A comparative study on enzyme production ability of microorganism producing γ-aminobutyric acid in processing of Sojae Semen Praeparatum at different pH and temperatures / 中草药

ABSTRACT

Objective: To lay a foundation for elucidating the mechanism of microbial regulation of γ-amino butyric acid (GABA) formation in the processing of Sojae Semen Praeparatum. Methods: The ability of glutamic acid decarboxylase and protease (neutral protease, alkaline protease and acid protease) production of Bacillus subtilis, Enterococcus avium, Enterococcus faecium, Bacillus amyloliquefaciens, Aspergillus niger, Aspergillus flavus, Aspergillus tamarii, Penicillium citrinum, Cladosporium tenuissimum, Phanerochaete sordida, Rhizopus oryzae, Sporidiobolus salmonicolor in different pH and temperature conditions were determined by Berthelot colorimetry and Folin phenol method. Results: The GAD and protease activities of the twelve strains were stronger at pH 5-7 and temperature 28-37 ℃. The highest GAD enzyme activity from A. flavus was 41.97 U/h, the optimum pH was 7 and the temperature was 28 ℃, followed by S. salmonicolor, A. niger, R. oryzae, and B. subtilis, respectively. The enzyme activities were 29.04, 25.78, 22.42 and 19.43 U/h. The highest neutral protease activity of B. subtilis was 24.80 U/mL, the optimum pH was 7 and the temperature was 37 ℃, followed by B. amyloliquefaciens, R. oryzae and E. avium. The enzyme activities were 16.86, 12.51 and 9.18 U/mL. The highest alkaline protease activity of B. amyloliquefaciens was 13.29 U/mL, the optimum pH was 7 and the temperature was 34 ℃, followed by B. subtilis and R. oryzae. The enzyme activities were 8.86 and 6.20 U/mL, respectively. The ability of 12 kinds of microorganisms to produce acid protease was generally poor. Conclusion: The optimal pH and temperature of the 12 kinds of microorganisms selected for this experiment are basically consistent with the natural processing of Sojae Semen Praeparatum. Among them, fungi have stronger GAD production capacity and bacteria have stronger neutral protease production capacity. The high GABA concentration of Sojae Semen Praeparatum is caused by the joint action of multiple strains.