Comparative studies on pullulan synthesis, melanin synthesis and morphology of white mutant Aureobasidium pullulans B-1 and parent strain A.p.-3

A mutant with reduced pigmentation was isolated from Aureobasidium pullulans A.p.-3 by physical mutagenesis. The ability to synthesize pullulan and melanin was compared between the mutant and the parent strain. Morphological differences between the strains were observed under scanning and transmission microscope (SEM and TEM). The chemical structure of the pullulan synthesized by the strains evaluated was compared using FT-IR spectroscopy with that of pullulan available commercially.The amount of pullulan synthesized by the mutant and parent strains was similar whereas the melanin content was significantly reduced. The chemical structure of the pullulan was the same as that of the pullulan from commercial sources. The changes in the appearance of mutant capsules were observed under SEM. Smaller amount, lower size of the melanin molecules and their dislocation influenced the brightness of mutant chlamydospores.