生物转化提高黄芪多糖含量的发酵条件优化

以黑曲霉（Aspergillus niger）为出发菌株，黄芪提取液为唯一碳源进行生物转化。在单因素试验的基础上采用正交试验设计，以黄芪多糖含量为指标对发酵条件中的发酵时间、发酵温度、起始pH及摇床转速进行优化。结果表明，在起始pH 5.0、发酵温度30 ℃、摇床转速180 r/min的条件下发酵6 d，黄芪多糖含量最高，为（2.473±0.062）g/L。利用红外光谱分析发酵前后黄芪多糖的结构变化，结果表明发酵前后黄芪多糖的结构没有发生较大变化。

Optimization of fermentation conditions for increasing Astragalus polysaccharide contents by biotransformation

The biotransformation was carried out with Aspergillus niger as the starting strain and Astragalus extraction as the only carbon source. The orthogonal experiments were designed on the basis of single factor experiments. The optimized fermentation conditions were investigated by orthogonal experiments with the content of Astragalus polysaccharide as the index which was determined by fermentation time, temperature, initial pH and shaker speed. The results showed that the content of Astragalus polysaccharide was the highest of (2.473±0.062) g/L and the concentration of polysaccharide was increased by 76% under the conditions of initial pH 5.0, fermentation temperature 30 ℃, shaker speed 180 r/min and fermentation time 6 d. The structural changes of Astragalus polysaccharides before and after fermentation were analyzed by infrared spectroscopy, and the results showed that there was little change in structurae of Astragalus polysaccharides before and after fermentation.