Production of exopolysaccharides and morphological changes in shake-flask culture of Aureobasidium pullulans grown on three different nitrogen sources
出芽短梗霉在三种不同氮源的培养基中多糖积累以及形态变化

In this study, morphological changes and the production of exopolysaccharides (EPS) by Aureobasidium pullulans were determined by growing the fungus in different nitrogen (N) sources media, which included NaNO3 (medium 1, M1), yeast extract and (NH4)2SO4 (medium 2, M2) and yeast extract, peptone and (NH4)2SO4 (medium 3, M3). Less biomass of mycelia and unicells occurred in M1, but EPS production was comparatively similar to those determined in M2 and M3. At early exponential stage, the population of A. pullulans was characterized by the presence of predominant yeast-like cells and unmelaninized mycelia. At late exponential stage, these were substituted by chlamydospores, swollen cells and melaninized mycelia. EPS produced by the fungus in the three N sources were all able to be hydrolysed by pullulanase. The hydrolytic products were maltose and maltotriose from EPS produced in M1 with almost equal molar ratio, but the ratio of maltose was remarkably decreased in M2 and disappeared from M3 after incubation for 144h. These results suggest that the oxidant N source and low dissolved oxygen might be responsible for the co-presence of maltose and maltotriose as structural units of EPS produced by the fungus.