Response surface optimization study on production of feed proteinase by Bacillus subtilis with composite inducers
The experiment aimed to establish a fermentation process for the production of neutral protease for feed using a composite inducer of lactose and isopropyl-β-D-thiogalactopyranoside(IPTG)as a substitute for IPTG in Bacillus subtilis.Through preliminary screening,the optimal inducer ratio was determined to be 0.025％o IPTG and 11.25 g/L lactose,resulting in a feed protease activity of 1 066.09 U/mL under the original process.After optimization of the fermentation process through single-factor experiments and response surface methodology,the best fermentation conditions were found to be an initial pH of 7.5,cultivation temperature of 36.5 ℃,inducer addition time of 3.2 hours,and fermentation time of 45 hours,yielding a neutral protease activity of 1 398.54 U/mL,which was 1.31 times higher than before optimization.The study indicates that the induction conditions with the composite inducer are more complex than those with IPTG alone,and it has potential industrial application value in the large-scale production of protease.It provides a foundation for the application of protease preparations as feed additives.
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