Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 72 Wenhua Road, 110016, China.
Jiangsu Collaborative Innovation Center of Regional Modern Agricultural & Environmental Protection/Jiangsu Key Laboratory for Eco-Agricultural Biotechnology around Hongze Lake, Huaiyin Normal University, Huaian, 223300, China.
Braz J Microbiol. 2021 Mar;52(1):257-265. doi: 10.1007/s42770-020-00396-w. Epub 2020 Nov 4.
As a key precursor of vitamin C, 2-keto-L-gulonic acid (2-KLG) was mainly produced from L-sorbose by mixed fermentation of Ketogulonicigenium vulgare and a helper strain (Bacillus spp.) with a low conversion rate for decades. The aim of this study was to enhance the 2-KLG production by co-culturing K. vulgare and Bacillus megaterium using three-stage temperature control (TSTC) strategy. By investigating the temperature effect on the 2-KLG fermentation, the optimum temperatures for the growths of K. vulgare and B. megaterium were 32 °C and 29 °C, respectively, while the optimum temperature for 2-KLG production was 35 °C. We developed a TSTC process: the temperature was kept at 32 °C during the first 16 h of fermentation, then decreased to 29 °C for the following 14 h, and maintained at 35 °C to the end of fermentation. By using this new process, the productivity and yield of 2-KLG from L-sorbose were obtained at 2.19 ± 0.19 g/L/h and 92.91 ± 1.02 g/L in 20-L fermentors for 5 batches, respectively, which were 22.35% and 6.02% higher than that of the control treatment (the single temperature of 29 °C). The increased cell density of K. vulgare during the exponential phase and the enhanced SDH activity (increased by 25.18% at 36 h, 17.14% at 44 h) in the production stage might be the reasons for enhanced 2-KLG conversion rate and yield. Our results demonstrated the feasibility of the TSTC strategy for 2-KLG production.
作为维生素 C 的关键前体，2-酮-L-古洛糖酸（2-KLG）主要由 L-山梨糖经酮古龙酸发酵和辅助菌株（芽孢杆菌属）混合发酵生产，但几十年来转化率一直较低。本研究旨在通过采用三阶段温度控制（TSTC）策略，利用酮古龙酸发酵和巨大芽孢杆菌共培养来提高 2-KLG 的产量。通过研究温度对 2-KLG 发酵的影响，确定了酮古龙酸和巨大芽孢杆菌的最佳生长温度分别为 32°C 和 29°C，而 2-KLG 生产的最佳温度为 35°C。我们开发了一种 TSTC 工艺：发酵前 16 小时保持温度为 32°C，然后降至 29°C 持续 14 小时，最后保持 35°C 直至发酵结束。使用这种新工艺，在 20-L 发酵罐中进行了 5 批实验，从 L-山梨糖获得的 2-KLG 的生产率和产率分别达到 2.19±0.19 g/L/h 和 92.91±1.02 g/L，比对照处理（单一温度 29°C）分别提高了 22.35%和 6.02%。在指数生长期增加了酮古龙酸的细胞密度，在生产阶段增强了 SDH 活性（36 小时时提高了 25.18%，44 小时时提高了 17.14%），这可能是提高 2-KLG 转化率和产率的原因。我们的结果证明了 TSTC 策略在 2-KLG 生产中的可行性。
