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Biodegradation and detoxification of textile azo dyes by bacterial consortium under sequential microaerophilic/aerobic processes.

Lade H, Kadam A, Paul D, Govindwar S - EXCLI J (2015)

Bottom Line: RB 5 (0.08 mM), RO 16 (0.06 mM), DR 78 (0.07 mM) and DR 81 (0.09 mM) resulted into the formation of aromatic amines.Additionally, 62-72 % reduction in total organic carbon content was observed in all the dyes decolorized broths under sequential microaerophilic/aerobic processes suggesting the efficacy of method in mineralization of dyes.Notable induction within the levels of azoreductase and NADH-DCIP reductase (97 and 229 % for RB 5, 55 and 160 % for RO 16, 63 and 196 % for DR 78, 108 and 258 % for DR 81) observed under sequential microaerophilic/aerobic processes suggested their critical involvements in the initial breakdown of azo bonds, whereas, a slight increase in the levels of laccase and veratryl alcohol oxidase confirmed subsequent oxidation of formed amines.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Engineering, Konkuk University, Seoul-143-701, Korea.

ABSTRACT
Release of textile azo dyes to the environment is an issue of health concern while the use of microorganisms has proved to be the best option for remediation. Thus, in the present study, a bacterial consortium consisting of Providencia rettgeri strain HSL1 and Pseudomonas sp. SUK1 has been investigated for degradation and detoxification of structurally different azo dyes. The consortium showed 98-99 % decolorization of all the selected azo dyes viz. Reactive Black 5 (RB 5), Reactive Orange 16 (RO 16), Disperse Red 78 (DR 78) and Direct Red 81 (DR 81) within 12 to 30 h at 100 mg L(-1) concentration at 30 ± 0.2 °C under microaerophilic, sequential aerobic/microaerophilic and microaerophilic/aerobic processes. However, decolorization under microaerophilic conditions viz. RB 5 (0.26 mM), RO 16 (0.18 mM), DR 78 (0.20 mM) and DR 81 (0.23 mM) and sequential aerobic/microaerophilic processes viz. RB 5 (0.08 mM), RO 16 (0.06 mM), DR 78 (0.07 mM) and DR 81 (0.09 mM) resulted into the formation of aromatic amines. In distinction, sequential microaerophilic/ aerobic process doesn't show the formation of amines. Additionally, 62-72 % reduction in total organic carbon content was observed in all the dyes decolorized broths under sequential microaerophilic/aerobic processes suggesting the efficacy of method in mineralization of dyes. Notable induction within the levels of azoreductase and NADH-DCIP reductase (97 and 229 % for RB 5, 55 and 160 % for RO 16, 63 and 196 % for DR 78, 108 and 258 % for DR 81) observed under sequential microaerophilic/aerobic processes suggested their critical involvements in the initial breakdown of azo bonds, whereas, a slight increase in the levels of laccase and veratryl alcohol oxidase confirmed subsequent oxidation of formed amines. Also, the acute toxicity assay with Daphnia magna revealed the nontoxic nature of the dye-degraded metabolites under sequential microaerophilic/aerobic processes. As biodegradation under sequential microaerophilic/aerobic process completely detoxified all the selected textile azo dyes, further efforts should be made to implement such methods for large scale dye wastewater treatment technologies.

No MeSH data available.


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Decolorization of azo dyes by bacterial consortium and formation of aromatic amines and TOC reduction under various experimental conditions
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T2: Decolorization of azo dyes by bacterial consortium and formation of aromatic amines and TOC reduction under various experimental conditions

Mentions: The results of the decolorization study showed that, 98-99 % decolorization of all the four dyes was observed within 30 h of incubation under microaerophilic conditions (Table 2(Tab. 2)). However, variation in decolorization time was observed for all the dyes viz. RB 5 (30 h), RO 16 (12 h), DR 78 (18 h) and DR 81 (24 h) and that may be due to the structural differences of azo dyes used (Moosvi et al., 2005[35]). It has been reported that the azo dyes with mono azo bond were more likely to be decolorized faster than those with diazo or triazo groups (Franciscon et al., 2009[15]). For this reason, RO 16 and DR 78, which are both monoazo dyes showed a short decolorization time (12 and 18 h, respectively) and the highly substituted diazo RB 5 and DR 81 showed longer decolorization times (30 and 24 h, respectively). It is suggested that, the azo dyes with a hydroxyl or amino groups were methoxy, sulfo or nitro groups (Nigam et al., 1996[37]). Hence, in the present study variation in decolorization time was observed for all the dyes as these have difference in number of azo bonds and its position. The complete decolorization of all the dyes at microaerophilic conditions suggest that this process favors the decolorization and which may be due to the involvement of reductive enzymes in initial break-down of azo dyes. It was reported that, reductive cleavage of azo bonds (–N=N–) by azoreductase normally occurs in absence or reduced levels of oxygen as in microaerophilic conditions (Chang et al., 2001[5]; Sheth and Dave, 2009[51]). In contrast to the complete decolorization of all the four dyes under microaerophilic condition, the reduced performance only up to 12 % for RB 5, 20 % for RO 16, 22 % for DR 78 and 21 % for DR 81 was achieved under aerobic conditions within the same time and even no complete decolorization was observed in 48 h (Table 2(Tab. 2)). A previous study on aerobic decolorization of azo dyes has also shown that this process is insufficient to completely degrade most of azo dyes (Ogugbue et al., 2012[38]).


