Biodegradation of HCB

Bio abasement of HCB1-2-1- abjection of HCB chthonic anaerobiotic conditionIn the past decade, the usage of HCB prohibited in many country but HCB has been found as hazardous pollutants in many places worldwide. Bio degradation of HCB is possible in environmental low anaerobic conditions such as sodium, groundwater and soil but the progress is very soft (Beurskens and others, 1992 Chang and others, 1997). Some reports documented about biodegradation in sediments (Chen and others, 2002 Chen and others, 2004 Hirano and others, 2007 Pavlostathis and Prytula, 2000 Prytula and Pavlostathis, 1996), soil (Watanabe and Yoshikawa, 2008). Degradation of CLD2 in anaerobic sewage sludge was reported by (Fathepure and others, 1988), The authors observed greater than 90% pesticide removal after 3 weeks. The besides Three strains of bacteria capability of degrading Hexachlorobenzene via reductive dechlorination stand been single out (Ta and others, 2011), that including Dehalobium chloroco ercia DF-1 (Wu and others, 2002), Dehalococcoides sp. strain CBDB1 and Dehalococcoides ethenogenes strain 195 (Adrian and others, 2000 Fennell and others, 2004 Tas, 2009 Ta and others, 2009). 1-2-2- Metabolites and Mechanism of anaerobiotic DechlorinationAnaerobic degradation reductive dechlorination of HCB was first reported in 1987 (Fathepure and others, 1988). So far, the pathway that is known for the microbic degradation of HCB under anaerobic canditions by coupling reductive dehalogenation to electron transport (Beurskens and others, 1994 Chen and others, 2000 Hirano and others, 2007 Ta and others, 2011). Chlorinated aromatics can serve as electron acceptors (Fathepure and others, 1988). Reductive dechlorination pathways is shown in dactyl 1 and HCB were dechlorinated via 1,2,3,5-and 1,2,4,5-tetrachIorobenzene (TeCB), 1,3,5- and 1,2,4-TCB , 1,2,4-TCB3 and 1,3-DCB4 . they are final dechlorination products (Beurskens and others, 1992 Boyd and others, 1987 Fathepure and others, 1988 Holliger and others, 1992).1-3- Biodegradation of dichlorodiphenyltrichloroethane51-3-1- Degradation of DDT under anaerobic conditionDDT was the first synthetic insecticide. Nowadays, use of this persistent organic pollutants is prohibited in most countries, but still DDT is ubiquitous in the environment all (Purnomo and others, 2011 Sudharshan and others, 2012). DDT can be biodegradation or mineralized by multistep processes in twain aerobic and anaerobic condition. For example sediments capibilty of utilizing persistent pesticides and degradation even mineralized by aerobic and anaerobic degradation (Fang and others, 2014). Thus far, species within the genera Pseudomonas (Chacko and Lockwood, 1967 Kamanavalli and Ninnekar, 2004), Sphingomonas (Chacko and Lockwood, 1967 Fang and others, 2014), Desulfomonile tiedjei (DeWeerd and others, 1990) and Eubacterium limosum (ATCC 8486) is isolated from the human intestine (Yim and others, 2008), and Alcaligenes denitrificans (Ahuja an d Kumar, 2003) have been found to metabolize DDT. (Corona-Cruz and others, 1999), reported anaerobic coupled with aerobic biodegradation of DDT and maximum DDT degradation of 84.4 %.1-3-2- Metabolites and Mechanism of Anaerobic DechlorinationBiodegradation pathway of DDT is multistep process in anaerobic environment, involving reductive dechlorination, dioxygenation, hydrogenation, hydroxylation, decarboxylation, hydrolysis (a major transformation pathway in soil and water in the presence of H2O, H+, and OH ), and meta- circle cleavage reactions. Biodegradation pathway of DDT is multistep process in anaerobic environment involving reductive dechlorination such as three degradation step (DDTDDD,DDE6), hydrogenation, dioxygenation, hydroxylation, decarboxylation and meta-ring cleavage reactions(Rangachary and others, 2012). That is distinguishable from the degradation pathways for anaerobic biodegradation but high-order metabolites such as DDA, DDOH7 and DDNU (Aislabie and others, 19 97). (Wedemeyer, 1967), reported first metabolic pathways for DDT by aerobacter aerogenes that shown at the bottomDDT DDD8 DDMU9 DDMS10 DDNU11 DDA12 DBP13, or DDT DDE.Researches were lack of information about DDT degradation. Later, (Planche and others, 1979) indicted DDE could be debased to DDMU by a microcosm under anaerobic sediments.biodegradation pathway in sediment shown on figure 2. DDT and its metabolites in the sedimentDDT DDD DDMS and DDE DDMU (Li and others, 2010 