Efficient Production of Gellan Gum in Sphingomonas Paucimobilis ZJU 311 with Fermentation Condition Optimization and Kinetic Analyses
|Keywords||gellan gum Sphingomonas paucimobilis fermentation conditions kinetic model|
Gellan gum is one of the industrially useful exopolysaccharides produced by Sphingomonas paucimobilis. Compared with other polysaccharides, It has many advantages such as excellent thermal and acid stability, adjustable gel elasticity and rigidity, high transparency and good flavor releasing, and can be widely used in food, pharmaceutical and other industries. The objective of this paper is to develop an efficient fermentation bioprocess in Sphingomonas paucimobilis ZJU 311 with fermentation condition optimization and kinetic modeling.The culture conditions of Sphingomonas paucimobilis ZJU 311was studied firstly. Then the culture medium compositions for gellan gum production were investigated by using single-factor experiments. Then Plackett-Burman design was subsequently applied to screen the most important factors of all related medium components. The results showed that soybean meal, MnCl2.4H2O, L-Proline were the main affecting factors on gellan gum fermentation. Then the optimum fermentation medium was determined according to CCD (Central composite Design) and response surface analysis with SAS software. The optimal fermentation medium for gellan gum production was obtained which could support the high yield of gellan gum (18.7g/L) with about 72% improvement over the original medium.Finally, the batch fermentation process of gellan gum was scaled up in the 10L bench-top bioreactor. The effects of temperature and stirring rate on gellan gum fermentation were studied thoroughly. One two-step temperature strategy was adopted to improve the productivity. And one stirring rate control method was also developed which consisted of:400rpm till 24h,850rpm till the end of fermentation. With the above strategies, high yield and productivity of gellan gum were achieved in this bench-top fermentor.Kinetic analyses for the gum biosynthesis were further studied in this 10L bioreactor. Mathematic models of cell growth, product generation and substrate consumption in batch fermentation were proposed according to the Logistic equation and the Luedeking-Piret equation. By the comparison with the experimental data, our proposed models can be used to simulate the fermentation process for enhanced production of gellan gum production with Sphingomonas paucimobilis ZJU 311.