Optimization of conditions for the production of pullulan and high molecular weight pullulan by Aureobasidium pullulans

Aureobasidium pullulans had a maximum yield coefficient of pullulan (Y_p/s=0.24) with an initial pH of the culture broth of 6.5 in a shake-flask culture. In a batch culture, the maximum pullulan yield coefficient of 0.30 was obtained at the aeration rate of 0.5 vvm. A yeast-like form and mycelial form of cells were found at the culture broth with pH controlled at 4.5 with a maximum yield coefficient of pullulan of 0.27. However, a high portion (35%) of high molecular weight pullulan (M_w>2 000 000) was produced at pH 6.5 with a yeast-like morphology of the cells.