Abstract: The effect of different substrates such as glucose, sucrose and xylose on the production of pullulan by Aureobasidium pullulans CCTCC M 2012259 in batch fermentation was investigated. It was shown that sucrose was favorable to improve pullulan production to a maximum titer of 72.33 g/L, while glucose was propitious to achieve pullulan with a maximum final molecular mass of 5.9 × 105 Da. The fermentation kinetic parameters with different substrates were calculated and physiological and biochemical indexes were determined. Sucrose was indicated to increase the activities of key enzymes involved in the metabolic pathway for pullulan biosynthesis, improve the levels of intracellular uridine diphosphate glucose (UDPG), and increased the energy supply from ATP, ultimately resulting in an improvement of pullulan production. In addition, glucose decreased the activity of pullulan-degrading enzyme during batch fermentation, helping to maintain the molecular mass of pullulan at a higher level. The results presented in this study partially revealed the physiological mechanism underlying the effect of substrates on pullulan biosynthesis, which will provide a feasible approach for efficient production of pullulan with different molecular masses.

Key words: Aureobasidium pullulans, pullulan, glucose, sucrose, xylose, batch fermentation