Study on the control technology of pullulan fermentation

Abstract

Pullulan, as an important linear extracellular polysaccharide, is mainly produced by Aureobasidium pullulans through a specific biosynthetic pathway. Its structure is based on the tight connection of the repeat unit of maltotriose through α-(1-6) glycosidic bonds this unique chemical structure gives pullulan a series of remarkable physical and chemical properties, such as high-water solubility, excellent film-forming ability, excellent oxygen resistance, good plasticity, low viscosity and easy biodegradation. In this paper, the carbon source of pullulan produced by Aureobasidium pullulans was studied, and the effects of various metal ions on pullulan biosynthesis were compared through a large number of experiments in order to obtain a better medium formula. finally, the effects of continuous fermentation and fermenter fermentation on pullulan production by Aureobasidium pullulans were studied. In the experiment of studying the effects of continuous fermentation and fermenter fermentation on the production of pullulan by Aureobasidium pullulans, the changes of sugar production by Aureobasidium pullulans under different conditions were systematically explored through shaking table and fermenter experiments. The results showed that 30 ℃ was favorable for the growth of Aureobasidium pullulans, while 28 ℃ was more suitable for pullulan synthesis. In batch culture, pullulan production and cell growth rate reached the peak at 400 rpm speed, while 220 rpm speed was the best for shake flask culture. In the experiment of the effect of different carbon source combinations on pullulan production by Aureobasidium pullulans, the effects of sucrose, glucose and fructose as carbon sources on pullulan production by Aureobasidium pullulans were deeply compared. combined with the combination of the three carbon sources, the corresponding fermentation parameters were obtained. The experimental data showed that although sucrose as a carbon source achieved the highest yield in the process of pullulan biosynthesis, the carbon source combination of fructose and glucose at 1:1 showed significant economic advantages and potential for development. In the experiment of studying the effect of different metal ions on pullulan production by Aureobasidium pullulans, the optimal concentration of each metal ion was obtained by adding magnesium, iron, copper, zinc, calcium, manganese and other metal ions to the culture medium. The results showed that the types and concentrations of trace elements had significant effects on the polysaccharide yield of Aureobasidium pullulans, and the yield was significantly different under different combinations and concentrations, and the best concentrations were 0.05 g/L MnCl2, 0.05 g/L ZnSO4, 0.15 g/L CaCl2, 0.1 g/L CuSO4, 0.06 g/L FeSO4 and 0.2 g/L MgSO4.