead-end metabolite angin a chhuak a, chumi hnuah consortium member dangte chuan an la lut ta a ni. Naphthalenedisulfonic acid hi polar deuh mahse biodegradable tha lo tak a nih avangin kawng hrang hrang hmangin a metabolize thei a ni. Desulfurization hmasa ber chu aromatic ring leh sulfonic acid group regioselective dihydroxylation laiin a thleng a; desulfurization pahnihna chu salicylic acid 5-hydroxylase hmanga 5-sulfosalicylic acid hydroxylation-in gentisic acid siam a nih laiin a thleng a, chu chu central carbon pathway-ah a lut a ni (Brilon et al., 1981) (Figure 4). Naphthalene tihchhiatna atana mawhphurtu enzyme te hian naphthalene sulfonate metabolism siamtu an ni bawk (Brilon et al., 1981; Keck et al., 2006).
Figure 4. Naphthalene sulfonate tihchhiatna atana metabolic pathways. Circle chhunga number awmte hian naphthyl sulfonate metabolism mawhphurtu enzyme te a entir a, FIG. 3. A rilru a hah lutuk chuan a rilru a buai em em a.
Low molecular weight PAHs (LMW-PAHs) hi tihtlem theih, hydrophobic leh poorly soluble an ni a, chuvangin natural breakdown/degradation-ah an hlauhawm lo. Mahse, aerobic microorganisms te hian molecular oxygen (O2) an hip lut a, an oxidize thei a ni. Heng enzyme te hi oxidoreductases class ah an tel ber a, reaction hrang hrang aromatic ring hydroxylation (mono- or dihydroxylation), dehydrogenation leh aromatic ring cleavage te an ti thei a ni. Heng reaction atanga thil hmuhchhuah te hi oxidation state sang zawkah an awm a, central carbon pathway hmangin awlsam zawkin an metabolize thei a ni (Phale et al., 2020). Degradation pathway-a enzyme awmte hi inducible an nih thu an sawi. Cell te hi carbon source awlsam tak, glucose emaw organic acid emaw hmanga tihpun a nih chuan heng enzyme te hnathawh hi a hniam hle emaw, a tlem hle emaw a ni. Table 3-ah hian naphthalene leh a derivatives metabolism-a inrawlh enzyme hrang hrang (oxygenases, hydrolases, dehydrogenases, oxidases, etc.) te chu a kimchangin tarlan a ni.
Table 3. Naphthalene leh a derivatives tihchhiatna atana mawhphurtu enzyme te biochemical characteristic.
Radioisotope study (18O2) chuan oxygenases te hian aromatic ring-a molecular O2 an dah luh hi compound pakhat biodegradation dang activate nana step pawimawh ber a ni tih hmuhchhuah a ni (Hayaishi et al., 1955; Mason et al., 1955). Molecular oxygen (O2) atanga oxygen atom pakhat (O) chu substrate-a dah luh hi endogenous emaw exogenous monooxygenases (hydroxylases an ti bawk) emaw hmangin a intan a ni. Oxygen atom dang chu tuiah a tlahniam ta a ni. Exogenous monooxygenases hian NADH emaw NADPH emaw hmangin flavin a tihtlem a, endomonooxygenases ah erawh chuan substrate hian flavin a tihtlem thung. Hydroxylation awmna hian product siamnaah chi hrang hrang a siam a ni. Entirnan, salicylate 1-hydroxylase hian C1 position-ah salicylic acid chu a hydroxylate a, catechol a siam a ni. A lehlamah chuan multicomponent salicylate 5-hydroxylase (reductase, ferredoxin, leh oxygenase subunits awmna) hian C5 position-ah salicylic acid chu hydroxylate-in gentisic acid a siam a ni (Yamamoto et al., 1965).
