高产无色素普鲁兰糖突变菌株P1012的选育及发酵性能研究

本研究旨在选育出高产普鲁兰多糖且黑色素分泌缺失的菌株,为普鲁兰的发酵生产提供宝贵的菌种资源。研究采用三种诱变剂(紫外线(UV)、亚硝基胍(NTG)、硫酸二乙酯(DES))对出发菌株茁芽短梗霉P23进行多轮诱变处理。通过从PDA平板上挑选出色素低且黏度大的菌落作为候选菌株,并经红外光谱(FT-IR)分析其胞外多糖的构型。结果筛选出13株候选菌株,其中菌株P1012于PDA平板上培养7 d形成的菌落为白色,96 h发酵液呈乳白色,且吸光值(OD654 nm表示色素的相对含量)达到0.048,其胞外多糖经红外光谱检测可初步分析为普鲁兰多糖,与出发菌株P23相比,菌株P1012主要表现在细胞合成色素上的缺失。发酵培养后,测得普鲁兰产量为28.01 g/L,糖转化率达到56.02%,糖转化率比出发菌株高出28.8%。表明菌株P1012可以作为生产普鲁兰多糖的候选菌株。

Screening of Non-pigmented Aureobasidium pullulans Strain P1012 for High-yield Pullulan Production

The purpose of this study was to screen for a strain with a high pullulan yield without production of the black cell pigment, which would be a valuable strain for pullulan production. Aureobasidium pullulans strain P23 was mutated several times using three mutagens: ultraviolet (UV) light, 1-methyl-3-nitro-1-nitroso-guanidine (NTG), and diethyl sulfate (DES). Strains with high viscosity and low pigmentation were selected on potato dextrose agar (PDA) plates. The structure of exopolysaccharides produced by the selected strains was analyzed by Fourier transform infrared (FT-IR) spectroscopy. Based on the results, 13 candidate strains were selected and one mutant strain, P1012, formed white colonies on PDA plates incubated for seven days; in broth, the growth appeared ivory-white after 96 h with light absorbance (OD654nm, to demonstrate relative pigment content) at 0.048. The exopolysaccharide produced by strain P1012 was identified as pullulan by FT-IR. Compared with P23, P1012 showed a lack of cellular pigmentation. The pullulan yield via fermentation by strain P1012 was 28.01 g/L and the sugar conversion rate was 56.02%, 28.8% higher than that of the original strain P23. This study showed that strain P1012 could be a candidate strain for industrial production of pullulan.