Study and improvement of the conditions for production of a novel alkali stable catalase

摘要

Catalase(CAT)is an enzyme capable of catalyzing the conversion of H2O2 to O2 and H2O.It has recently acquired interest due to its attractive potential application in the textile industries.In a previous study,a bacterium with slight halophilic and alkaliphilic characteristics,Bacillus sp.F26,was isolated and found to produce high-level alkaline CAT.In the present study,the effects of cul ture conditions on the CAT production were investigated.The results showed that the highest ac tivity of CAT(13.9 U/mg protein)was obtained when glucose(15g/L)was used as carbon source.The utilization of the mixture of corn steep liquid and beef extract stimulated both bacterial growth and CAT synthesis.The highest biomass(4.5 g/L)and activity of CAT(16.5 U/mg protein)were found synchronously when 10 g/Lcorn steep liquid and 10g/L beef extract were used as nitrogen source.The addition of H2O2 as an oxidative stress was used to enhance CAT production in the flasks.It was found that the activity of CAT was increased by 51.3-22.8 U/mg protein compared with the control when 2 mmol/L H2O2 was added at later exponential phases(16 h),although the cell growth was significantly inhibited.Based on the above,an exponential H2O2 feed strategy was developed,in which the feed rate of H2O2 was controlled according to specific cell growth rate(u).In this way,the maximum CAT production(29.9 U/mL)was obtained,which was 92.8 and 20.7% higher than that in batch and constant rate fed-batch fermentation,respectively.