Chair of Bioprocess Engineering, Department of Biotechnology, Technische Universität Berlin, Berlin, Germany.
Biotechnol J. 2011 Aug;6(8):1009-17. doi: 10.1002/biot.201100293.
This study describes an advanced version of a two-compartment scale-down bioreactor that simulates inhomogeneities present in large-scale industrial bioreactors on the laboratory scale. The system is made of commercially available parts and is suitable for sterilization with steam. The scale-down bioreactor consists of a usual stirred tank bioreactor (STR) and a plug flow reactor (PFR) equipped with static mixer modules. The PFR module with a working volume of 1.2 L is equipped with five sample ports, and pH and dissolved oxygen (DO) sensors. The concept was applied using the non-sporulating Bacillus subtilis mutant strain AS3, characterized by a SpoIIGA gene knockout. In a fed-batch process with a constant feed rate, it is found that oscillating substrate and DO concentration led to diminished glucose uptake, ethanol formation and an altered amino acid synthesis. Sampling at the PFR module allowed the detection of dynamics at different concentrations of intermediates, such as pyruvic acid, lactic acid and amino acids. Results indicate that the carbon flux at excess glucose and low DO concentrations is shifted towards ethanol formation. As a result, the reduced carbon flux entering the tricarboxylic acid cycle is not sufficient to support amino acid synthesis following the oxaloacetic acid branch point.
本研究描述了一种两室比例缩小生物反应器的高级版本，该生物反应器可在实验室规模上模拟大型工业生物反应器中的不均匀性。该系统由市售部件组成，适合蒸汽灭菌。比例缩小生物反应器由常规搅拌槽生物反应器（STR）和带有静态混合器模块的推流反应器（PFR）组成。工作容积为 1.2 L 的 PFR 模块配备了五个样品端口、pH 和溶解氧（DO）传感器。该概念应用于不产孢子的枯草芽孢杆菌突变株 AS3，其特征是 SpoIIGA 基因敲除。在恒速进料的分批补料过程中，发现振荡的基质和 DO 浓度导致葡萄糖摄取、乙醇形成和氨基酸合成减少。在 PFR 模块采样可检测到不同浓度中间产物（如丙酮酸、乳酸和氨基酸）的动态变化。结果表明，在过量葡萄糖和低 DO 浓度下，碳通量向乙醇形成转移。因此，进入三羧酸循环的减少的碳通量不足以支持草酰乙酸分支点后氨基酸的合成。
