Quality improvement of soybean meal by yeast fermentation based on the degradation of anti-nutritional factors and accumulation of beneficial metabolites

Background Soybean meal (SBM) is the main protein source for animal diets but its anti-nutritional constituents affect animal growth and immunity. The yeast culture of soybean meal (SBM-YC) that fermented with yeast and hydrolyzed by protease simultaneously could reduce anti-nutritional factors effectively and accumulate beneficial metabolites.Results The crude protein and acid-soluble protein content of SBM-YC reached 542.5 g kg(-1) and 117.2 g kg(-1), respectively, and the essential amino acid content increased by 17.9%. Raffinose and stachyose decreased over 95.0%, and the organic acid content such as acetic acid, butyric acid, citric acid, lactic acid, succinic acid, and propionic acid produced by fermentation reached 6.1, 3.8, 3.6, 2.5, 1.2, and 0.4 g kg(-1), respectively. As biomarkers of yeast culture, nucleosides and their precursors reached 1.7 g kg(-1); in particular, the inosine content increased from 0 to 0.3 g kg(-1). The total antioxidant capacity, 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) free radical activity, metal chelating ability, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging ability were increased by 50.3%, 46.1%, 43.9%, and 20.6%, respectively.Conclusion This study established a diversified evaluation index, which could lay the foundations for the production and quality control of SBM-YC in the future. (c) 2023 Society of Chemical Industry.

Automated summary

The yeast culture of soybean meal (SBM-YC), produced by yeast fermentation and protease hydrolysis, reduces anti-nutritional factors, increases protein and essential amino acid content, and accumulates beneficial organic acids and nucleosides, resulting in improved antioxidant capacity.