Upgrading of by-product from beverage industry through solid-state fermentation with Candida utilis and Bacillus subtilis

Yellow wine lees (YWL) are the main co-products in yellow wine industry with unbalanced amino acid (AA) profiles. Solid-state fermentation was employed in this study to upgrade the YWL for ruminant animals. A 3 x 3 orthogonal design was conducted to optimize the fermentation condition for optimal crude protein (CP) yield as follows: ratio of water to total solid medium at 50 : 100 (v/w), temperature of 30 degrees C, and ratio of Candida utilis to Bacillus subtilis at 2 : 1. The contents of CP, peptides and AA of fermented products were 14 center dot 5, 40 center dot 9 and 26 center dot 1% higher than those of the unfermented respectively. In particular, the essential AA were highly improved, especially for lysine and methionine. The fermentation increased the in vitro microbial protein synthesis with higher CP digestibility and dramatically enhanced the ability of scavenging free radicals of the YWL. It is concluded that the microbial pretreatment can greatly improve the nutritional value of YWL, making these materials more suitable as feeds for animals, including ruminants.