两株素食者肠道菌产β-葡萄糖苷酶考察及产酶条件优化

采用对硝基苯基-β-D-葡萄糖苷法,与黑曲霉相比较考察素食者肠道菌LJ-G1、LJ-Q2产β-葡萄糖苷酶能力,再经单因素、响应面试验对菌种的产酶条件进行优化。结果表明:LJ-G1、LJ-Q2菌株均能产β-葡萄糖苷酶,且LJ-Q2产酶能力高于LJ-G1,与黑曲霉相比较,在发酵时间短于64 h时LJ-G1、LJ-Q2产酶能力高于黑曲霉;LJ-Q2菌种的最优产酶条件为:培养基p H 8.0、培养温度38℃、培养时间38 h。在最优条件下进行验证实验,酶活力达到1.70 IU/m L。加入大豆异黄酮原料进行发酵培养,得到游离大豆异黄酮转化率为39.4%。

Comparison of Two β-Glucosidase-Producing Strains from the Intestinal Tract of Vegetarians and Optimizaiton of Fermentation Conditions for β-Glucosidase Production

The β-glucosidase-producing capacity of strains LJ-G1 and LJ-Q2 isolated from the feces of vegetarians was
measured using 4-nitrophenol-β-D-glucoside (pNPG) as substrate and compared with that of Aspergillus niger. The
fermentation conditions for β-glucosidase production by the selected strain were optimized using combination of single factor
method and response surface methodology. The results showed that both intestinal strains were able to produce β-glucosidase,
and LJ-Q2 had higher β-glucosidase-producing capacity than LJ-G1. LJ-G1 and LJ-Q2 had higher β-glucosidase-producing
capacity than Aspergillus niger in 64 h of fermentation. The optimal fermentation conditions for β-glucosidase production
were determined as follows: culture medium pH, 8.0; temperature, 38 ℃; and time, 38 h. The experimental value of
β-glucosidase activity produced under the optimized conditions was 1.70 IU/mL. The fermentation process could convert
39.4% of soybean isoflavones into aglycones.