Rapid alcoholic fermentation of Candida glycerinogenes under aerobic conditions

The toxicity of lignocellulosic hydrolysate has long plagued the alcoholic fermentation industry, whereas elevating dissolved oxygen concentrations can effectively enhance microbial tolerance and fermentation efficiency. This study further elucidates the rapid sugar metabolism mechanism of Candida glycerinogenes under aerobic conditions by examining its carbon flux allocation and sugar metabolic rates. C. glycerinogenes has an excellent performance on glycolytic rate and ethanol productivity compared to Saccharomyces cerevisiae under aerobic conditions. Unlike S. cerevisiae W303, C. glycerinogenes had an increasing NADH/NAD⁺ ratio and maintained high activities of glycolytic enzymes at high ATP levels. The maximum inhibitory effect of ATP on the relative activities of hexokinase (HXK), phosphofructose kinase (PFK), and pyruvate kinase (PYK) in S. cerevisiae W303 was 2.69, 1.35, and 1.41 fold that of C. glycerinogenes, respectively. Overexpression of PFK1 from C. glycerinogenes in S. cerevisiae W303 could increase the glycolytic rate, increasing the maximum glucose consumption rate by 14.48%. The high activities of glycolytic enzymes and their insensitivity to ATP inhibition may be key and prerequisite factors for the rapid fermentation of C. glycerinogenes. These results help understand the rapid fermentation from the perspectives of NAD(H) and ATP regulation, and provide new insights into the production of ethanol and other glycolytic products.