Abstract:

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.

Key words: vegetarians, intestinal bacteria, β-glucosidase, fermentation conditions for β-glucosidase production