Simultaneous chromate reduction and azo dye decolourization by Brevibacterium casei: azo dye as electron donor for chromate reduction.
Chromate [Cr(VI)] and azo dyes are common pollutants which may co-exist in some industrial effluents. Hence studies of biological treatment of industrial wastewater should include investigation of the co-removal of these two pollutants. Brevibacterium casei, which can reduce Cr(VI) in the presence of the azo dye Acid Orange 7 (AO7) under nutrient-limiting condition, was isolated from a sewage sludge sample of a dyeing factory. Response surface methodology, which is commonly used to optimize growth conditions for food microorganisms to maximize product(s) yield, was used to determine the optimal conditions for chromate reduction and dye decolourization by B. casei. The optimal conditions were 0.24 g/L glucose, 3.0 g/L (NH(4))(2)SO(4) and 0.2 g/L peptone at pH 7 and 35 degrees C. The predicted maximum chromate reduction efficiencies and dye decolourization were 83.4+/-0.6 and 40.7+/-1.7%, respectively. A new mechanism was proposed for chromate reduction coupling with AO7 decolourization by B. casei. Under nutrient-limiting condition, AO7 was used as an e(-) donor by the reduction enzyme(s) of B. casei for the reduction of Cr(VI). The resulted Cr(III) then complexed with the oxidized AO7 to form a purple coloured intermediate.
Ng
Tsz Wai
TW
Department of Biology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China.
Cai
Qinhong
Q
Wong
Chong-Kim
CK
Chow
Alex T
AT
Wong
Po-Keung
PK
D001391:Azo Compounds / Q000378:metabolism*; D001951:Brevibacterium / Q000378:metabolism*; D002840:Chromates / Q000378:metabolism*; D003116:Color; D004396:Coloring Agents / Q000378:metabolism*; D003470:Culture Media; D004583:Electrons; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D013054:Spectrophotometry, Atomic
D001391:Azo Compounds; D002840:Chromates; D004396:Coloring Agents; D003470:Culture Media