Proteolysis characteristics of Actinomucor elegans and Rhizopus oligosporus extracellular proteases under acidic conditions.

Enzymatic hydrolysis of soybean protein isolate by the extracellular proteases from Actinomucor elegans and Rhizopus oligosporus at p H 3.0, 3.5, 5.0, 5.5 and 6.0 was investigated. The activity of the A. elegans protease is lower than that of R. oligosporus, but both proteases exhibit considerable degradation of soybean protein at p H 5.5 and 6.0. The water-soluble protein content and the degree of hydrolysis of the hydrolysates are increased significantly, and bitterness values are very low. Sodium dodecyl sulphate polyacrylamide gel electrophoresis ( SDS-PAGE) reveals that these proteases have different cutting sites on peptide polymers. At p H 5.5, there is a lower content of total free amino acids (39.20 mg per 100 m L; 62.68% hydrophobic amino acids) in the R. oligosporus protease hydrolysate. In conclusion, treatment with R. oligosporus protease at p H 5.5 achieves efficient degradation of soybean protein, suggesting a promising industrial process for making bitterless protein hydrolysates. [ABSTRACT FROM AUTHOR]