Abstract:To enhance the quality of garlic extract，increase the content of its active ingredient S-allyl-Lcysteine（SAC），and promote its industrial-scale production and application，this study isolated γ-glutamyl transpeptidase（GGT）-producing strains from natto，a traditional fermented soybean product sourced from various regions. Through initial screening based on colony morphology and subsequent re-screening based on enzyme activity，the strain BNP-BS001 with high GGT activity was obtained. Through a comprehensive array of morphological，physiological，and biochemical analyses and 16S rDNA sequencing，the strain BNP-BS001 was precisely characterized as Bacillus subtilis. Through single-factor and response surface optimization experiments，it was determined that the optimal fermentation process of the strain was a fermentation temperature of 37.0 ℃，an initial pH of 7.2，an inoculum size of 5.5%，and a fermentation duration of 48 hours. Under these conditions，the enzyme activity of GGT in the crude fermentation enzyme liquid reached a maximum of 231.42 U/L，which was 1.13 times increment compared to the pre-optimization level.Under the conditions of 50 ℃and pH9.0，the crude fermentation enzyme liquid was added to the garlic extract and enzymatically converted for three hours.γ-glutamyl-S-allyl-L-cysteine（GSAC）was completely transformed，and the S-allyl-L-cysteine content reached 0.821%，which was higher than that of the commercially available aged garlic extract and effectively shortened the processing time.