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Aureobasidium pullulans produced high concentration of polyols extracellularly in the media of sucrose, glucose and mannose as sole carbon source. Mannitol was the main polyol produced during the late exponential and stationary phases of growth together with small quantities of glycerol. Sucrose and glucose were rather rapidly metabolized to mannitol among carbon sources examined where the initial glucose concentration showed no difference in the amount of mannitol. In contrast, 20%(w/v) of sucrose was the most appropriate concentration tested. However, the yield of mannitol based on substrate used(Yp/s) was independent on the initial concentration, and the mean value of mannitol yield in 10% glucose and sucrose media was 0.144 and 0.188, respectively. Mannitol production was reduced in response to an elevated water stress imposed by salts within the range from 0.25 to 1M of NaCl or KCI as stress solutes. However, glycerol contents and its ratio to mannitol were increased at the conditiu,ls of high salinity. Based on the results, extracellular mannitol produced by A. pullulans probably resulted partly from osmoregulation(in case of glycerol) and mainly from, as known to occur in most of fungi, enzymatic reduction of the corresponding hexoses through phosphate pathway.
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