The relationship between erythritol production and osmotic pressure of the medium was investigated with Trigonopsis variabilis. The concentration of intracellular erythritol reached the maximum at 5th day of culture and then decreased gradually. To investigate the effect of osmotic pressure, cells were grown on media containing various concentrations of solutes. Solutes added to adjust the osmolality of media were glucose, KCl, and NaCl. As osmolality of the medium increased, the yield of erythritol also increased, but the cell growth rate was adversely affected. Among three solutes, NaCl showed the highest enhancing effect on the yield of erythritol, but the concentration of erythritol was very low due to severe inhibitory effect of NaCl on cell growth. Trigonopsis variabilis was more tolerant to glucose than to NaCl or KCl at equivalent osmolality. NaCl was found to be the most inhibitory to the cell growth of Trigonopsis variabilis. It revealled that the cell growth was also affected by properties of added solutes. Higher amounts of erythritol were produced at equivalent osmolality when adjusted with glucose than with KCl or NaCl, and thus glucose was considered to be the most suitable solute for the adjustment of osmolality. Batch fermentations were carried out in a 5L jar fermentor with glucose concentration of 10% and 30%. At 10% glucose, erythritol concentration and erythritol yield were 8.7g/l and 0.08g/g-glucose utilized, respectively. In case of 30% glucose, erythritol concentration and yield were 24.3g/l and 0.19g/g-glucose utilized, respectively. In two-step fermentation differing the osmolality, erythritol concentration reached 41.3g/l, with a yield of 0.24 g erythritol/g-glucose utilized, which showed the increase by 1.7 times in erythritol concentration and 1.3 times in yield compared with those obtained in batch culture.