Dioxygenases hian substrate chhungah O2 atom pahnih a dah lut a. Product siam dan azirin ring hydroxylating dioxygenases leh ring cleaving dioxygenases ah te an inthen a. Ring hydroxylating dioxygenases hian aromatic substrate te chu cis-dihydrodiols (eg, naphthalene) ah a chantir a, bacteria zingah a darh zau hle. Tun thleng hian ring hydroxylating dioxygenases nei organism te hi aromatic carbon source hrang hrangah an thang lian thei tih hmuhchhuah a ni a, heng enzyme te hi NDO (naphthalene), toluene dioxygenase (TDO, toluene), leh biphenyl dioxygenase (BPDO, biphenyl) tiin an thliar hrang a ni. NDO leh BPDO te hian polycyclic aromatic hydrocarbon hrang hrang (toluene, nitrotoluene, xylene, ethylbenzene, naphthalene, biphenyl, fluorene, indole, methylnaphthalene, naphthalenesulfonate, phenanthrene, anthracene, acetophenone, etc.) te double oxidation leh side chain hydroxylation an tichak thei a ni. (Boyd leh Sheldrake, 1998; Phale leh a thawhpuiten, 2020). NDO hi multicomponent system a ni a, oxidoreductase, ferredoxin leh active site-containing oxygenase component te a awm a (Gibson and Subramanian, 1984; Resnick et al., 1996). NDO catalytic unit hi α subunit lian tak leh β subunit te tak te α3β3 configuration-a inrem a ni. NDO hi oxygenases chhungkaw lian takah a tel a, a α-subunit hian Rieske site [2Fe-2S] leh mononuclear non-heme iron a nei a, hei hian NDO substrate specificity a tichiang a ni (Parales et al., 1998). A tlangpuiin catalytic cycle khatah pyridine nucleotide reduction atanga electron pahnih chu reductase, ferredoxin leh Rieske site hmangin active site-a Fe(II) ion-ah an transfer thin. Reducing equivalents hian molecular oxygen a tichak a, hei hi substrate dihydroxylation atana thil tul hmasa ber a ni (Ferraro et al., 2005). Tun thleng hian NDO tlemte chauh hi strain hrang hrang atanga tihthianghlim leh chipchiar taka characterized a ni tawh a, naphthalene tihchhiatna kawng hrang hrangte genetic control pawh chipchiar takin zirchian a ni tawh bawk (Resnick et al., 1996; Parales et al., 1998; Karlsson et al., 2003). Ring-cleaving dioxygenases (endo- emaw ortho-ring-cleaving enzymes leh exodiol- emaw meta-ring-cleaving enzymes) te hian hydroxylated aromatic compounds ah hna an thawk a. Entirnan, ortho-ring-cleaving dioxygenase chu catechol-1,2-dioxygenase a ni a, meta-ring-cleaving dioxygenase erawh chu catechol-2,3-dioxygenase a ni thung (Kojima et al., 1961; Nozaki et al., 1968). Oxygenase hrang hrang bakah hian aromatic dihydrodiols, alcohols leh aldehydes te dehydrogenation siamtu leh NAD+/NADP+ chu electron acceptor atana hmangtu dehydrogenases hrang hrang a awm bawk a, chungte chu metabolism-a inrawlh enzyme pawimawh thenkhat an ni (Gibson and Subramanian, 1984; Shaw and Harayama, 1990; Fahle et al., 2020).
Hydrolases (esterases, amidases) ang chi enzyme te hi enzyme class pawimawh pahnihna an ni a, tui hmangin covalent bonds an cleave a, broad substrate specificity an lantir bawk. Carbaryl hydrolase leh hydrolase dangte hi Gram-negative bacteria member-te periplasm (transmembrane)-a awm anga ngaih an ni (Kamini et al., 2018). Carbaryl hian amide leh ester linkage a nei vek a; chuvangin esterase emaw amidase emaw hmangin hydrolyze in 1-naphthol a siam thei a ni. Rhizobium rhizobium strain AC10023 leh Arthrobacter strain RC100-a Carbaryl te hi esterase leh amidase angin an thawk tih an sawi a. Arthrobacter strain RC100-a carbaryl pawh hi amidase angin a thawk bawk. RC100 hian N-methylcarbamate class insecticide pali carbaryl, methomyl, mefenamic acid leh XMC te chu hydrolyze a ti thei tih hmuhchhuah a ni (Hayaatsu et al., 2001). Pseudomonas sp.-a CH a awm tih report a ni. C5pp hian carbaryl (100% activity) leh 1-naphthyl acetate (36% activity)-ah hna a thawk thei a, mahse 1-naphthylacetamide-ah erawh a thawk thei lo a, hei hian esterase a nihzia a tilang a ni (Trivedi et al., 2016).
Biochemical study, enzyme regulation pattern leh genetic analysis te chuan naphthalene tihchhiatna genes te hi inducible regulatory unit emaw “operons” pahnih atanga siam a ni tih hmuhchhuah a ni a, chungte chu nah (“upstream pathway”, naphthalene chu salicylic acid ah a chantir) leh sal (“downstream pathway”, salicylic acid chu catechol hmanga central carbon pathway ah a chantir) te an ni. Salicylic acid leh a analogues te hian inducer angin hna an thawk thei a ni (Shamsuzzaman and Barnsley, 1974). Glucose emaw organic acid emaw a awm chuan operon chu a repress a ni. Figure 5-ah hian naphthalene tihchhiatna (operon form-a) genetic organization kimchang tak kan hmu a. Nah gene (ndo/pah/dox) hming vuah chi hrang hrang/form engemaw zat sawi a ni tawh a, Pseudomonas chi zawng zawng zingah sequence homology sang tak (90%) an nei tih hmuhchhuah a ni (Abbasian et al., 2016). Naphthalene upstream pathway-a genes te chu a tlangpuiin Figure 5A-a kan hmuh angin consensus order-in an dah a. Gene dang nahQ pawh naphthalene metabolism-ah a inrawlh tih an sawi a, nahC leh nahE inkarah a awm tlangpui a, mahse a hnathawh tak tak erawh chu hriat chian a la ni lo. Chutiang bawkin naphthalene-sensitive chemotaxis siamtu nahY gene chu member thenkhatah nah operon distal end-ah hmuh a ni bawk. Ralstonia sp.-ah chuan glutathione S-transferase (gsh) encoding U2 gene chu nahAa leh nahAb inkarah a awm tih hmuhchhuah a ni a, mahse naphthalene hman danah erawh a nghawng lo (Zylstra et al., 1997).
