底物的分散和溶解对甾体微生物酶反应的影响

甾体的溶解是微生物转化反应的控制步骤。表面活性剂对憎水性物质的增溶作用是具有憎水内核胶团形成的直接结果。随表面活性剂溶液浓度的增加，胶团数目增加，甾体水溶性增强。复配型分散剂PSE－MGE应用于甾体转化体系，相对于单组分分散剂PSE而言，实现同一程度甾体水溶性增强所需的表面活性剂用量减少，对菌体生长的负面影响较小，有利于转化。超声与分散剂配合使用的效果优于分解剂单独使用的效果，且使用较强的超声声强（12.4W/cm^2）和较短的超声时间（5min）时效果最佳。

EFFECTS OF SUBSTRATE DISPERSION AND DISSOLUTION ON MICROBIAL ENZYMATIC CONVERSION OF STEROID

The dissolution of substrate is the key step in steroid microbial conversion.The formation of surfactant micelle with a hydrophobic center directly results in increased pseudo-water-solubilities of hydrophobic compounds such as steroids.Results showed increased water solubility of steroid with the increased surfactant concentrations.Compared to mono-surfactant PSE,less quantity of multiple surfactants PSE-MGE was required to achieve the enhancement of steroid solubility at the same level,thus the negative effects of surfactants on mycelial growth were reduced and steroid conversion was therefore improved more.It was also shown that the surfactants and ultrasonic irradiation used jointly could result in better substrate dispersion and dissolution than surfactants used alone,and the best result was obtained when the comparatively high intensity (12.4 W/cm 2) and short time (5min) of ultrasonic irradiation were performed.