高渗条件下利用蔗糖提升2-酮基-L-古龙酸生产效率

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

摘要:

旨在进一步提升维生素C前体2-酮基-L-古龙酸 (2-KLG) 的生产效率。在详细考察了2-KLG工业化生产过程中渗透压变化规律的基础上，研究了高渗对混合菌系细胞生长和2-KLG合成的影响，提出蔗糖促进伴生菌巨大芽胞杆菌Bacillus megaterium生长，进而促进普通生酮古龙酸菌Ketogulonigenium vulgare生长和产酸的策略。结果表明，2-KLG的积累和碱性物质的流加使渗透压上升了832 mOsmol/kg；高渗抑制了巨大芽胞杆菌的生长 (15.4％)，从而抑制普通生酮古龙酸菌 (31.7％) 的生长，导致2-KLG产量和生产强度分别下降67.5％和69.3％ (以1 250 mOsmol/kg为例)；蔗糖的添加则显著促进巨大芽胞杆菌的生长，使高渗条件下 (摇瓶，1 250 mOsmol/kg) 2-KLG产量 (40.6 g/L) 提高87％；在3 L发酵罐中，补加10 mmol/L蔗糖使2-KLG发酵周期缩短10.8％，2-KLG生产强度提高10.4％。研究成果为在环境胁迫下提高混菌生产目标代谢产物的产量提供了潜在的策略。

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.