Figure 5. Bacteria chi hrang hrang zinga naphthalene tihchhiat laia genetic organization leh diversity hmuhchhuah; (A) Naphthalene kawng chunglam, naphthalene chu salicylic acid-a a inthlak danglamna; (B) Naphthalene kalna hnuai lam, salicylic acid chu catechol kaltlangin central carbon kalna kawngah; (C) salicylic acid chu gentisate kaltlangin central carbon pathway-ah a lut thin.
“Lower pathway” (sal operon) hi a tlangpuiin nahGTHINLMOKJ atanga siam a ni a, catechol metaring cleavage pathway hmangin salicylate chu pyruvate leh acetaldehyde ah a chantir thin. NahG gene (encoding salicylate hydroxylase) chu operon proximal end-ah a awm tih hmuhchhuah a ni (Fig. 5B). Naphthalene tichhe thei chi dangte nena khaikhin chuan P. putida CSV86-ah hian nah leh sal operon te hi tandem leh inzawm tlat (7.5 kb vel) an ni. Gram-negative bacteria thenkhatah chuan Ralstonia sp. U2, Polaromonas naphthalenivorans CJ2, leh P. putida AK5 te hian naphthalene hi central carbon metabolite angin gentisate pathway (sgp/nag operon angin) hmangin a metabolize a ni. Gene cassette hi a tlangpuiin nagAaGHAbAcAdBFCQEDJI angin a lang a, chutah chuan nagR (LysR-type regulator encoding) chu a chung lam tawp lamah a awm a (Figure 5C).
Carbaryl hi central carbon cycle ah hian 1-naphthol, 1,2-dihydroxynaphthalene, salicylic acid leh gentisic acid te metabolism hmangin a lut thin (Figure 3). Genetic leh metabolic study atanga chhut chuan he kawng hi “upstream” (carbaryl chu salicylic acid-ah a chantir), “middle” (salicylic acid chu gentisic acid-ah a chantir), leh “downstream” (gentisic acid chu central carbon pathway intermediates-ah a chantir) tiin then a rawt a ni (Singh et al., 2013). C5pp (supercontig A, 76.3 kb) genomic analysis-ah chuan mcbACBDEF gene hi carbaryl chu salicylic acid-a chantirnaah a inrawlh tih hmuhchhuah a ni a, chumi hnuah mcbIJKL chu salicylic acid chu gentisic acid-ah a chantir a, mcbOQP chuan gentisic acid chu central carbon intermediate-ah a chantir (fumarate leh pyruvate, Trivedi et al., 2016) (Figure 6) a ni.
Aromatic hydrocarbons (naphthalene leh salicylic acid te pawh tel) tihchhiatna atana inrawlh enzyme te chu a inmil compound te hian an tichhuak thei a, carbon source awlsam tak tak glucose emaw organic acids emaw hmangin an titawp thei tih an sawi (Shingler, 2003; Phale et al., 2019, 2020). Naphthalene leh a derivatives te metabolic pathway hrang hrang zingah hian naphthalene leh carbaryl te regulatory features hi eng emaw chen zirchian a ni tawh a. Naphthalene tan chuan upstream leh downstream pathway-a gene awmte chu NahR, LysR-type trans-acting positive regulator hmanga enkawl a ni. Salicylic acid hmanga nah gene induction leh a hnu lama high-level expression atan a mamawh a ni (Yen and Gunsalus, 1982). Chubakah, zirchianna hrang hrangah chuan integrative host factor (IHF) leh XylR (sigma 54-dependent transcriptional regulator) te pawh hi naphthalene metabolism-a genes transcriptional activation atan a pawimawh hle tih hmuhchhuah a ni bawk (Ramos et al., 1997). Zirna hrang hrangah chuan catechol meta-ring opening pathway-a enzyme, catechol 2,3-dioxygenase te chu naphthalene leh/ emaw salicylic acid awmnaah an induce tih hmuhchhuah a ni (Basu et al., 2006). Zirna hrang hrangah chuan catechol ortho-ring opening pathway-a enzyme, catechol 1,2-dioxygenase te chu benzoic acid leh cis,cis-muconate awmnaah an induce tih hmuhchhuah a ni (Parsek et al., 1994; Tover et al., 2001).
