No abstract

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

The action of purified α‐amylase of Streptomyces precox NA‐273 on starch granules of normal maize and potato was studied. The hydrolysis was followed by measuring total soluble carbohydrates and glucose released. Patterns of degradation were observed by scanning electron microscopy (SEM). The main soluble product was maltose, small amounts of glucose and higher oligosaccharides were always observed. By SEM, attack started small pits on the surfaces of maize starch granules, pits increased in number and in size, and pores penetrated into the inner portions of the granules toward the center. The enzyme seemed to degrade the inner portion of starch granules better than the well‐known general α‐amylases.

No abstract

No abstract