FIG. 1.

Schematic pathways of glucose and acetate cometabolism in l-LDH-deficient L. lactis. The proposed pathway of acetate conversion to ethanol and its coupling to glycolysis for cofactor regeneration is highlighted (grey area). Reactions or pathways producing NADH are denoted by large black arrows, those that are NADH independent are denoted by thin black arrows, and those producing NAD⁺ are denoted by large white arrows. The fate of the label derived from [2-¹³C]glucose and [2-¹³C]acetate (shaded region) is shown. ACK, acetate kinase; ADC, α-acetolactate decarboxylase; ADH, acetaldehyde/alcohol dehydrogenase; A/DR, α-acetolactate/diacetyl reductase; NOX, NADH oxidase; ODC, oxidative decarboxylation (chemical reaction); PDHC, pyruvate dehydrogenase complex; PFL, pyruvate/formate lyase; PTA, phosphotransacetylase; ?, unknown enzyme(s) involved in residual lactate production.