Successful scale-up of bioprocesses requires that laboratory-scale performance is equally achieved during large-scale production to meet economic constraints. In industry, heuristic approaches are often applied, making use of physical scale-up criteria that do not consider cellular needs or properties. As a consequence, large-scale productivities, conversion yields, or product purities are often deteriorated, which may prevent economic success. The occurrence of population heterogeneity in large-scale production may be the reason for underperformance. In this study, an in silico method to predict the formation of population heterogeneity by combining computational fluid dynamics (CFD) with a cell cycle model of Pseudomonas putida KT2440 was developed. The glucose gradient and flow field of a 54,000 L stirred tank reactor were generated with the Euler approach, and bacterial movement was simulated as Lagrange particles. The latter were statistically evaluated using a cell cycle model. Accordingly, 72% of all cells were found to switch between standard and multifork replication, and 10% were likely to undergo massive, transcriptional adaptations to respond to extracellular starving conditions. At the same time, 56% of all cells replicated very fast, with µ ≥ 0.3 h−1 performing multifork replication. The population showed very strong heterogeneity, as indicated by the observation that 52.9% showed higher than average adenosine triphosphate (ATP) maintenance demands (12.2%, up to 1.5 fold). These results underline the potential of CFD linked to structured cell cycle models for predicting large-scale heterogeneity in silico and ab initio.
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机译:成功地扩大生物过程规模需要在大规模生产期间均等地达到实验室规模的性能,以满足经济上的限制。在工业中,经常采用启发式方法,利用不考虑细胞需求或特性的物理放大标准。结果,大规模的生产率,转化率或产品纯度经常恶化,这可能阻止经济上的成功。大规模生产中人口异质性的发生可能是业绩不佳的原因。在这项研究中,开发了一种计算机模拟方法,通过结合计算流体动力学(CFD)和恶臭假单胞菌KT2440的细胞周期模型来预测种群异质性的形成。通过Euler方法生成了54,000 L搅拌釜反应器的葡萄糖梯度和流场,并将细菌运动模拟为拉格朗日粒子。使用细胞周期模型对后者进行统计学评估。因此,发现所有细胞中有72%在标准和多叉复制之间进行切换,而10%的细胞可能会经历大规模的转录适应,以响应细胞外饥饿的状况。同时,所有细胞中有56%的细胞复制非常快,其中µ≥0.3 h -1 sup>进行多叉复制。该群体显示出非常强的异质性,观察到的结果是52.9%的人显示出高于平均三磷酸腺苷(ATP)维持需求(12.2%,高达1.5倍)。这些结果强调了CFD与结构化细胞周期模型相关联的潜力,可用于预测硅和从头算起的大规模异质性。
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