Figure 6.12: Fermentation (A) In lactic acid fermentation, NADH is used to reduce pyruvate to lactic acid, thus regenerating NAD+ to keep glycolysis operating. (B) In alcoholic fermentation, pyruvate is converted to acetaldehyde, and CO2 is released. NADH is used to reduce acetaldehyde to ethanol, again regenerating NAD+ for glycolysis.