[Thermo-alkali-stable catalase from Thermoascus aurantiacus and its potential use in textile bleaching process]

The effect of growth and fermentation conditions on the production of catalase by T. aurantiacus WSH 03-01 was investigated in shaking flasks. Catalase activity reached 1594 u/mL when the culture was grown on a complex carbon source containing 20 g/L dextrin and 1% (V/V) ethanol, which was 23% higher than the sum produced on 20 g/L dextrin and 1% (V/V) ethanol, respectively. It was concluded that dextrin might act as a major carbon source in the complex, while ethanol was rather a stimulator than a carbon source. The stimulation effect of ethanol on catalase production was postulated to be two aspects; catalase-dependent alcohol metabolism is activated by acute alcohol, thus more catalase need to be synthesized for that use, named direct induction. As for indirect induction, which may result from little amount of H2O2 generation in process of NADH regeneration in respiratory chain. Peptone was shown to be a favorable nitrogen source for catalase production and its optimum concentration was found to be 10 g/L. Catalase production by T. aurantiacus WSH 03-01 was further improved by optimizing the initial pH, volume of medium in flasks as well as the concentration of external H2O2. Under the optimum culture conditions, the activity of catalase reached 2762 u/mL, which was nearly 6.8 times higher than that of the initiate conditions. Furthermore, the potential application of this novel catalase in the treatment of textile bleaching effluents was evaluated. Thermo-and alkaline stability of this catalase was compared with the commercial available catalases produced from bovine and Aspergillus niger. The crude enzyme from T. aurantiacus WSH 03-01 showed stronger stabilities at (70 degrees C, 80 degrees C, 90 degrees C) and (pH 9.0, pH 10.0, pH 11.0) than the other two types of catalases, indicating a great application potential in the clean production process of textile industry.