Strain C5pp-ah hian gene panga, mcbG, mcbH, mcbN, mcbR leh mcbS te hian carbaryl chhiatna control tura mawhphurtu transcriptional regulator LysR/TetR chhungkaw zinga mi regulator an encode a ni. Homologous gene mcbG hi Burkholderia RP00725-a phenanthrene metabolism-a inrawlh LysR-type regulator PhnS (58% amino acid identity) nen a inzawm tlat tih hmuhchhuah a ni (Trivedi et al., 2016). mcbH gene hi intermediate pathway (salicylic acid chu gentisic acid-a chantir)-ah a inrawlh tih hmuhchhuah a ni a, Pseudomonas leh Burkholderia-a LysR-type transcriptional regulator NagR/DntR/NahR-ah a tel tih hmuhchhuah a ni. He chhungkaw member-te hian salicylic acid hi degradation genes induction atana effector molecule bik anga an hriat thu an sawi. A lehlamah chuan downstream pathway (gentisate-central carbon pathway metabolites)-ah hian LysR leh TetR type transcriptional regulator-a tel gene pathum mcbN, mcbR leh mcbS te hmuhchhuah a ni.
Prokaryote-ah chuan plasmid, transposons, prophages, genomic islands, leh integrative conjugative elements (ICE) hmanga horizontal gene transfer process (acquisition, exchange, or transfer) te hi bacteria genome-a plasticity awm chhan lian ber a ni a, chu chuan function/trait bik neih emaw hloh emaw a thlen thin. Bacteria te chu boruak hrang hrangah rang takin an insiamrem thei a, host tan adaptive metabolic advantages awm thei, aromatic compounds tihchhiat te a pe thei a ni. Metabolic changes hi degradation operons, an regulatory mechanisms, leh enzyme specificities te fine-tuning hmangin a thleng fo thin a, hei hian aromatic compound hrang hrang degradation a ti awlsam hle (Nojiri et al., 2004; Phale et al., 2019, 2020). Naphthalene tihchhiatna atana gene cassette te hi mobile element hrang hrang plasmid (conjugative leh non-conjugative), transposon, genome, ICE, leh bacteria chi hrang hrang inzawmkhawmah te dah a ni tih hmuhchhuah a ni (Figure 5). Pseudomonas G7-ah chuan plasmid NAH7-a nah leh sal operon te hi orientation inangah an transcribe a, mobilization atan transposase Tn4653 mamawh transposon chhia zinga mi an ni (Sota et al., 2006). Pseudomonas strain NCIB9816-4-ah chuan conjugative plasmid pDTG1-ah chuan operon pahnih (15 kb vel a inhlat) angin gene hi hmuh a ni a, chu chu kawng hrang hranga transcribe a ni (Dennis and Zylstra, 2004). Pseudomonas putida strain AK5 ah chuan non-conjugative plasmid pAK5 hian naphthalene tihchhiatna atana mawhphurtu enzyme chu gentisate pathway hmangin a encode a (Izmalkova et al., 2013). Pseudomonas strain PMD-1-ah chuan nah operon hi chromosome-ah a awm a, sal operon erawh chu conjugative plasmid pMWD-1-ah a awm thung (Zuniga et al., 1981). Mahse, Pseudomonas stutzeri AN10-ah chuan naphthalene degradation genes (nah leh sal operons) zawng zawng hi chromosome-ah an awm vek a, transposition, recombination, leh rearrangement events hmanga recruit an ni tih a rin a ni (Bosch et al., 2000). Pseudomonas sp.-ah chuan a awm a. CSV86, nah leh sal operon te hi genome ah ICE (ICECSV86) angin an awm a. Structure hi tRNAGly hmanga venhim a ni a, chu chu direct repeats hmanga recombination/attachment sites (attR leh attL) leh tRNAGly tawp pahniha awm phage ang chi integrase hmanga ven a ni a, chuvangin structure lamah chuan ICEclc element (ICEclcB13 in Pseudomonas knackmusii for chlorocatechol degradation) nen a inang a ni. ICE-a genes te chu conjugation hmangin transfer frequency hniam tak (10-8) hmangin transfer theih a ni tih an sawi a, chu chuan degradation property chu a dawngtu hnenah a transfer thei a ni (Basu and Phale, 2008; Phale et al., 2019).
