Screening and enzymatic characterization study of high-yield pprotease-producing bacterial strains derived from Shiping stinky tofu

Abstract

Objective: Obtaining hhigh-yield pprotease-pproducing bacterial resources through fermentation of advantageous protease-producing strains derived from Shiping stinky tofu. Methods: Single-factor and response surface experiments were used to optimize the culture medium and fermentation conditions. Using casein as the substrate, the effects of temperature, pH, metal ions and organic reagent on the protease activity and stability of strain JX-11 were investigated using enzymology techniques. Results: One strain of high-producing proteinase-secreting bacteria, JX-11, was isolated from Shiping stinky tofu, identified as Chryseobacterium pennipullorum. The optimal conditions for protease production by JX-11 strain were found to be temperature at 23.0 ℃, glucose content at 6.7 g/L, peptone content at 15.0 g/L, pH 6.4. Under these conditions, the protease activity was (39.16±3.24) U/mL. The optimal temperature for extracellular protease of JX-11 strain was 30 ℃, and it had good stability in the range of 10～40 ℃. The optimal pH was 7.0, and it had good stability in the range of pH 6.0～9.0. Mn2+ significantly increased the activity of JX-11 protease. The relative activity was increased by 4.33 times compared with the blank group. Zn2+, Cu2+, and K+ all inhibited the enzyme activity, Na+, Mg2+, and Ca2+ had no significant effect. Glycerol can promote the activity of the enzyme, but ethanol and acetone have little effect on it. Tween 80, acetic acid, methanol and EDTA inhibited the activity of the enzyme, among which EDTA hadd the most obvious inhibition, which further proved that the enzyme was a metalloprotease. Conclusion: A high-producing protease-secreting bacterial strain is obtained from Shiping stinky tofu, which has good application prospects.

Keywords

• chryseobacterium pennipullorum
• protease
• screening and identification
• enzymatic properties