Quality control and law exploration of microbial oil production from spent grains fermented by Wickerhamomyces anomalus CY2.

Microbial oils are gaining attention as a promising raw material for biodiesel production. However, the high cost of microbial culture media and the elevated cold filter plugging point of the resulting biodiesel hinder their conversion. This study focused on fermenting SGs with added metal ions to regulate microbial oil saturation and enhance biodiesel quality. We investigated the relationship between sugar metabolism and lipid synthesis in the CY2 strain fermentation of SGs, aiming to provide insights into metabolic regulation for the industrial production of microbial oils. The results indicated that the addition of 50 mg/L FeCl•6HO to the lipid-producing medium for the CY2 strain significantly enhanced the content of unsaturated fatty acids without compromising the yield of microbial oils. This modification effectively reduced the cold filter plugging point of biodiesel, thereby improving its anti-freezing performance. In the analysis of material metabolism during the fermentation of SGs by the CY2 strain, it was observed that amylase and cellulase activities increased from 24 h to 60 h. The sugar content initially decreased, reaching its lowest point at 36 h, before gradually rising again. Within the first 48 h of fermentation, sugar catabolism in the CY2 strain surpassed lipid synthesis metabolism, leading to rapid microbial growth and reproduction. Subsequently, microbial growth plateaued, with excess carbon sources converted into triglycerides. This study produced high-quality biodiesel from low-cost SGs using Wickerhamomyces anomalus and provided a theoretical basis for metabolic regulation in microbial oil production and industrial fermentation, highlighting significant economic and environmental benefits.