Glyceric acid (GA), an unfamiliar biotechnological product, is currently produced as a small by-product of
dihydroxyacetone production from glycerol by Gluconobacter oxydans. We developed a method for the efficient
biotechnological production of GA as a target compound for new surplus glycerol applications in the biodiesel
and oleochemical industries. We investigated the ability of 162 acetic acid bacterial strains to produce GA from
glycerol and found that the patterns of productivity and enantiomeric GA compositions obtained from several
strains differed significantly. The growth parameters of two different strain types, Gluconobacter frateurii
NBRC103465 and Acetobacter tropicalis NBRC16470, were optimized using a jar fermentor. G. frateurii accumulated
136.5 g/liter of GA with a 72% D-GA enantiomeric excess (ee) in the culture broth, whereas A. tropicalis
produced 101.8 g/liter of D-GA with a 99% ee. The 136.5 g/liter of glycerate in the culture broth was concentrated
to 236.5 g/liter by desalting electrodialysis during the 140-min operating time, and then, from 50 ml of the
concentrated solution, 9.35 g of GA calcium salt was obtained by crystallization. Gene disruption analysis using
G. oxydans IFO12528 revealed that the membrane-bound alcohol dehydrogenase (mADH)-encoding gene
(adhA) is required for GA production, and purified mADH from G. oxydans IFO12528 catalyzed the oxidation
of glycerol. These results strongly suggest that mADH is involved in GA production by acetic acid bacteria. We
propose that GA is potentially mass producible from glycerol feedstock by a biotechnological process.