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To achieve the enzymatic synthesis of γ-glutamyl-S-allyl-L-cysteine (GSAC), γ-glutamyltranspeptidase from Bacillus licheniformis (BlGGT) was obtained through fermentation followed by ammonium sulfate precipitation, and its enzymatic properties were characterized. Using L-glutamine (L-Gln) as the γ-glutamyl donor and S-allyl-L-cysteine (SAC) as the acceptor, the reaction conditions for BlGGT-catalyzed synthesis of GSAC were optimized via single-factor and orthogonal experiments. The results showed that the optimal temperature for both transpeptidation and hydrolytic activities of BlGGT was 55 ℃. The optimal pH for the transpeptidation reaction was 9.0, whereas that for the hydrolysis reaction was 7.0. The metal ions Zn2+ significantly enhanced both the transpeptidation and hydrolytic activities of BlGGT (P<0.05), Mg2+ and Ca2+ also significantly promoted transpeptidation activity (P<0.05), while Cu2+, Fe3+ and Mn2+ exhibited significant inhibitory effects on both activities (P<0.05). The optimal reaction conditions for GSAC synthesis were determined as follows: BlGGT concentration of 1 mg/mL, molar ratio of L-Gln to SAC of 1:3, reaction temperature of 60 ℃, pH10.0, and reaction time of 6 h. Under these optimized conditions, the conversion yield of GSAC reached 19.10%±0.11%. The present study elucidated the enzymatic characteristics of BlGGT and established an efficient enzymatic process for GSAC synthesis, providing a theoretical foundation and technical support for the high-yield production of GSAC.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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