<i>CgMRP1</i> improves ethanol fermentation performance of <i>Candida glycerinogenes</i> in undetoxified lignocellulosic hydrolysate

Cellulosic ethanol has become a hot spot in bioethanol research due to its advantages of low raw material price and abundant sources. However, inhibitory substances produced during lignocellulosic pretreatment inhibited yeast growth and fermentation. In this study, alkali pretreatment maximally disrupted the lignocellulose surface and yielded the highest concentration of fermentable sugars after enzymatic hydrolysis. <i>Candida glycerinogenes</i> is a multiresistant industrial yeast strain capable of fermenting undetoxified lignocellulosic hydrolysate. To further improve the tolerance of <i>C. glycerinogenes</i> to hydrolysate, recombinant strains with high tolerance to furfural, acetic acid and sodium chloride were constructed. Notably, the SOD and CAT activities of <i>CgMRP1</i> increased by 92.5% and 53.7%, respectively. The ROS content of <i>CgMRP1</i> reduced by 35.1% under furfural stress. In addition, the ethanol yield of <i>CgMRP1</i> increased by 13.8% and 20.5% under furfural and acetic acid stress, respectively. The fermentation of undetoxified lignocellulosic hydrolysate by <i>CgMRP1</i> resulted in an ethanol yield of 41.5 g/L, with a yield of 0.415 g/g glucose, and the ethanol conversion rate was about 81.2% of the theoretical conversion rate. This is the first report of ethanol production from <i>C. glycerinogenes</i> fermented undetoxified lignocellulosic hydrolysate, providing a new reference for cellulosic ethanol production.