Department of Bioscience and Bioengineering, Dalian University of Technology, Dalian 116024, China.
Biotechnol Bioeng. 2010 Apr 1;105(5):935-44. doi: 10.1002/bit.22610.
Taking continuous ethanol fermentation with the self-flocculating yeast SPSC01 under very high concentration conditions as an example, the fermentation performance of the yeast flocs and their metabolic flux distribution were investigated by controlling their average sizes at 100, 200, and 300 microm using the focused beam reflectance online measurement system. In addition, the impact of zinc supplementation was evaluated for the yeast flocs at the size of 300 microm grown in presence or absence of 0.05 g L(-1) zinc sulfate. Among the yeast flocs with different sizes, the group with the average size of 300 microm exhibited highest ethanol production (110.0 g L(-1)) and glucose uptake rate (286.69 C mmol L(-1) h(-1)), which are in accordance with the increased flux from pyruvate to ethanol and decreased flux to glycerol. And in the meantime, zinc supplementation further increased ethanol production and cell viability comparing with the control. Zinc addition enhanced the carbon fluxes to the biosynthesis of ergosterol (28.6%) and trehalose (43.3%), whereas the fluxes towards glycerol, protein biosynthesis, and tricarboxylic acid cycle significantly decreased by 37.7%, 19.5%, and 27.8%, respectively. This work presents the first report on the regulation of metabolic flux by the size of yeast flocs and zinc supplementation, which provides the potential for developing engineering strategy to optimize the fermentation system.
以高浓度条件下自絮凝酵母 SPSC01 的连续乙醇发酵为例，使用聚焦光束反射在线测量系统将酵母絮体的平均粒径控制在 100、200 和 300μm，研究了酵母絮体的发酵性能及其代谢通量分布。此外，还评估了在添加或不添加 0.05g/L 硫酸锌的情况下，粒径为 300μm 的酵母絮体中锌的补充作用。在不同粒径的酵母絮体中，平均粒径为 300μm 的酵母絮体表现出最高的乙醇产量（110.0g/L）和葡萄糖摄取率（286.69Cmmol/L/h），这与从丙酮酸到乙醇的通量增加和到甘油的通量减少相一致。同时，与对照组相比，锌的添加进一步提高了乙醇产量和细胞活力。锌的添加增强了碳通量向麦角固醇（28.6%）和海藻糖（43.3%）的生物合成，而甘油、蛋白质生物合成和三羧酸循环的通量分别显著降低了 37.7%、19.5%和 27.8%。本研究首次报道了酵母絮体大小和锌补充对代谢通量的调节作用，为优化发酵系统的工程策略提供了潜力。
