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Two forms of erythrose reductave (ER-1 and ER-2) were purified from an Aureobasidium sp. mutant having high erythritol-producing activity besides the one (ER-3) reported previously. They were purified by chromatofocusing or hydrophobic chromatography after being separated from ER-3 on affinity chromatography. Physicochemical and enzymatic properties of the three forms were compared.Molecular weights were estimated to be 38,000 for ER-1 and 37,000 for ER-2 and ER-3 by SDS-PAGE. Isoelectric points of ER-1, ER-2, and ER-3 were 5.2, 5.0, and 4.8, respectively. All three forms behaved similarly toward pH and temperature, and showed maximum activity at pH 6.5 and 45°C. They showed essentially the same pH-and temperature-stability. D-Erythrose was the best substrate and D-glyceraldehyde, L-erythrulose, and dihydroxyacetone followed. No other aldose and ketose were reduced. There was no significant difference in the substrate specificity of the three forms. Their Km and Vmax for D-erythrose were found to be around 8 mM and 0.38-0.63 ,umol/min/mg, respectively. Significant differences were observed in the behavior of the three forms toward metal ions such as Ag+, Fe3+, and A13+. They showed no oxidative activity at neutral pH but showed some activity at alkaline conditions. Although the activity toward erythritol was much lower (less than 0.1%) compared with the reductive activity, the three forms showed remarkable diversity in pH-activity profile and substrate specificity.Aureobasidium sp. SN-G42 (6), a mutant isolated from Aureobasidium sp. SN-124A, is one of the strains used for commercial production of erythritol. This strain

Erythritol in various natural cheeses was quantitatively determined using high-performance liquid chromatography (HPLC). The peak detected at the position of erythritol by HPLC was identified by gas chromatographymass spectrometry (GC-MS). Erythritol was detected in cheese samples ripened with fungi and contents ranged from 0.01-2.96 mg/g, and surface-ripened cheeses with white fungi especially contained more erythritol compared to blue-vein cheeses with blue fungi inside. No erythritol was found in cheese samples ripened with bacteria and without ripeness. In the case of surface-ripened cheeses, much more amounts (1.99-6.86 mg/g) of erythritol was found in their surface part compared to the inner part (0-0.33 mglg). These results seem to suggest that erythritol is being produced by conventional microorganisms, Penicillium sp., used in ripeness.