Microbial diversity of soybean meal hydrolysate treated by keratinase

Abstract:

[Background] The nutritional value and flavor of feed ingredient was improved after fermentation and keratinase hydrolysis because microbiota compositions in the enzymolytic feed can be altered. In addition, enzymolytic soybean meal has significant improvements in growth performance and intestinal health. [Objective] Therefore, in this study, enzymolytic soybean meal (ESBM) was produced by fermentation and keratinase hydrolysis. The aim of this study was to explore the effect of two kinds of ESBM (keratinase hydrolyzed soybean meal (KHS) and keratinase hydrolyzed SBM with 30% inclusion of wheat bran (KHS-WB) on the microbiota diversity in the process of hydrolysis to drying. [Methods] First of all, the numbers of total bacteria, total mildew and yeast were measured by plate counting in laboratory. Additionally, Illumina MiSeq sequencing of 16S rRNA gene and ITS rDNA were employed to test the bacterial and fungal diversity dynamics of hydrolysis samples (0?36 h) in the pilot experiment. [Results] The plate counting result showed that the numbers of bacteria of two kinds of ESBM were 1 000?10 000 times higher than that of raw materials after treated with keratinase for 24 h. However, after drying, the counts of bacteria and fungi of ESBM were significantly decreased by 90%?99% than that of before drying. Moreover, the Illumina MiSeq sequencing results of 16S rRNA gene and ITS rDNA indicated that two kinds of ESBM had a similar alpha diversity index and microflora richness level. Additionally, the beta diversity of 16S rRNA sequencing result showed that Fructobacillus in KHS and Weissella in KHS-WB kept sustainable growth, occupied the privilege and became dominant bacterial genus (36 h), respectively. The results of ITS rDNA sequencing demonstrated that Aspergillus occupied the privilege in all genus of KHS while the diversity of dominant fungi was more abundant of KHS-WB in the process of hydrolysis. [Conclusion] Wheat bran as ESBM substrate can influence the microbiota diversity of ESBM, as well as the Weissella and yeast fungi will be the diversity of dominant microbes in the ESBM.