Biodegradation of methyl red by Bacillus sp. strain UN2: decolorization capacity, metabolites characterization, and enzyme analysis.
Azo dyes are recalcitrant and refractory pollutants that constitute a significant menace to the environment. The present study is focused on exploring the capability of Bacillus sp. strain UN2 for application in methyl red (MR) degradation. Effects of physicochemical parameters (pH of medium, temperature, initial concentration of dye, and composition of the medium) were studied in detail. The suitable pH and temperature range for MR degradation by strain UN2 were respectively 7.0-9.0 and 30-40 °C, and the optimal pH value and temperature were respectively 8.0 and 35 °C. Mg(2+) and Mn(2+) (1 mM) were found to significantly accelerate the MR removal rate, while the enhancement by either Fe(3+) or Fe(2+) was slight. Under the optimal degradation conditions, strain UN2 exhibited greater than 98 % degradation of the toxic azo dye MR (100 ppm) within 30 min. Analysis of samples from decolorized culture flasks confirmed biodegradation of MR into two prime metabolites: N,N'dimethyl-p-phenyle-nediamine and 2-aminobenzoic acid. A study of the enzymes responsible for the biodegradation of MR, in the control and cells obtained during (10 min) and after (30 min) degradation, showed a significant increase in the activities of azoreductase, laccase, and NADH-DCIP reductase. Furthermore, a phytotoxicity analysis demonstrated that the germination inhibition was almost eliminated for both the plants Triticum aestivum and Sorghum bicolor by MR metabolites at 100 mg/L concentration, yet the germination inhibition of parent dye was significant. Consequently, the high efficiency of MR degradation enables this strain to be a potential candidate for bioremediation of wastewater containing MR.
College of Life Sciences, Zhejiang University, 310058, Hangzhou, Zhejiang, People's Republic of China.
Ming
M
Zhao
Peng-Fei
PF
Sun
Lin-Na
LN
Du
Guan
G
Wang
Xiao-Ming
XM
Jia
Yu-Hua
YH
Zhao
D001391:Azo Compounds / Q000032:analysis / Q000378:metabolism*; D001407:Bacillus / Q000201:enzymology / Q000378:metabolism*; D001673:Biodegradation, Environmental; D004396:Coloring Agents / Q000032:analysis / Q000378:metabolism*; D007220:Industrial Waste / Q000032:analysis; D042845:Laccase / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D009601:Nitroreductases; D011808:Quinone Reductases / Q000378:metabolism; D013784:Textiles; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater / Q000737:chemistry / Q000382:microbiology; D062367:ortho-Aminobenzoates / Q000378:metabolism
D001391:Azo Compounds; D004396:Coloring Agents; D007220:Industrial Waste; D042845:Laccase; D009247:NADH, NADPH Oxidoreductases; D009601:Nitroreductases; D011808:Quinone Reductases; D062065:Wastewater; D062367:ortho-Aminobenzoates; C031385:anthranilic acid; C008492:methyl red; C033633:dichlorophenolindophenol reductase; C021106:azoreductase