Enhancement of 2-keto-L-gulonic acid production using three-stage pH control strategy / 生物工程学报

The aim of this study was to improve the 2-keto-L-gulonic acid (2-KLG) production efficiency by Ketogulonicigenium vulgare and Bacillus megaterium by using multi-stage pH control strategy. The effect of pH on the cell growths and 2-KLG production showed that the optimum pH for K. vulgare and B. megaterium cell growth were 6.0 and 8.0, respectively, while the optimum pH for 2-KLG production was 7.0. Based on the above results, we developed a three-stage pH control strategy: the pH was kept at 8.0 during the first 8 h, then decreased to 6.0 for the following 12 h, and maintained at 7.0 to the end of fermentation. With this strategy, the titer, productivity of 2-KLG and L-sorbose consumption rate were achieved at 77.3 g/L, 1.38 g/(L x h) and 1.42 g/(L x h), respectively, which were 9.7%, 33.2% and 25.7% higher than the corresponding values of the single pH (pH 7.0) control model.

Enhancing 2-keto-L-gulonic acid production under hyperosmotic stress by adding sucrose / 生物工程学报

This study aimed to further enhance 2-keto-L-gulonic acid (2-KLG) production efficiency. A strategy for enhancing Ketogulonigenium vulgare growth and 2-KLG production by improving B. megaterium growth with sucrose was developed based on the time course of osmolality during 2-KLG industrial scale fermentation and effects of osmolality on cells growth and 2-KLG production. Results showed that the accumulation of 2-KLG and the feeding of alkaline matter led to an osmolality rise of 832 mOsmol/kg in the culture broth. High osmotic stress (1 250 mOsmol/kg) made the growth ofB. megaterium and K. vulgare decreased 15.4% and 31.7%, respectively, and consequently the titer and productivity of 2-KLG reduced 67.5% and 69.3%, respectively. When supplement sucrose under high osmotic condition (1 250 mOsmol/kg), B. megaterium growth was significantly improved, with the result that 2-KLG production was increased 87%. Furthermore, by applying this sucrose addition strategy further to batch fermentation in 3 L fermentor, the productivity of 2-KLG increased 10.4%, and the duration of fermentation declined 10.8%. The results presented here provide a potential strategy for enhancing the target metabolites produced by mixed strains at environmental stress.