Carbaryl tihchhiatna atana mawhphurtu gene tam zawk hi plasmid-ah a awm a. Arthrobacter sp. tih hi a awm a. RC100 hian plasmid pathum (pRC1, pRC2 leh pRC300) a nei a, chung zinga conjugative plasmid pahnih, pRC1 leh pRC2 te chuan carbaryl chu gentisate-a chantirtu enzyme te chu an encode a ni. A lehlamah chuan gentisate chu central carbon metabolites-a a chantirna atana inrawlh enzyme te chu chromosome-ah an awm a (Hayaatsu et al., 1999). Bacteria chi hrang hrang Rhizobium a ni. Carbaryl 1-naphthol-a chantirna atana hman strain AC100-ah hian plasmid pAC200 a awm a, hei hian insertion element ang chi sequence (istA leh istB)-in a hual vel Tnceh transposon-a tel angin CH encode tu cehA gene a keng tel a ni (Hashimoto et al., 2002). Sphingomonas strain CF06-ah chuan carbaryl tihchhiatna gene hi plasmid pangaah a awm nia rin a ni a, chungte chu pCF01, pCF02, pCF03, pCF04, leh pCF05 te an ni. Heng plasmid te DNA homology hi a sang hle a, hei hian gene duplication event a awm tih a tilang a ni (Feng et al., 1997). Pseudomonas chi hnih atanga siam carbaryl-degrading symbiont-ah chuan strain 50581-ah hian mcd carbaryl hydrolase gene encode tu conjugative plasmid pCD1 (50 kb) a awm a, strain 50552-a conjugative plasmid erawh chuan 1-naphthol-degrading enzyme (Chapalamadugu leh Chaudhry, 1991-a ziah a ni). Achromobacter strain WM111 ah chuan mcd furadan hydrolase gene hi 100 kb plasmid (pPDL11) ah a awm a. He gene hi geographical region hrang hrang atanga bacteria hrang hranga plasmid hrang hrang (100, 105, 115 emaw 124 kb) ah a awm tih hmuhchhuah a ni (Parekh et al., 1995). Pseudomonas sp.-ah chuan a awm a. C5pp, carbaryl tihchhiatna atana mawhphurtu gene zawng zawng hi genome 76.3 kb sequence-a zauah an awm vek a ni (Trivedi et al., 2016). Genome analysis (6.15 Mb) ah chuan MGE 42 leh GEI 36 a awm tih hmuhchhuah a ni a, chung zinga MGE 17 chu supercontig A (76.3 kb)-ah awmin, average asymmetric G+C content (54–60 mol%) a awm a, hei hian horizontal gene transfer events a awm theih thu a tarlang (Trivedi et al., 2016). P. putida XWY-1 hian carbaryl-degrading genes inrem dan ang chiah hi a lantir a, mahse heng genes te hi plasmid-ah an awm a ni (Zhu et al., 2019).
Biochemical leh genomic level-a metabolic efficiency bakah hian microorganisms te hian property dang emaw response dang emaw chemotaxis, cell surface modification properties, compartmentalization, preferential utilization, biosurfactant production, etc. te an nei bawk a, hei hian boruak bawlhhlawh takah aromatic pollutants te chu efficient zawka metabolize turin a pui a ni (Figure 7).
Figure 7. Ramdang bawlhhlawh compound te biodegradation tha tak neih theihna tura ideal aromatic hydrocarbon-degrading bacteria te cellular response strategy hrang hrang.
Chemotactic response hi heterogeneously polluted ecosystem-a organic pollutants tihchhiatna tichaktuah ngaih a ni. (2002) te chuan Pseudomonas sp. G7 to naphthalene hian tui chhunga naphthalene tihchhiatna rate a tisang a ni. Wild-type strain G7 hian chemotaxis nei lo mutant strain aiin naphthalene a tichhe rang zawk hle. NahY protein (538 amino acids with membrane topology) hi NAH7 plasmid-a metacleavage pathway genes nen co-transcribed a ni tih hmuhchhuah a ni a, chemotaxis transducers ang bawkin he protein hian naphthalene tihchhiatna chemoreceptor angin a thawk niin a lang (Grimm and Harwood 1997). Hansel leh a thawhpuiten an zirchianna dang pakhat chuan. (2009) te chuan protein hi chemotactic a ni a, mahse a degradation rate a sang hle tih an hmuchhuak. (2011) te chuan Pseudomonas (P. putida) hian gaseous naphthalene a chemotactic response an hmuchhuak a, gas phase diffusion hian naphthalene chu cells ah a luang chhuak zel a, chu chuan cells te chemotactic response a control a ni. He chemotactic behavior hi zirchiangtute chuan hmang tangkaiin microbes te chu an engineer a, chu chuan a chhe chakna a ti sang ang. Zirna hrang hrangah chuan chemosensory pathways hian cellular function dang cell division, cell cycle regulation, leh biofilm formation te pawh a tidanglam a, chu chuan degradation rate control-na kawngah a pui hle tih hmuhchhuah a ni. Mahse, he property (chemotaxis) hi efficient degradation atana hman tangkai hi bottleneck engemaw zatin a tikhawtlai a ni. Harsatna lian ber berte chu: (a) paralogous receptor hrang hrangin compound/ligand inang an hre thei a; (b) receptor dang awmna, chu chu energetic tropism; (c) Receptor chhungkaw khata sensory domain-a sequence danglamna lian tham; leh (d) bacteria sensor protein lian ber berte chungchanga hriat tur awm lohna (Ortega et al., 2017; Martin-Mora et al., 2018). A châng chuan, aromatic hydrocarbons biodegradation hian metabolite/intermediate tam tak a siam chhuak a, hei hi bacteria pawl pakhat tan chuan chemotactic ni mahse midang tan chuan repulsive tak a ni thei a, hei hian a kalphung a ti buai zual hle. Ligands (aromatic hydrocarbons) leh chemical receptor inzawmna hriat theih nan Pseudomonas putida leh Escherichia coli sensor leh signaling domain te fuse-in hybrid sensor protein (PcaY, McfR, leh NahY) kan siam a, chungte chuan aromatic acids, TCA intermediates, leh naphthalene receptor te chu an target a ni (Luu et al., leh naphthalene te chu an target a ni (Luu et al., 2019 a ni).
