Production of protease from Bacillus subtilis TISTR 25 by fermentation process with microfiltration

Abstract

Nowadays, the major applications of proteases produced by Bacillus species are found in brewing, detergent, food and leather industries. Proteases account for nearly 60% of the total enzyme sales in which two-thirds of them were produced commercially by microbial. The medium for effective protease production comprises enzymatically hydrolyze starch hydrolysed protein, and mineral sources. From the studies of batch fermentation at 37 ℃ with maximum aeration rate, the optimum pH and optimum concentration of initial glucose from starch hydrolyzation are 7.0 and 1.8 g/l, respectively. Bacillus subtilis TISTR 25, with maximum specific growth rate of 0.52 hr-1, performs the mixed growth association with protease. The protease productivity in the continuous fermentation coupling with microfiltration is lower than that of the batch fermentation because the high dilution rate cannot be achieved. Moreover, the retained cells are too old to produce protease. The twice cell bleeding continuous fermentation coupling with microfiltration, which partially eliminates the age problem, can improve 1.53-fold protease productivity comparing to batch fermentation.