Wang Jinduo, Wang Shuo, Zhao Siyu, Sun Pengjie, Zhang Zhen, Xu Qingyang
National and Local United Engineering Lab of Metabolic Control Fermentation Technology, Tianjin University of Science and Technology, Tianjin, China.
College of Biotechnology, Tianjin University of Science and Technology, Tianjin, China.
Front Bioeng Biotechnol. 2023 May 3;11:1181963. doi: 10.3389/fbioe.2023.1181963. eCollection 2023.
L-lysine is a bulk product. In industrial production using high-biomass fermentation, the high density of bacteria and the intensity of production require sufficient cellular respiratory metabolism for support. Conventional bioreactors often have difficulty meeting the oxygen supply conditions for this fermentation process, which is not conducive to improving the sugar-amino acid conversion rate. In this study, we designed and developed an oxygen-enhanced bioreactor to address this problem. This bioreactor optimizes the aeration mix using an internal liquid flow guide and multiple propellers. Compared with a conventional bioreactor, it improved the ka from 367.57 to 875.64 h, an increase of 238.22%. The results show that the oxygen supply capacity of the oxygen-enhanced bioreactor is better than that of the conventional bioreactor. Its oxygenating effect increased the dissolved oxygen in the middle and late stages of fermentation by an average of 20%. The increased viability of LS260 in the mid to late stages of growth resulted in a yield of 185.3 g/L of L-lysine, 74.57% conversion of lysine from glucose, and productivity of 2.57 g/L/h, an increase of 11.0%, 6.01%, and 8.2%, respectively, over a conventional bioreactor. Oxygen vectors can further improve the production performance of lysine strains by increasing the oxygen uptake capacity of microorganisms. We compared the effects of different oxygen vectors on the production of L-lysine from LS260 fermentation and concluded that n-dodecane was the most suitable. Bacterial growth was smoother under these conditions, with a 2.78% increase in bacterial volume, a 6.53% increase in lysine production, and a 5.83% increase in conversion. The different addition times of the oxygen vectors also affected the final yield and conversion, with the addition of oxygen vectors at 0 h, 8 h, 16 h, and 24 h of fermentation increasing the yield by 6.31%, 12.44%, 9.93%, and 7.39%, respectively, compared to fermentation without the addition of oxygen vectors. The conversion rates increased by 5.83%, 8.73%, 7.13%, and 6.13%, respectively. The best results were achieved by adding oxygen vehicles at the 8th hour of fermentation, with a lysine yield of 208.36 g/L and a conversion rate of 83.3%. In addition, n-dodecane significantly reduced the amount of foam produced during fermentation, which is beneficial for fermentation control and equipment. The new oxygen-enhanced bioreactor improves oxygen transfer efficiency, and oxygen vectors enhance the ability of cells to take up oxygen, which effectively solves the problem of insufficient oxygen supply during lysine fermentation. This study provides a new bioreactor and production solution for lysine fermentation.
L-赖氨酸是一种大宗产品。在采用高生物量发酵的工业生产中，细菌的高密度和生产强度需要足够的细胞呼吸代谢来支持。传统生物反应器往往难以满足这种发酵过程的氧气供应条件，不利于提高糖-氨基酸转化率。在本研究中，我们设计并开发了一种富氧生物反应器来解决这一问题。该生物反应器使用内部液体导流装置和多个螺旋桨优化曝气混合。与传统生物反应器相比，它将ka从367.57提高到875.64 h，提高了238.22%。结果表明，富氧生物反应器的氧气供应能力优于传统生物反应器。其充氧效果使发酵中后期的溶解氧平均增加了20%。LS260在生长中后期活力的提高导致L-赖氨酸产量达到185.3 g/L，赖氨酸从葡萄糖的转化率为74.57%，生产效率为2.57 g/L/h，分别比传统生物反应器提高了11.0%、6.01%和8.2%。氧载体可以通过提高微生物的吸氧能力进一步提高赖氨酸菌株的生产性能。我们比较了不同氧载体对LS260发酵生产L-赖氨酸的影响，得出正十二烷是最合适的。在这些条件下细菌生长更平稳，细菌体积增加2.78%，赖氨酸产量增加6.53%，转化率增加5.83%。氧载体的不同添加时间也影响最终产量和转化率，与不添加氧载体的发酵相比，在发酵0 h、8 h、16 h和24 h添加氧载体，产量分别提高6.31%、12.44%、9.93%和7.39%。转化率分别提高5.83%、8.73%、7.13%和6.13%。在发酵第8小时添加氧载体效果最佳，赖氨酸产量为208.36 g/L，转化率为83.3%。此外，正十二烷显著减少了发酵过程中产生的泡沫量，这有利于发酵控制和设备运行。新型富氧生物反应器提高了氧传递效率，氧载体增强了细胞吸氧能力，有效解决了赖氨酸发酵过程中氧气供应不足的问题。本研究为赖氨酸发酵提供了一种新型生物反应器和生产解决方案。