Naphthalene leh polycyclic aromatic hydrocarbons (PAH) dangte nghawng hnuaiah hian bacterial membrane structure leh microorganisms te integrity-ah danglamna nasa tak a awm a. Zirna hrang hrangah naphthalene hian hydrophobic interaction hmangin acyl chain inzawmna a tibuai a, chu chuan membrane swelling leh fluidity a tipung tih hmuhchhuah a ni (Sikkema et al., 1995). He thil tha lo tak hi do let turin bacteria te hian iso/anteiso branched-chain fatty acids inkar ratio leh fatty acid composition te chu an thlak danglam a, cis-unsaturated fatty acids te chu a inmil trans-isomers ah isomerize in membrane fluidity an tidanglam thin (Heipieper and de Bont, 1994). Naphthalene hmanga enkawl Pseudomonas stutzeri-ah chuan saturated to unsaturated fatty acid ratio chu 1.1 aṭangin 2.1-ah a pung a, Pseudomonas JS150-ah erawh chuan 7.5 aṭangin 12.0-ah a pung thung (Mrozik et al., 2004). Naphthalene-a an tihpun chuan Achromobacter KAs 3–5 cells te hian naphthalene crystals vel ah cell aggregation an lantir a, cell surface charge tlahniam (-22.5 atanga -2.5 mV) te chu cytoplasmic condensation leh vacuolization nen a inzawm a, hei hian cell structure leh cell surface property inthlak danglamna a tilang a ni (Mohapatra et al., 2019). Cellular/surface inthlak danglamna hi aromatic pollutants lakluhna tha zawk nen direct-in inzawm mahse, bioengineering strategy kaihhnawih te chu uluk taka siam that a la ni lo. Biological process tihchangtlun nan cell shape manipulation hi hman a ni tlem hle (Volke and Nikel, 2018). Cell inthenna tichhe thei genes deletion hian cell morphology a tidanglam thin. Cell inthenna tichhe thei genes deletion hian cell morphology a tidanglam thin. Bacillus subtilis-ah chuan cell septum protein SepF hi septum siamnaah a inrawlh tih hmuhchhuah a ni a, a hnu lama cell inthenna step hrang hrang atan a mamawh a, mahse gene pawimawh tak a ni lo. Bacillus subtilis-a peptide glycan hydrolases encode tu genes deletion hian cell elongation a thlen a, specific growth rate a tisang a, enzyme production capacity a ti sang bawk (Cui et al., 2018).
Pseudomonas strain C5pp leh C7 te efficient taka tihchhiat theihna turin carbaryl degradation pathway compartmentalization siam a rawt a ni (Kamini et al., 2018). Carbaryl hi periplasmic space-ah outer membrane septum kaltlangin leh/ emaw diffusible porins kaltlangin a phurh luh thu an rawt a ni. CH hi periplasmic enzyme a ni a, carbaryl hydrolysis chu 1-naphthol-ah a tichak a, chu chu a stable zawk a, hydrophobic zawk leh toxic zawk a ni. CH hi periplasm-ah a awm a, carbaryl nen affinity hniam tak a nei a, chu chuan 1-naphthol siamna a control a, chu chuan cell-a a pungkhawm tur a veng a, cell-a a toxicity a tihtlem phah bawk (Kamini et al., 2018). Chuta chhuak 1-naphthol chu inner membrane kaltlangin cytoplasm chhungah partitioning leh/or diffusion hmangin a phur lut a, chutah chuan high-affinity enzyme 1NH hmangin 1,2-dihydroxynaphthalene-ah hydroxylated a ni a, central carbon pathway-ah metabolism dang a awm lehzual a ni.
Microorganisms hian xenobiotic carbon sources tihchhiat theihna genetic leh metabolic capabilities nei mahse, an hman dan hierarchical structure (ie, preferential use of simple over complex carbon sources) hi biodegradation daltu lian tak a ni. Carbon source awlsam tak tak awmna leh hman hian PAHs ang chi carbon source complex/non-preferred tichhe thei enzyme encoding genes te chu a downregulate a ni. Entirna zirchian tha tak chu glucose leh lactose te hi Escherichia coli-a co-fed an nih chuan glucose hi lactose aiin a hmang tangkai zawk tih hi a ni (Jacob and Monod, 1965). Pseudomonas hian PAH chi hrang hrang leh xenobiotic compound te chu carbon source atan a tichhe thei niin an sawi. Pseudomonas-a carbon source hman dan hierarchy chu organic acids > glucose > aromatic compounds a ni (Hylemon leh Phibbs, 1972; Collier et al., 1996). Mahse, exception a awm. Ngaihven awm tak chu Pseudomonas sp. CSV86 hian hierarchical structure danglam tak a lantir a, glucose aiin aromatic hydrocarbons (benzoic acid, naphthalene, etc.) a hmang duh zawk a, aromatic hydrocarbons chu organic acids nen a co-metabolize a ni (Basu et al., 2006). He bacterium ah hian aromatic hydrocarbons tihchhiat leh phurh chhuahna tur genes te hi carbon source pahnihna glucose emaw organic acids emaw awmnaah pawh downregulated a ni lo. Glucose leh aromatic hydrocarbons medium-a an tihpun chuan glucose transport leh metabolism atana genes te chu downregulated a ni tih hmuhchhuah a ni a, log phase hmasa berah aromatic hydrocarbons hman a ni a, log phase pahnihnaah glucose hman a ni bawk (Basu et al., 2006; Choudhary et al., 2017). A lehlamah chuan organic acid awmna hian aromatic hydrocarbon metabolism expression a nghawng lo a, chuvangin he bacterium hi biodegradation study atana candidate strain a nih beisei a ni (Phale et al., 2020).
