Optimization Of Culture Condition For Catalase Production By Bacillus Subtilis WSHDZ-01

Catalase can decompose H2O2 into H2O and O2 effectively. Physiologically it acts as a regulator of H2O2 levels in organelles and protect organism from the damage of reactive oxygen species. Catalases from various sources are utilized in several applications, such as diseases diagnosis and removal of hydrogen peroxide in food sterilization. Catalase is used in removal of hydrogen peroxide in the textile pretreatment as a substitute for high-temperature water washing and using chemical reducing agents.In our previous study, the biomass of Bacillus subtilis WSHDZ-01 was only 1.25 g/L. The production of catalase was strongly affected by the low biomass concentration. For industrial production of catalase, the biomass concentration should be improved at first. In this study, the nutrition condition and the environmental conditions for the cultivation of Bacillus subtilis WSHDZ-01 for the production of catalase were investigated.1.The effect of nutrition condition on catalase production by Bacillus subtilis WSHDZ-01 was investigated. It was found that sodium nitrate was the optimum nitrogen source. The effect of adding various organic nitrogen sources on cell growth was further studied, the result indicated that appropriate addition of malt extract could both greatly increase the biomass and shorten fermentation time. Comparison with that before optimization, the biomass reached 6g/L, the catalase activity was 11000 U/mL, fermentation time was shortened nearly 60% and the productivity of catalase increased 3 times.2.According to the fermentation experiments in 3 liters fermentor, it was found the agitator speed was not the vital factor for catalase production. The better culture condition was as follows: the initial sugar concentration at 20 g/L, the agitator speed at 400 rpm, aeration rate at 1.0 vvm.3.To enhance the yield of catalase, the kinetic parameters of batch fermentation at different temperatures ranging from 30 to 40℃were investigated. It was found that at the lower temperature such as 32℃, the production capability was elevated and rate of catalase was promoted. Based on the kinetic parameter analysis, a multi-staged temperature controlling strategy was proposed, in which temperature was controlled at 40℃in the first 10 h, then shifted to 35℃during 10-20 h, and finally shifted to 32℃afterwards. It was experimentally verified. By using this strategy, the maximum catalase activity was 20896 U/mL and increased by 47% by comparison with that of constant temperature 32℃.4.On the base of theory calculation, the culture conditions in 30 L fermentor are as follows: agitator speed was at 313 rpm and aeration rate at 0.56 vvm. The experimental results show that agitator speed of 300 rpm, aeration rate of 0.6 vvm, back pressure at 0.02 MPa and content volume above 60% are optimal culture conditions for catalase production. The results match the ones in 3 liters fermentor. 5.Based on the fermentation process analysis, it was found that the maximum extracelluar catalase activity reached the peak point when the total catalase production decreased. Considering the complexity of extraction of intracellular catalase, it is suggested to end fermentation process when the extracelluar catalase production reaches the peak point.