Production of D-arabitol from raw glycerol by Candida quercitrusa.

To promote the effective use of raw glycerol (a by-product of biodiesel production), 110 yeast strains that produce D-arabitol from glycerol were isolated from environmental samples. Among them, strain 17-2A was an effective D-arabitol producer in the presence of 250 g/l glycerol and was identified as Candida quercitrusa based on morphological, physicochemical, and phylogenetic analyses. C. quercitrusa type strain NBRC1022 produced the greatest quantity of D-arabitol (41.7 g/l) when the ability to produce D-arabitol from raw glycerol was compared among C. quercitrusa 17-2A and its phylogenetically related strains in flask culture. Under optimized culture conditions, strain NBRC1022 produced D-arabitol at a concentration of 58.2 g/l after a 7-day cultivation in 250 g/l glycerol, 6 g/l yeast extract, and 2 g/l CaCl2. The culture conditions were further investigated with raw glycerol using a jar fermenter; the concentration of D-arabitol reached 67.1 g/l after 7 days and 85.1 g/l after 10 days, respectively, which corresponded to 0.40 g/g of glycerol. To our knowledge, the present D-arabitol yield from glycerol is higher than reported previously using microbial production.