[Optimization of biotransformation of ursolic acid by alternaria longipes].

To conduct the biotransformation of ursolic acid by alternaria longipes AS3. 2875, and optimize the culture medium and biotransformation conditions. With the consumption rate of ursolic acid and the generation rate of 28-O-beta-D-glucopyranose ursolic acid as indicators, the impact of different biotransformation conditions such as pH, phosphate, different kinds of metal ions, spore concentration, substrate quantity, temperature, shaking speed and cultivation time on the transformation of ursolic acid in alternaria longipes culture solution were detected to obtain the optimal biotransformation conditions of ursolic acid by alternaria longipes. The optimized biotransformation conditions were as follows: initial pH value was 5.0, MgSO4 was 0.25 g x L(-1) K2HPO4 was 1.0 g x L(-1), FeSO4 was 0.083 g x L(-1), spore concentration was 4%, substrate quantity was 0.3 g x L(-1), shaking speed was 140 r x min(-1), cultivation temperature was at 28 degrees C and cultivating time was 3 days. The generation rate of 28-O-beta-D-glucopyranose ursolic acid by alternaria longipes stabilizes at around 5%.