Abstract
Bacillus velezensis is widely used for agricultural biocontrol, due to its ability to enhance plant growth while suppressing the growth of microbial pathogens. However, there are few reports on its application in fermented feed. Here, a two-stage solid-state fermentation process using Bacillus velezensis followed by Lactobacillus plantarum was developed to degrade antinutritional factors (ANFs) and improve soybean meal (SBM) nutrition for animal feed. The process was evaluated for performance in degrading SBM antinutritional factors, dynamic changes in physicochemical characteristics, microorganisms and metabolites. After two-stage fermentation, degradation rates of glycinin and β-conglycinin contents reached 78.60% and 72.89%, respectively. The pH of fermented SBM (FSBM) decreased to 4.78 ± 0.04 and lactic acid content reached 183.38 ± 4.86 mmol/kg. NSP-degrading enzymes (Non-starch polysaccharide, NSPases) and protease were detected from the fermented product, which caused the changed microstructure of SBM. Compared to uninoculated SBM, FSBM exhibited increased proportions of crude protein (51.97 ± 0.44% vs. 47.28 ± 0.34%), Ca, total phosphorus (P), and trichloroacetic acid-soluble protein (11.79 ± 0.13% vs. 5.07 ± 0.06%). Additionally, cellulose and hemicellulose proportions declined by 22.10% and 39.15%, respectively. Total amino acid content increased by 5.05%, while the difference of AA content between the 24 h, 48 h and 72 h of fermentation was not significant (P > 0.05). Furthermore, FSBM also showed antibacterial activity against Staphylococcus aureus and Escherichia coli. These results demonstrated that two-stage SBM fermentation process based on Bacillus velezensis 157 and Lactobacillus plantarum BLCC2-0015 is an effective approach to reduce ANFs content and improve the quality of SBM feed.
Highlights
Soybean meal (SBM) is the most common source of plant protein used by the food and feed industries
Microorganisms, pH, antimicrobial activity and lactic acid concentration during solid-state fermentation (SSF) Two-stage fermentation based on activities of B. velezensis 157 and L. plantarum BLCC2-0015 significantly altered microorganisms, pH and lactic acid concentration of SBM (Fig. 1a)
The hydrolytic effects of the proteases secreted by B. velezensis 157 were able to decompose antigenic protein in fermented SBM (FSBM) during the first fermentation
Summary
Soybean meal (SBM) is the most common source of plant protein used by the food and feed industries. Phylogenetic analysis has revealed that Bacillus velezensis, Bacillus amyloliquefaciens, and Bacillus siamensis were clustered tightly together to form the “operational group Bacillus amyloliquefaciens” (Fan et al 2017) This classification scheme is interesting in that it reflects the characteristics of B. velezensis that make this species widely applicable to biocontrol applications (Ye et al 2018), such as commercial biofertilizers and biopesticides that currently employ strains SQR9 (Zhang et al 2015), 9912D (Pan et al 2017), LM2303 (Chen et al 2018c), and FZB42 (Fan et al 2018). Only a few studies have already been reported for the processing of agro-industrial waste using pairs of organisms to optimize the quality of fermented feed, such as Bacillus subtilis and Enterococcus faecium (Shi et al 2017a), Bacillus subtilis and Saccharomyces cerevisiae (Chen et al 2009), and Bacillus subtilis and Bacillus coagulans (Yeh et al 2018). B. velezensis can be recommended for the QPS list with the qualification ‘absence of toxigenic potential and absence of aminoglycoside production ability, which has a broad application prospect in feed additive and fermentation feed industry (Koutsoumanis et al 2020a, b)
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