Abstract: The effects of surfactants, Span and Tween, on pullulan production by bioconversion using whole cells of Aureobasidium pullulans were investigated. The pullulan biosynthesis capability of these cells was increased by 46.5% and 32.9%, respectively, when Span 80 (20 g/L) and Tween 80 (5 g/L) were added individually into the bioconversion broth. The combination of the two surfactants further improved the yield and efficiency of pullulan production. Based on the determined physiological and biochemical parameters, Span 80 and Tween 80 were found to improve the permeability of the cell membrane, increase the activities of the key enzymes involved in pullulan biosynthesis, elevate the levels of intracellular uridine diphosphate glucose and energy substance ATP, and accelerate the rate of ATP regeneration, promoting the metabolism of substance and energy and ultimately resulting in improvement in the yield and efficiency of pullulan production. The results presented in this study partly elucidate the physiological mechanism underlying the increase in efficiency of pullulan production by surfactants and also provide a technical basis for efficient production of other analogous microbial polysaccharides.

Key words: Aureobasidium pullulans, pullulan, bioconversion, biosynthesis efficiency, Span 80, Tween 80