RESUMO
The production of α-galactosidase from the wild fungal strain Aspergillus foetidus MTCC 6322 using solid state fermentation (SSF), its characterization, and its efficacy in the hydrolysis of soymilk using response surface methodology were studied. The optimum conditions for production of α-galactosidase by SSF were: wheat bran (10 g), moisture content (64%), inoculum volume (1.0 mL; 6 × 107 spores/mL) with a yield of 4.1 × 103 units per gram dry substrate (U/gds) at 96 h. The enzyme showed optimum activity at pH 6.0, temperature 40°C, pH stability between 5.0-8.0, and temperature stability between 30-40°C. The enzyme was stable in the presence of trypsin, lipase, and collagenase and it showed susceptibility of the substrates such as raffinose, melibiose, guar gum and soymilk to hydrolysis in varying degrees. The optimized conditions for soymilk hydrolysis were: soymilk (10 mL) from defatted soybean meal (1.5%), α-galactosidase (0.15 UmL-1) at 30°C, pH 6.0 and duration of 1 h.