Enhancing 2-keto-L-gulonic acid production under hyperosmotic stress by adding sucrose

Abstract:

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 of B. 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.

Key words:mixed culture, 2-keto-L-gulonic acid, carbon source regulation, Vitamin C, hyperosmotic stress