Enhancing erythritol production from crude glycerol in a wild-type by metabolic engineering.

Erythritol is a zero-calorie sweetener that is widely used in the food, pharmaceutical, and medical industries. Crude glycerol is the main by-product of biodiesel, and the effective utilization of crude glycerol will help to improve biodiesel viability. Previous studies on the production of erythritol from using crude glycerol as a carbon source have focused on optimizing the fermentation process of the mutant Wratislavia K1, while metabolic engineering has not been successfully applied. To this end, we engineered the yeast to increase the productivity of this strain. Wild strains tolerant to high concentrations of crude glycerol were screened and identified. A series of rational metabolic approaches were employed to improve erythritol production. Among them, the engineered strain Y-04, obtained by tandem overexpression of and , significantly increased glycerol assimilation by 33.3%, which was consistent with the results of RT-qPCR analysis. The effects of tandem overexpression of , , and on erythritol synthesis were also evaluated. The best results were obtained using a mutant that overexpressed , and and knocked out . The final Y-11 strain produced 150 g/l erythritol in a 5-L bioreactor with a yield and productivity of 0.62 g/g and 1.25 g/l/h, respectively. To the best of our knowledge, this is the highest erythritol yield and productivity from crude glycerol ever reported in . This work demonstrated that overexpression of , and and knockdown of could be used to improve crude glycerol utilization and erythritol synthesis in . The process parameters such as erythritol yield and productivity were significantly elevated, which is valuable for industrial applications. Crude glycerol, as a carbon source, could efficiently restrict the synthesis of by-products while enhancing the generation of erythritol, compared to glucose. This indicates considerable potential for synthesizing value-added products from crude glycerol by .