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

Authors

  • Jingjing Li,

    1. Research and Development Center of Food Proteins, College of Light Industry and Food Science, South China University of Technology, Guangzhou, China
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  • Li Li

    Corresponding author
    • Research and Development Center of Food Proteins, College of Light Industry and Food Science, South China University of Technology, Guangzhou, China
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Correspondent: Fax: 86 20 87114263;

e-mail: lili@scut.edu.cn

Summary

Enzymatic hydrolysis of soybean protein isolate by the extracellular proteases from Actinomucor elegans and Rhizopus oligosporus at pH 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 pH 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 pH 5.5, there is a lower content of total free amino acids (39.20 mg per 100 mL; 62.68% hydrophobic amino acids) in the R. oligosporus protease hydrolysate. In conclusion, treatment with R. oligosporus protease at pH 5.5 achieves efficient degradation of soybean protein, suggesting a promising industrial process for making bitterless protein hydrolysates.

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