Quensen and others, 2001 Sudharshan and others, 2012) and the relative transformation rates of DDT, DDE, and DDD is DDTDDDDDE (Huang and others, 2001), so DDD was the major biodegradation product of DDT under anaerobic environments (Mwangi and others, 2010 Yu and others, 2011). DDT metabolic reports in human intestinal gut by (Yim and others, 2008), that Eubacterium limosum transformed DDT completely to DDD and used DDT as electron donors.1-4- Biodegradation of heptachlor1-4-1- Degradation of heptachlor u nder anaerobic conditionAnaerobic degradation reductive dechlorination of HCB was first reported in 1987 (Fathepure and others, 1988). So far, the pathway that is known for the microbial degradation of HCB under anaerobic canditions by coupling reductive dehalogenation to electron transport (Beurskens and others, 1994 Chen and others, 2000 Hirano and others, 2007 Ta and others, 2011). Chlorinated aromatics can serve as electron acceptors (Fathepure and others, 1988). Reductive dechlorination pathways is shown in figure 1 and HCB were dechlorinated via 1,2,3,5-and 1,2,4,5-tetrachIorobenzene (TeCB), 1,3,5- and 1,2,4-TCB , 1,2,4-TCB3 and 1,3-DCB4 . they are final dechlorination products (Beurskens and others, 1992 Boyd and others, 1987 Fathepure and others, 1988 Holliger and others, 1992). Heptachlor used as insecticide. Heptachlor is mostly persistent in environment (Sakai and others, 2008). Under anaerobic conditions, heptachlor is showed only limited conversion (Hill and McCarty, 19 67). The entropy available on this substance indicate that heptachlor is degraded for more than several years in soil (Lichtenstein and others, 1970 Mahugija, 2014 Miles and others, 1969). (Sethunathan and Yoshida, 1973), this paper is a research about clostridium sp. that isolated from flood soil for degradation -BHC and heptachlor.1-4-2- Metabolites and Mechanism of Anaerobic DechlorinationBiotransformation of heptachlor is not easy and simple but occur in both situations anaerobic and aerobic, principally to the stable heptachlor epoxide (Lichtenstein and others, 1970). (Hayashi and others, 2013) , have reported that heptachlor was degraded a small amount to heptachlor epoxide in soil. Figure3 shown this degradation pathway.1-5- Biodegradation of endrin and dieldrin1-5-1-Degradation of endrin and dieldrin under anaerobic conditionOf the year 1960s began studies on biodegradation of endrin and dieldrin that more researches were reported about the aerobic biodegradation (Matsum oto and others, 2009). Biodegradation of dieldrin and endrin was reviewed in 2007 and 1982 (Lal and Saxena, 1982 Matsumoto and others, 2009). (GOWDA and Sethunathan, 1977), studied that endrin proceeded under anaerobic conditions in three soils by radiotracer technique. Thay have reported anaerobic microbial strains could degrade various types of POPs such as ,heptachlor, dieldrin, aldrin, endrin and HCB. These strains isolated from PCB-contaminated sediment. (Baczynski and others, 2004), reported that methanogenic granular sludge could dechlorination of cyclodiene pesticides such as dieldrin and endrin.(Baczynski and others, 2004), studied methanogenic granular sludge with purpose dechlorinate dieldrin and endrin. Biodegradation studies under anaerobic conditions are summarized in Table 2.1-5-2- Metabolites and Mechanism of Anaerobic DechlorinationDeldrin has simple mechanism reported by (Maule and others, 1987) that is the deletion of the chlorine atom from chlorinated hydrocarbon . (Chiu and others, 2005), reported cleaving the epoxide ring by a mechanism of epoxide reduction by anaerobic enrichment culture obtained from river sediment. So, they are the Transformation of deldrin to aldrin then aldrin is converted to two syn- and anti-monodechlorodieldrin metabolites by epoxide reduction. Researches show only two monochlorinated metabolites of endrin under anaerobic transformation so it can say bacteria have a catalyzed role in reductive dehalogenation (Matsumoto and others, 2009).1-6- Biodegradation of lindane and HCH-isomers1-6-1-Degradation of lindane and HCH-isomers under anaerobic conditionLindane and the other HCH isomers have been used in agriculture as a pesticide. There are little knowledge about anaerobic HCH degradation. It has not been reporte on the anaerobic biodegradation of the HCH (Lal and others, 2010). While the four HCH isomers can degrade under anaerobic conditions .Thus far, species within the genera Dehalobacter (Doesburg and others, 2 005), Clostridium spp (Jagnow and others, 1977 MacRae and others, 1969), boron circulans and Bacillus Brevis (Gupta and others, 2000) and two Desulfovibrio species (Boyle and others, 1999), Citrobacter (such as ,C. butyricum, C. pasteurianum and Citrobacter freundii) (inheritance and MacRae, 1977 Heritage and Rae, 1977), Desulfococcus (Elango and others, 2011) and Desulfobacter curvatus (Badea and others, 2009) have been found to metabolize the lindane and HCH-isomers.