Abstract:[Objective] The purpose was to study azo reduction activity in the strain Aeromonas hydrophila HS01 under anaerobic conditions. [Methods] We established the anaerobic system of HS01/electron donor/azo dye to investigate the ability of strain HS01 to obtain energy for growth by coupling the oxidation of electron donors to azo reduction, and further explore the enhanced azo microbial reduction by the presence of Fe(III) oxides. [Results] Within 30 h, HS01 could reduce 0.45 mmol/L orange I at the expense of 4.35 mmol/L glucose, and the active cells increased by 27 times in the treatments of HS01/glucose/orange I. The decolorization rate of orange I reached 87%, 85%, 88%, and 90%, respectively, when citrate, glycerol, sucrose or glucose served as the electron donor. It showed different decolorization rate by pH of 5?10 and 0.5?5.0 mmol/L of initial concentrations of orange I. In the system of HS01/glucose/orange with α-FeOOH, decolorization rate increased from 90% to 95%. [Conclusion] HS01 was capable of anaerobic respiration on orange I as the sole terminal electron acceptor with glucose as the electron donor. The decolorization rate depended on the types of electron donor, pH and initial concentrations of azo: citrate, glycerol, sucrose or glucose could serve as an effective electron donor for dissimilatory azo reduction, whereas formate, acetate, propionate, lactate and ethanol do the opposite; pH of 6.0?8.0 was optimum for azo reduction by HS01. Dissimilatory Fe(III) reduction and azo reduction by strain HS01 occurred simultaneously, and the presence of Fe(III) oxides would enhance orange I decolorization.
