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