(Van Eekert and others, 1998), have studied, capable of degrading beta-HCH using a upflow anaerobic sludge blanket (UASB) reactors with methanogenic granular sludges. A number of studies have utilized for degradation isomer-HCH of anaerobic mixed bacterial culture such as (Kohnen and others, 1975) that mixed culture consisting of Bacilli. Mixed culture Clostridia and C. butyricum, C. pasteurianum and Citrobacter freundii. Thay are shown degradation rate in the following order -HCH -HCH -HCH = -HCH (Jagnow and others , 1977). (Pesce and Wunderlin, 2004) isolated bacteria from sediment and have used in aerobic mixed bacterial culture including Bosea thiooxidans and Sphingobacterium paucimobilis, degraded HCH after 3 days.1-6-2- Metabolites and Mechanism of anaerobic Dechlorinationthe mechanism of biotransformation of HCH-isomer and lindane under anaerobic condition is explained with detection of intermediates substance of the presumed pathway. According to papers and reports, intermediates of HCH such as TeCCHs16, PeCCHs17 , PCCHa18 (Buser and Mueller, 1995). (Tsukano and Kobayashi, 1972), abserved TeCCH flooded rice field soils treated with lindan but this intermediates was not found in soils treated with sodium azide or in soils without lindane treatment. suggested two degradation pathway for HCH isomers under anaerobic conditions, Based upon identify the intermediates materialgama-, alfa-HCH PCCHa (with a dechlorination) 1,2-DCB19 1,3-DCB finally CBfor - and -HCH TeCCH 1,2,3-TCB 1,2-DCB 1,4-DCB CB20The other Simpler pathway for the reductive dehalogenation of HCH isHCH TeCCH dichlorocyclohexadiene ( DCCH) finally benzene (Doesburg and others, 2005 Lal and others, 2010). Most papers of anaerobic degradation reported the accumulation of benzene and chlorobenzene (Buser and Mueller, 1995 Middeldorp and others, 1996 Zhu and others, 2005).that Figure3 shown this pathways.1-7- Biodegradation of Methoxychlor1-7-1-Degradation of Methoxychlor under anaerobic conditionMethoxychlor 1,1,1-trichloro-2,2-bis(p-methoxyphenyl) ethane is a hazardous substance and stable for this reason, is one of POPs. Methoxychlor have a half-life Enterobacter amnigenus, Aeromonas hydrophila, Bacillus subtilis,Klebsiella terrigena, Mycobacterium obuense, Acinetobacter calcoaceticus, and Achromobacter. Biodegradation studies of OCPs under anaerobic conditions are summarized in Table 2.Figure 3v Proposed pathway for anaerobic biodegradation of HCH under a) alfa- HCH b) gama and beta- HCH (Does burg and others, 2005 Lal and others, 2010)1-7-2- Metabolites and Mechanism of anaerobic DechlorinationMicrobial species and pathway dechlorination of methoxychlor in the environment are not well-known or there are few reports (Castro and Yoshida, 1971 Masuda and others, 2011b). Enterobacter aerogenes were capable of degrading methoxychlor to DMDD 21 under anaerobic conditions (Mendel and Walton, 1966). Eubacterium limosum is a bacteria from human intestine that has been able degrades of methoxychlor to 1,1-dichloro-2,2-bis(pmethoxyphenyl) ethane (methoxydichlor) (Yim and others, 2008). Also, K. pneumoniae converts methoxychlor to 1,1-dichloro-2,2-bis(4-methoxyphenyl)ethane, de-Cl-MXC (Baarschers and others, 1982).1 hexachlorobenzene (HCB)2 Chlordane (CLD)3 -trichlorobenzene (TCB)4 1,3-dichlorobenzene (1,3-DCB)5 1,1,1-Trichloro-2,2-bis(4-chlorophenyl)ethane (DDT)6 1,1-dichloro-2,2-bis-(p-chlorophenyl)ethylene (DDE)7 2,2-bis(p-chlorophenyl)ethanol (DDOH)8 1,1-dichloro-2,2-bis-(p-chlo rophenyl)ethane (DDD)9 1-chloro-2,2-bis-(p-chlorophenyl)ethylene (DDMU)10 1-chloro-2,2-bis-(p-chlorophenyl)ethane (DDMS)11 2,2-bis(p-chlorophenyl)ethylene (DDNU)12 2,2-bis(p-chlorophenyl)acetic acid (DDA)13 4,4-dichlorobenzophenone (DBP)14 Removal and rate15 Dichlorodiphenyltrichloroethane(DDT)16 tetrachlorocyclohexenes (TeCCHs)17 pentachlorocyclohexenes (PeCCHs)18 pentachlorocyclohexanes (PCCHa)19 dichlorobenzene (DCB )20 Chlorobenzene21 bis(p-methoxyphenyl)-1,1dichloroethane (DMDD)