摘要
Rhizopus oryzae, associated with the post-harvest spoilage of cassava, produced high levels of extracellular rhodanese during exponential phase of growth. The fungus could grow and yield more rhodanese at pH 4.6–5.4 and temperature 30–35°C; however, the optimum assay condition of the enzyme was found to be at a temperature of 40°C and pH 6.0. Glucose or other low molecular weight metabolizable sugars did not repress the synthesis of rhodanese, indicating the lack of catabolite repression in this organism. Of the nitrogen sources examined, peptone, yeast extract and nitrate salts enhanced the yield of rhodanese. The addition of surfactants, such as Tween 80 at 0.1 % level to fungal culture media markedly increased rhodanese production. Potassium cyanide (KCN) at 0.25 and 0.5 mM levels was found to induce rhodanese synthesis; beyond these levels, it completely suppressed the cell growth. However, spores adapted to 0.5 mM KCN level could grow in media containing 4mM KCN but exhibited less rhodanese activity compared with the non-adapted culture. Rhodanese activity was also related to the oxidation of thiosulphate and elemental sulphur to sulphate by the fungus.
摘要译文
与木薯收获后腐败有关的米根霉（Rhizopus oryzae）在指数生长期间产生高水平的细胞外硫氰酸酶。真菌可在pH4.6-5.4和温度30-35℃下生长并产生更多的硫氰酸酶;然而，发现酶的最佳测定条件是在40℃和pH6.0的温度下。葡萄糖或其他低分子量可代谢糖不抑制硫氰酸酶的合成，表明该生物体中缺乏分解代谢物抑制。在所检查的氮源中，蛋白胨，酵母提取物和硝酸盐增强了硫氰酸酶的产量。向真菌培养基中添加0.1％Tween 80的表面活性剂显着增加了硫氰酸盐的产量。发现0.25和0.5mM水平的氰化钾（KCN）诱导硫氰酸合成;超过这些水平，它完全抑制细胞生长。然而，适应0.5mM KCN水平的孢子可以在含有4mM KCN的培养基中生长，但与未适应的培养物相比表现出较少的硫氰酸酶活性。 Rhodanese活性也与真菌对硫代硫酸盐和元素硫氧化成硫酸盐有关。
Ramesh C.Ray[*];G.Padmaja[*];C.Balagopalan[*];. Extracellular rhodanese production by Rhizopus oryzae[J]. Zentralblatt für Mikrobiologie, 1990,145(4): 259-268