摘要
This study aimed to enhance the acidic activity of proteolytic enzymes produced by B.amyloliquefaciens BS5582 and reveal their application effect in soy sauce fermentation.Through ARTP mutagenesis,a B3 mutant strain with 277 U/mL activity under pH5.0 was obtained,which was 45.03%higher than that in BS5582.Moreover,the optimal pH of proteolytic enzymes from B3 mutant strain was decreased from pH7.5 to pH6.0 while it also displayed good stability under pH5.0-7.5.The proteolytic enzymes from B3 mutant strain also showed stronger high salinity tolerance ability since its half-life value(18.4 days)under 14%salinity was significantly longer than that in BS5582(14.4 days).The genome resequencing and RT-qPCR results showed that the up-regulated expression of acidic peptidase bpr gene was closely related to the enhancement of acidic enzymatic activity.After application in soy sauce fermentation,the concentrations of amino acid nitrogen and free amino acids in soy sauce with addition of B3 enzymes(0.85 g/100g and 2.77 g/100g)were 18.06%and 32.54%higher than those in blank,which were also better than those of BS5582 enzymes and commercial enzyme.Furthermore,the addition of B3 enzymes significantly improved the quantity and concentration of volatile flavor compounds with higher sensory evaluation scores for taste and aroma in soy sauce.The results obtained in this study showed that the proteolytic enzymes from B3 mutant strain had great potential application value in soy sauce fermentation.
基金
financially supported by the National Natural Science Foundation of China(No.32472294 and No.32272282).
