The bio-processing of soybean dregs by solid state fermentation using a poly γ-glutamic acid producing strain and its effect as feed additive

• Published in: Bioresource technology Vol. 291; p. 121841
• Main Authors: Jiang, Kang, Tang, Bao, Wang, Qian, Xu, Zongqi, Sun, Liang, Ma, Junjie, Li, Sha, Xu, Hong, Lei, Peng
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.11.2019
• Subjects: Animal Feed; Animals; Anti-nutritional factors; Bacillus amyloliquefaciens - metabolism; Bacillus amyloliquefaciens NX-2S; Behavior, Addictive; Behavior, Animal; Fermentation; Glycine max - metabolism; Poly-γ-glutamic acid; Polyglutamic Acid - analogs & derivatives; Polyglutamic Acid - biosynthesis; Rats; Solid state fermentation; Soybean dregs; Soybean dregs; Anti-nutritional factors; Poly-γ-glutamic acid; Solid state fermentation; Bacillus amyloliquefaciens NX-2S
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2019.121841

•Soybean dregs were first processed by a γ-PGA producing bacteria through SSF.•A maximum γ-PGA production of 65.79 g/kg was detected in single batch SSF.•After SSF, trypsin inhibitor, phytic acid, and tannin were reduced significantly.•Fermented soybean dregs significantly increased the average weight gain of rats. Soybean dregs are restricted as feed additives because they contain anti-nutrient factors. Herein, soybean dreg was bio-transformed by solid-state fermentation (SSF) using a poly γ-glutamic acid (γ-PGA) producing stain Bacillus amyloliquefaciens NX-2S. The maximum γ-PGA production of 65.79 g/kg was reached in a 5 L fermentation system while the conditions are 70% initial moisture of soybean dregs with addition of molasses meal, 12% inoculum size, 30 °C fermentation temperature, initial pH of 8, and 60 h fermentation time. Meanwhile, continuous batch fermentation was proved feasible. After SSF, the anti-nutritional factors such as trypsin inhibitor, phytic acid and tannin were reduced by 98.7%, 97.8%, and 63.2%, respectively. Compared with unfermented soybean dregs, adding fermented soybean dregs to feed increased the average weight gain of rats by 15.6% and reduced the ratio of feed to meat by 11.3%. Therefore, this study provided a feasible strategy for processing soybean dregs as feed additive.