Isolation and identification of a strain of Aureobasidium pullulans and its production of polysaccharide

【Objective】An Aureobacidium pullulans strain able to produce pullulans was screened to provide strains for pullulans fermentation industry. 【Method】Nine soil samples were taken from the grassland of Poyang lake national wetland park. Plate dilution method was used to separate fungus. The colony morphology and cell morphology of fungus were observed, and the sequence of 18 s rDNA of fungus was analyzed. Then, a new strain of Aureobasidium pullulans was isolated. Fermental cultivation was also conducted for measuring colour and yield of pulluans, and the structure of polysaccharide was determined by infrared spectroscopy(FT-IR). 【Result】Five candidate fungus were isolated from the nine soil samples. After purified and cultured, it was found that only Strain AP23 had morphological diversity, such as yeast and mycelium. It was considered that strain AP23 was Aureobasidium pullulans. The yield of pullulans was 6.72 g/L and sugar conversion rate was 22.4%. Infrared spectrum(FT-IR) verified that pullulans were consisted of Alpha glycosidic bond connection of D- pyran glucose residues. 【 Conclusion 】 Aureobasidium pullulans AP23 has good growth characteristics, hence it can be utilized for pullulan fermentation industry.