复合诱变选育短梗霉多糖高产菌株

以本实验室保存的出芽短梗霉AP8为出发菌株，采用甲基磺酸乙酯(EMS)和紫外线(UV)复合诱变，在EMS终浓度0.4mol/L、作用时间40～60min和30W的紫外灯照射距离30cm、照射时间1.5～2.5min条件下诱变效果好，获得一株稳定遗传的多糖产量高、色素含量低的出芽短梗霉突变株UV60，产量为22.1g/L，对菌落特征和发酵特征的比较发现，突变株UV60在菌落颜色、大小、质地和发酵特性上均明显优于出发菌株AP8。通过对变异株培养基碳氮比和培养基的组成进行单因素和正交试验，其最佳摇瓶发酵培养基组成为：蔗糖50.0g/L、酵母膏1.5g/L、NaCl 1.5g/L、MgSO4 0.3g/L、K2HPO4 2.0g/L、(NH4)2SO4 0.7g/L。采用上述优化的发酵培养基，突变株UV60获得的短梗霉多糖产量为27.24g/L，多糖转化率达54.48%。

Combined Mutation Screening of High Yield Strain for Pullulan Production

Aureobasidium pullulans AP8, an original strain conserved in our laboratory, was treated with both EMS (ethyl methyl sulfonate) and UV (ultraviolet) to screen a high yield strain for pullulan production. The best mutation results were obtained through EMS treatment for 40-60 min at a final concentration of 0.4 mol/L followed by UV irradiation for 1.5-2.5 min at a distance of 30 cm. A genetically stable mutant named as UV60 was obtained which is high in pullulan production (22.1 g/L) and low in pigment content. The mutant strain was markedly superior to the starting strain AP8 in terms of colony color, size and texture as well as fermentation performance. Using one-factor-at-a-time and orthogonal array design methods, the optimal shake fermentation medium for this mutant to produce pullulan was composed of 50.0 g/L sugar, 1.5 g/L yeast extract, 1.5 g/L NaCl, 0.3 g/L MgSO4, 2.0 g/L K2HPO4 and 0.7 g/L (NH4)2SO4, resulting in a pullulan yield of 27.24 g/L and a conversion rate of 54.48% for polysaccharides.