A slow feed batch fermentation is described for the production of glycerol from sugar. The conversion efficiency was approximately 1 mole of glycerol produced per mole of glucose utilized after the cell growth phase. The glycerol production phase was extended several-fold by periodic glucose addition. The yeast cell count remained constant during this time as limited by phosphate, a deficiency required for an efficient glycerol fermentation. A small amount of phosphate was supplied during the extended fermentation, maintaining an active culture, by the normal autolysis of spent cells. Interfering or inhibitory by-products did not accumulate, and the osmophilic yeasts are tolerant of high glycerol concentrations. These factors combined to allow a particularly efficient fermentation well suited to product enrichment by supplying large quantities of substrate over an extended period.