Optimization of Small Peptide Feed from Milk Thistle Residue by Synergistic Fermentation of Multiple Strains and Proteases

Abstract

In order to improve the utilization rate of the milk thistle residue, this study used the synergistic fermentation of multiple strains and proteases to increase the small peptide content of the fermented feed produced by the milk thistle residue. Taking the small peptide content of the milk thistle residue fermented feed as an indicator, the optimal fermentation process was obtained by single-factor optimization experiments and the response surface methodology. The optimal fermentation process was as follows: fermentation time of 7 days, inoculum size of 15%, inoculation ratio of aerobic strains: anaerobic strains = 1: 2, solid-state fermentation water content of 66%, fermentation temperature of 36℃, and amount of protease was 0.25% acid protease+0.25% bromelain. Under the above process, the small peptide content of the fermented feed from milk thistle residue was greatly improved to 57.86%. These results inferred that the added proteases were beneficial to the growth of fermentative microorganisms, the secretion of protease and the increase of the small peptide content.