Oil and protein simultaneously extracted from soybean using crude enzyme produced by microbial fermentation

Enzyme-assisted aqueous extraction processing (EAEP) is an environmentally friendly alternative technology to hexane extraction of soybean oil，EAEP has significant challenges, however, that must be overcome before becoming practical: the high price of enzyme, activity is influenced significantly by conditions, which has discouraged industrial adoption of EAEP. In this study Bacillus subtilis was inoculated into the optimal medium and fermented for 42 h, it was found that the broth contained alkaline and neutral protease. Extruded full fat soybean flour was hydrolyzed by the crude enzyme obtained from fermentation liquid after condensation at alkaline protease activity of (2?000±200) U/mL, neutral protease of (1?500±200) U/mL. The total oil extraction yield reached the highest value of 94.2%, and 90.1% of total protein yield was obtained under conditions that were temperature 55℃, solid/liquid ratio 1:8 g/mL, the initial pH value 10, hydrolysis time 6?h. As compared to the commercial Alcalase protease , the total oil recovery enhanced by 1.9%, the protein recovery reduced by 2% with crude enzyme extraction，and the hydrolyzed protein molecular weights were smaller and distributed wider. The use of crude enzyme resulted in better oil quality as compared with solvent extraction, though no significant difference was observed between the treatments of crude enzyme and Alcalase protease .