Efficient ethanol production from non-detoxified sugarcane molasses by an engineered Wickerhamomyces anomalus

Sugarcane molasses (SCM) is an abundant and inexpensive feedstock for bioethanol production, yet its direct use remains hindered by metal ion toxicity and osmotic stress. In this study, the non-conventional yeast Wickerhamomyces anomalus CAP5 was evaluated for ethanol fermentation from non-detoxified SCM. The strain sustained ethanol production under 60 g/L K+ or 40 g/L Ca2+/Mg2+ stress, demonstrating remarkable robustness in metal ion–rich environments. However, inefficient sucrose utilization, particularly in mixed-sugar conditions, constrained its fermentative efficiency. To address this, the S. cerevisiae invertase-encoding gene (suc2) was stably integrated, generating the recombinant strain CAP5/suc2. In batch fermentation with 25 °Brix SCM, CAP5/suc2 achieved complete sucrose hydrolysis within 24 h and produced 82.65 g/L ethanol with a yield of 0.45 g/g, representing 29.40 % and 7.14 % improvements over the wild-type strain and performance comparable to several industrial S. cerevisiae strains using detoxified SCM. These findings highlight engineered W. anomalus CAP5 as a promising candidate for industrial ethanol production from non-detoxified SCM, with potential applicability to both normal-gravity and high-gravity fermentation.