Biodegradation and detoxification of textile azo dyes by bacterial consortium under sequential microaerophilic/aerobic processes.

Lade H, Kadam A, Paul D, Govindwar S - EXCLI J (2015)

Decolorization of azo dyes by bacterial consortium and formation of aromatic amines and TOC reduction under various experimental conditions
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4553892&req=5

T2: Decolorization of azo dyes by bacterial consortium and formation of aromatic amines and TOC reduction under various experimental conditions
Mentions: The results of the decolorization study showed that, 98-99 % decolorization of all the four dyes was observed within 30 h of incubation under microaerophilic conditions (Table 2(Tab. 2)). However, variation in decolorization time was observed for all the dyes viz. RB 5 (30 h), RO 16 (12 h), DR 78 (18 h) and DR 81 (24 h) and that may be due to the structural differences of azo dyes used (Moosvi et al., 2005[35]). It has been reported that the azo dyes with mono azo bond were more likely to be decolorized faster than those with diazo or triazo groups (Franciscon et al., 2009[15]). For this reason, RO 16 and DR 78, which are both monoazo dyes showed a short decolorization time (12 and 18 h, respectively) and the highly substituted diazo RB 5 and DR 81 showed longer decolorization times (30 and 24 h, respectively). It is suggested that, the azo dyes with a hydroxyl or amino groups were methoxy, sulfo or nitro groups (Nigam et al., 1996[37]). Hence, in the present study variation in decolorization time was observed for all the dyes as these have difference in number of azo bonds and its position. The complete decolorization of all the dyes at microaerophilic conditions suggest that this process favors the decolorization and which may be due to the involvement of reductive enzymes in initial break-down of azo dyes. It was reported that, reductive cleavage of azo bonds (–N=N–) by azoreductase normally occurs in absence or reduced levels of oxygen as in microaerophilic conditions (Chang et al., 2001[5]; Sheth and Dave, 2009[51]). In contrast to the complete decolorization of all the four dyes under microaerophilic condition, the reduced performance only up to 12 % for RB 5, 20 % for RO 16, 22 % for DR 78 and 21 % for DR 81 was achieved under aerobic conditions within the same time and even no complete decolorization was observed in 48 h (Table 2(Tab. 2)). A previous study on aerobic decolorization of azo dyes has also shown that this process is insufficient to completely degrade most of azo dyes (Ogugbue et al., 2012[38]).

Bottom Line: RB 5 (0.08 mM), RO 16 (0.06 mM), DR 78 (0.07 mM) and DR 81 (0.09 mM) resulted into the formation of aromatic amines.Additionally, 62-72 % reduction in total organic carbon content was observed in all the dyes decolorized broths under sequential microaerophilic/aerobic processes suggesting the efficacy of method in mineralization of dyes.Notable induction within the levels of azoreductase and NADH-DCIP reductase (97 and 229 % for RB 5, 55 and 160 % for RO 16, 63 and 196 % for DR 78, 108 and 258 % for DR 81) observed under sequential microaerophilic/aerobic processes suggested their critical involvements in the initial breakdown of azo bonds, whereas, a slight increase in the levels of laccase and veratryl alcohol oxidase confirmed subsequent oxidation of formed amines.

View Article: PubMed Central - PubMed

Affiliation: Department of Environmental Engineering, Konkuk University, Seoul-143-701, Korea.

ABSTRACT
Release of textile azo dyes to the environment is an issue of health concern while the use of microorganisms has proved to be the best option for remediation. Thus, in the present study, a bacterial consortium consisting of Providencia rettgeri strain HSL1 and Pseudomonas sp. SUK1 has been investigated for degradation and detoxification of structurally different azo dyes. The consortium showed 98-99 % decolorization of all the selected azo dyes viz. Reactive Black 5 (RB 5), Reactive Orange 16 (RO 16), Disperse Red 78 (DR 78) and Direct Red 81 (DR 81) within 12 to 30 h at 100 mg L(-1) concentration at 30 ± 0.2 °C under microaerophilic, sequential aerobic/microaerophilic and microaerophilic/aerobic processes. However, decolorization under microaerophilic conditions viz. RB 5 (0.26 mM), RO 16 (0.18 mM), DR 78 (0.20 mM) and DR 81 (0.23 mM) and sequential aerobic/microaerophilic processes viz. RB 5 (0.08 mM), RO 16 (0.06 mM), DR 78 (0.07 mM) and DR 81 (0.09 mM) resulted into the formation of aromatic amines. In distinction, sequential microaerophilic/ aerobic process doesn't show the formation of amines. Additionally, 62-72 % reduction in total organic carbon content was observed in all the dyes decolorized broths under sequential microaerophilic/aerobic processes suggesting the efficacy of method in mineralization of dyes. Notable induction within the levels of azoreductase and NADH-DCIP reductase (97 and 229 % for RB 5, 55 and 160 % for RO 16, 63 and 196 % for DR 78, 108 and 258 % for DR 81) observed under sequential microaerophilic/aerobic processes suggested their critical involvements in the initial breakdown of azo bonds, whereas, a slight increase in the levels of laccase and veratryl alcohol oxidase confirmed subsequent oxidation of formed amines. Also, the acute toxicity assay with Daphnia magna revealed the nontoxic nature of the dye-degraded metabolites under sequential microaerophilic/aerobic processes. As biodegradation under sequential microaerophilic/aerobic process completely detoxified all the selected textile azo dyes, further efforts should be made to implement such methods for large scale dye wastewater treatment technologies.

No MeSH data available.


Related in: MedlinePlus