Catalyzes the NAD-dependent oxidation of glycerol to dihydroxyacetone (glycerone). Allows microorganisms to utilize glycerol as a source of carbon under anaerobic conditions. Is also able to use various diols as substrates, such as propan-1,2-diol, butan-2,3-diol, ethan-1,2-diol, and 3-mercapto-1,2-dihydroxypropane. glycerol + NAD(+) = dihydroxyacetone + H(+) + NADH Binds 1 zinc ion per subunit. Optimum pH is 6.0-8.5. Polyol metabolism; glycerol fermentation; glycerone phosphate from glycerol (oxidative route): step 1/2. Homooctamer. Consists of two domains that are separated by a deep cleft, in which the Zn(2+) ion is bound. Belongs to the iron-containing alcohol dehydrogenase family.