Novel fermentation strategy utilizing a probiotic complex to improve the feeding value of distillers’ grains

Distillers’ grain (DG), an economical industrial by-product, contains high levels of crude fiber and harmful constituents, which significantly reduce its feeding value and contaminate the environment. This study aimed to evaluate the dynamic changes resulting from using a probiotic complex and cellulase preparation during two-stage solid-state fermentation to improve the nutritional value of DGs. Single-strain fermentation demonstrated that Bacillus subtilis RLI2019, Lactobacillus plantarum DPH, or Saccharomyces cerevisiae E9 increased the beneficial constituents of a mixture of DGs (73 %) and millet bran (20 %). Two-stage fermentation of the DG mixture was carried out with the aforementioned strains and cellulase preparation. After fermenting with the probiotic complex or cellulase preparation for 180 h, the crude protein content, acid-soluble protein content, the abundance of lactic acid bacteria, and beneficial compounds content were significantly increased. The cellulose content, abundance of acetic acid bacteria, and abundance of pathogenic Salmonella , Pantoea , and Escherichia were reduced, along with crystallinity and the degradation of chemical bonds in cellulose. The use of the probiotic complex improved the antioxidant capacity more effectively and reduced the content of anti-nutritional factors and deoxynivalenol compared with the cellulase preparation. During probiotic complex fermentation, the antioxidant capacity significantly improved after 120 h, with a robust reduction in anti-nutritional factors and deoxynivalenol. Overall, the findings showed that the evaluated probiotic complex could replace cellulase preparation in the two-stage solid-state fermentation of the DG mixture, offering novel insight into the efficient utilization of industrial by-products rich in cellulose. • Both probiotic complex and cellulase preparation altered fiber content and structure. • Probiotic complex replaced cellulase preparation for distiller’s grains’ fermentation. • The probiotic complex effectively improved feeding value of distillers’ grains. • The probiotic complex increased lactic acid bacteria abundance more effectively.