Hydrocarbon biotransformation hian microorganisms-a antioxidant enzymes te oxidative stress leh upregulation a thlen thei tih hriat lar tak a ni. Stationary phase cell-ah te leh toxic compound awmnaah te naphthalene biodegradation tha lo tak hian reactive oxygen species (ROS) a siam chhuak thin (Kang et al. 2006). Naphthalene tichhe thei enzyme-ah hian iron-sulphur clusters a awm avangin oxidative stress hnuaiah heme leh iron-sulphur protein-a iron awmte chu oxidized a ni ang a, chu chuan protein inactivation a thlen ang. Ferredoxin-NADP+ reductase (Fpr) hian superoxide dismutase (SOD) nen NADP+/NADPH leh ferredoxin emaw flavodoxin molecule pahnih inkara reversible redox reaction a mediate a, chu chuan ROS chu a scavenging a, oxidative stress hnuaiah iron-sulphur center chu a siam tha leh a ni (Li et al. 2006). Pseudomonas-a Fpr leh SodA (SOD) te hi oxidative stress vangin a awm thei tih an sawi a, naphthalene-added condition hnuaia an than laiin Pseudomonas strain pali (O1, W1, As1, leh G1)-ah SOD leh catalase activity tihpun hmuh a ni bawk (Kang et al., 2006). Zirna hrang hrangah chuan antioxidants ascorbic acid emaw ferrous iron (Fe2+) te dah tel hian naphthalene hi a than chakna a tisang thei tih hmuhchhuah a ni. Rhodococcus erythropolis chu naphthalene medium-a a lo thang lian chuan oxidative stress-related cytochrome P450 genes transcription a tipung a, chung zingah chuan sodA (Fe/Mn superoxide dismutase), sodC (Cu/Zn superoxide dismutase), leh recA te pawh a tel a ni (Sazykin et al., 2019). Naphthalene-a cultured Pseudomonas cells te comparative quantitative proteomic analysis hmangin oxidative stress response nena inzawm protein hrang hrangte upregulation chu stress coping strategy a ni tih hmuhchhuah a ni (Herbst et al., 2013).
Microorganisms hian hydrophobic carbon sources hnathawhna hnuaiah biosurfactants an siam chhuak tih an sawi. Heng surfactant te hi amphiphilic surface active compound an ni a, oil-water emaw air-water interface-ah aggregate an siam thei a ni. Hei hian pseudo-solubilization a tichak a, aromatic hydrocarbons adsorption a ti awlsam a, chu chuan biodegradation tha tak a thlen a ni (Rahman et al., 2002). Heng property te avang hian biosurfactant hi industry hrang hrangah hman a ni nasa hle. Bacteria culture-a chemical surfactant emaw biosurfactant emaw dah tel hian hydrocarbon tihchhiatna efficiency leh rate a tisang thei a ni. Biosurfactant zingah hian Pseudomonas aeruginosa siam rhamnolipids te hi nasa takin zirchian a ni a, an characteristic pawh an zirchiang tawh bawk (Hisatsuka et al., 1971; Rahman et al., 2002). Tin, biosurfactant chi dangte chu lipopeptides (Pseudomonas fluorescens atanga mucins), emulsifier 378 (Pseudomonas fluorescens atanga lak) (Rosenberg leh Ron, 1999), Rhodococcus atanga trehalose disaccharide lipids (Ramdahl, 1985), Bacillus atanga lichenin (Saraswathy leh Hallberg, 2002), leh Bacillus subtilis (Siegmund leh Wagner, 1991) leh Bacillus amyloliquefaciens (Zhi et al., 2017) atanga surfactant te a awm bawk. Heng surfactant chak tak takte hian surface tension 72 dynes/cm atanga 30 dynes/cm aia tlem loah a tihhniam tih hmuhchhuah a ni a, hei hian hydrocarbon absorption tha zawk a siam thei a ni. Pseudomonas, Bacillus, Rhodococcus, Burkholderia leh bacteria chi dangte hian naphthalene leh methylnaphthalene media-a an chin chuan rhamnolipid leh glycolipid-based biosurfactant hrang hrang an siam thei tih an sawi (Kanga et al., 1997; Puntus et al., 2005). Pseudomonas maltophilia CSV89 hi naphthoic acid ang chi aromatic compound-a a chin chuan extracellular biosurfactant Biosur-Pm a siam thei a ni (Phale et al., 1995). Biosur-Pm siamna kinetics atanga a lan dan chuan a siam chhuahna chu a thanna leh pH a innghat a