Department of Biotechnology, Delft University of Technology, Delft, The Netherlands.
Biotechnol Bioeng. 2021 Apr;118(4):1576-1586. doi: 10.1002/bit.27672. Epub 2021 Jan 21.
This study explores the relation between biomass-specific succinic acid (SA) production rate and specific growth rate of an engineered industrial strain of Saccharomyces cerevisiae, with the aim to investigate the extent to which growth and product formation can be uncoupled. Ammonium-limited aerobic chemostat and retentostat cultures were grown at different specific growth rates under industrially relevant conditions, that is, at a culture pH of 3 and with sparging of a 1:1 CO -air mixture. Biomass-specific SA production rates decreased asymptotically with decreasing growth rate. At near-zero growth rates, the engineered strain maintained a stable biomass-specific SA production rate for over 500 h, with a SA yield on glucose of 0.61 mol mol . These results demonstrate that uncoupling of growth and SA production could indeed be achieved. A linear relation between the biomass-specific SA production rate and glucose consumption rate indicated the coupling of SA production rate and the flux through primary metabolism. The low culture pH resulted in an increased death rate, which was lowest at near-zero growth rates. Nevertheless, a significant amount of non-viable biomass accumulated in the retentostat cultures, thus underlining the importance of improving low-pH tolerance in further strain development for industrial SA production with S. cerevisiae.
本研究探讨了生物质特异性琥珀酸（SA）生产速率与酿酒酵母工程工业菌株比生长速率之间的关系，旨在研究生长和产物形成解耦的程度。在工业相关条件下，即在 pH 值为 3 和以 1:1 的 CO-空气混合物鼓泡的条件下，在不同比生长速率下进行了铵限制好氧恒化器和恒化器培养。生物质特异性 SA 生产速率随生长速率的降低而渐近降低。在接近零生长速率下，该工程菌株在超过 500 小时的时间内保持稳定的生物质特异性 SA 生产速率，葡萄糖的 SA 得率为 0.61 mol/mol。这些结果表明确实可以实现生长和 SA 生产的解耦。生物质特异性 SA 生产速率与葡萄糖消耗速率之间的线性关系表明 SA 生产速率与初级代谢通量偶联。低培养 pH 值导致死亡率增加，在接近零生长速率时最低。然而，在恒化器培养物中积累了大量的非存活生物质，因此强调了在进一步的菌株开发中提高耐低 pH 值的重要性，以用于酿酒酵母的工业 SA 生产。
