Quality evaluation of compound feed fermented by Bacillus subtilis
The experiment aimed to study the product quality of the Bacillus subtilis-fermented compound feed.The trial optimized the fermentation conditions by examining the effects of wheat bran addition,the ratio of auxiliary materials(addition of garlic peel and ginkgo leaf),and fermentation time on protease activity,and comprehensively evaluated the nutritional value and quality of the fermented feed by detecting the number of live bacteria and pH value before and after fermentation,as well as the content of conventional nutrients,peptides,soluble protein,and free amino acids,and the degree of protein hydrolysis during the fermentation process.The results showed that based on protease activity as an indicator,the optimal fermentation conditions were determined through single-factor and orthogonal tests to be 2％wheat bran,2.5％garlic peel+2.5％ginkgo leaf,and a fermentation time of 72 hours.Under these conditions,the protease activity was 342.36 U/g.Bacillus subtilis UL-191 grew well on the substrate,with the number of live bacteria reaching 3.5×1014 CFU/g.There were no significant changes in moisture and crude ash content before and after fermentation,while the content of crude protein and crude fat increased significantly,with large molecular proteins being degraded into proteins of smaller molecular weights.The degree of protein hydrolysis,peptide content,and free amino acid content all showed an upward trend with the extension of fermentation time.At 72 hours of fermentation,the degree of protein hydrolysis reached 25％,and the contents of peptides and free amino acids reached 182.9 and 1 006.4 pg/g,respectively.The study indicates that the quality of the experimentally prepared fermented compound feed is high and has certain market application prospects.
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