Evaluation of a phenolic-tolerant Wickerhamomyces anomalus strain for efficient ethanol production based on omics analysis

Lignocellulosic biomass is a highly economically viable substrate for ethanol fermentation, but the presence of phenolic compounds (PCs) in lignocellulosic hydrolysates severely hinders the growth of ethanologenic strains. This study aims to investigate the ethanol fermentation capabilities and PC tolerance of the newly isolated Wickerhamomyces anomalus CAP5. The strain demonstrated remarkable ethanol production, achieving 87.1 g/L with a yield of 0.47 g/g, exceeding 90 % of the theoretical maximum. To elucidate the mechanisms responsible for this high ethanol yield, comprehensive genome and transcriptome analyses were performed. These analyses identified key metabolic pathways, including acetate reabsorption and an incomplete glycerol synthesis pathway, as crucial factors contributing to the strain's superior performance. Moreover, W. anomalus CAP5 demonstrated notable resistance to PCs, particularly phenolic acids. In fermenting with coffee husk hydrolysate (CHH), which is rich in PCs, W. anomalus CAP5 achieved noteworthy ethanol production of 60.5 g/L, marking a record for ethanol production from CHH. Hence, W. anomalus CAP5 emerges as a promising strain for effective ethanol production from lignocellulosic hydrolysates enriched with PCs.