Solid-state fermentation through synthetic microbiome: An effective strategy for converting Chinese distillers' grains into functional protein feed

Abstract

Chinese distillers' grains (CDGs), a byproduct of liquor production, have low protein, high fiber, and elevated alcohol/lactic acid levels, limiting their use as animal feed. This study utilised a synthetic microbiome composed of Candida utilis (protein enhancement), Trichoderma viride (fiber reduction), Bacillus subtilis (detoxification), and Lactobacillus casei (functional enhancement) for solid-state fermentation. The results showed that crude protein content increased to 23.61 %, and true protein content to 20.45 %. Crude fiber, ethanol, lactic acid, and acetic acid contents decreased by 22.31 %, 77.25 %, 85.08 %, and 73.89 %, respectively. Amino acid content increased by 23.80 %, and flavour compounds rose by 140.76 %. Mycotoxins like aflatoxin B1 (AFB1) and ochratoxin A (OTA) were undetectable, while vomitoxin (DON) remained below EU limits. In vitro digestibility of dry matter increased by 98.36 %. Pilot-scale trials showed a 1.42-fold increase in crude protein and a 1.34-fold increase in true protein, contributing to more efficient CDG utilisation and reduced agricultural costs.