ni. Neutral pH-a cell-te siam Biosur-Pm chu pH 8.5-a Biosur-Pm siam chhuah zat aiin a tam zawk tih hmuhchhuah a ni. pH 8.5-a seilian cell-te chu pH 7.0-a seilian cell aiin hydrophobic an ni zawk a, aromatic leh aliphatic compound-te tan affinity sang zawk an nei bawk. Rhodococcus spp. ah chuan a awm a. N6, carbon to nitrogen (C:N) ratio sang zawk leh iron limitation te hi extracellular biosurfactant siamna atana dinhmun tha ber a ni (Mutalik et al., 2008). Strain leh fermentation tihchangtlun hmangin biosurfactants (surfactins) biosynthesis tihchangtlun tum a ni. Mahse, culture medium-a surfactant titer a hniam (1.0 g/L), hei hian large-scale production atan harsatna a siam a ni (Jiao et al., 2017; Wu et al., 2019). Chuvangin a biosynthesis tihchangtlun nan genetic engineering methods hman a ni ta a ni. Mahse, a engineering modification hi operon lian tham (∼25 kb) leh quorum sensing system-a biosynthetic regulation complex tak avang hian a harsa hle (Jiao et al., 2017; Wu et al., 2019). Bacillus bacteria-ah hian genetic engineering modification engemaw zat tih a ni tawh a, a tum ber chu promoter (srfA operon) thlak a, surfactin export protein YerP leh regulatory factors ComX leh PhrC te overexpressing hmanga surfactin siam chhuah tihpun tumna a ni (Jiao et al., 2017). Mahse, heng genetic engineering methods te hian genetic modification pakhat emaw, tlemte emaw chauh an nei a, sumdawnna atana siam chhuah an la thleng lo. Chuvangin, hriatna hmanga optimization methods zirchian belh a ngai a ni.
PAH biodegradation zirchianna hi standard laboratory condition hnuaiah neih a ni ber. Mahse, bawlhhlawh awmna hmunah emaw, boruak bawlhhlawh hmunah emaw chuan abiotic leh biotic factor tam tak (temperature, pH, oxygen, nutrient awm theihna, substrate bioavailability, xenobiotics dang, end-product inhibition, etc.) te hian microorganisms te degradative capacity a tidanglam a, a nghawng tih hmuhchhuah a ni.
Temperature hian PAH biodegradation-ah nghawng lian tak a nei a ni. Temperature a san chuan dissolved oxygen concentration a tlahniam a, hei hian aerobic microorganisms te metabolism a nghawng a, hydroxylation emaw ring cleavage reaction titu oxygenases te substrate pakhat atan molecular oxygen an mamawh avangin. Temperature sang hian parent PAHs te chu toxic compound ah a chantir a, chu chuan biodegradation a titawp tih hriat a ni fo thin (Muller et al., 1998).
PAH bawlhhlawh tam tak chuan pH value sang tak an nei tih hriat a ni a, chu chu acid mine drainage bawlhhlawhna hmun (pH 1–4) leh natural gas/coal gasification hmun alkaline leachate (pH 8–12) hmanga tihbawlhhlawh te hi a ni. Heng dinhmunte hian biodegradation process nasa takin a nghawng thei a ni. Chuvangin, bioremediation atana microorganism hman hmain, alkaline leilung atan ammonium sulfate emaw ammonium nitrate emaw, acidic site atan calcium carbonate emaw magnesium carbonate emaw hmanga liming emaw, chemical tha tak tak (oxidation-reduction potential hniam tak atanga hniam tak nei) dah tel a tha (Bowlen et al. 1995; Gupta and Sar 2020).
A natna hmuna oxygen supply hi PAH biodegradation rate limiting factor a ni. Environment redox condition avang hian in situ bioremediation process-ah hian pawn lam atanga oxygen luh a ngai tlangpui (tilling, air sparging, leh chemical addition) (Pardieck et al., 1992). Odenkranz leh a thawhpuiten an sawi. (1996) te chuan aquifer bawlhhlawh takah magnesium peroxide (oxygen releasing compound) dah belh chuan BTEX compound te chu bioremediate takin a ti tha thei tih an hmuchhuak a. Zirna dang pakhat chuan bioremediation tha tak neih theih nan sodium nitrate inject a, extraction well siamin contaminated aquifer-a phenol leh BTEX in situ degradation a zirchiang bawk (Bewley and Webb, 2001).