RESUMO
The effects of several surfactants on the biosynthesis of ß-1,3-D-glucan (ß-glucan) and pullulan by Aureobasidium pullulans CCTCC M 2012259 were investigated, and Triton X-100 was found to decrease biomass formation but increase ß-glucan and pullulan production. The addition of 5 g/L Triton X-100 to the fermentation medium and bioconversion broth significantly increased ß-glucan production by 76.6% and 69.9%, respectively, when compared to the control without surfactant addition. To reveal the physiological mechanism underlying the effect of Triton X-100 on polysaccharides production, the cell morphology and viability, membrane permeability, key enzyme activities, and intracellular levels of UDPG, NADH, and ATP were determined. The results indicated that Triton X-100 increased the activities of key enzymes involved in ß-glucan and pullulan biosynthesis, improved intracellular UDPG and energy supply, and accelerated the transportation rate of precursors across the cell membrane, all of which contributed to the enhanced production of ß-glucan and pullulan. Moreover, a two-stage culture strategy with combined processes of batch fermentation and bioconversion was applied, and co-production of ß-glucan and pullulan in the presence of 5 g/L Triton X-100 additions was further improved. The present study not only provides insights into the effect of surfactant on ß-glucan and pullulan production but also presents a feasible approach for efficient production of analogue exopolysaccharides. KEY POINTS: ⢠Triton X-100 increased ß-glucan and pullulan production under either batch fermentation or bioconversion. ⢠Triton X-100 increased the permeability of cell membrane and accelerated the transportation rate of precursors across cell membrane. ⢠Activities of key enzymes involved in ß-glucan and pullulan biosynthesis were increased in the presence of Triton X-100. ⢠Intracellular UDPG levels and energy supply were improved by Triton X-100 addition.
