Influence of load-induced morphological changes on the productivity of the filamentous pellet system Actinomadura namibiensis

丝状微生物是许多用于生产药物化合物、抗生素、蛋白质和有机酸的工业生物技术过程的核心。这些微生物通常在搅拌罐或摇瓶中培养为分散的菌丝体或颗粒。颗粒状微生物的特征性质是颗粒形态与颗粒生长和生产率之间的紧密联系。特别是，颗粒内细丝的分布控制内部质量传输，这反过来又影响颗粒芯中细丝的生存力并决定潜在的底物限制。虽然形态对于颗粒的生存力和生产率至关重要，但过去的实验研究表明，形态主要由培养条件和颗粒所经历的机械负荷塑造。在单个颗粒的水平上，机械载荷、形态和生产率之间的强烈相互作用构成了我们研究项目的核心。基于动力学表达式的机械力施加在一个颗粒，形态和颗粒代谢的变化率，我们的目标是概念化和开发一个物理模型的前所未有的保真度的分析和预测的产品产量在造粒，浸没式培养。然而，新的模型可以部署到推断反应器的设计，搅拌和操作的指导方针，以达到最佳的功耗，培养时间和产品产量。这与现有的模型形成鲜明对比，现有的模型仅限于特定的反应器配置和操作条件，并且忽略了分散颗粒的负载引起的形态变化。在所提出的模型的范围内，我们结合联合收割机的颗粒人口在一个完美的搅拌反应器中的流动分辨的测定颗粒特定的负载集体在很短的时间尺度上的长时间的描述，从而桥接特征混合和培养时间之间的广泛的尺度。纳米比亚马杜拉放线菌（Actinomadura namibiensis）原核生物可作为丝状模式生物，因为它适合在摇瓶中进行实验室规模培养，并产生肽类抗生素Labelothopeptin A1。为了校准和验证所提出的模型，我们计划一个双轨实验活动。一方面，记录摇瓶中底物和产物浓度的时间变化以及整个颗粒群的形态分布沿着。另一方面，进行颗粒特定实验，用于分析渗透性、内部氧分布和机械刚度。

Filamentous microorganisms are central to many industrial biotechnological processes for the production of pharmaceutical compounds, antibiotics, proteins and organic acids. These microorganisms are commonly cultivated in stirred tanks or shaking flasks either as dispersed mycelia or pellets. A characteristic property of pelleted microorganisms is the tight connection between the pellet morphology and the pellet growth and productivity. In particular, the distribution of filaments within a pellet controls the internal mass transport which, in turn, affects the viability of filaments in the pellet core and determines potentional substrate limitations. While the morphology is vital for the viability and productivity of the pellets, past experimental investigations have shown that the morphology is predominantly shaped by the cultivation conditions and the mechanical loads experienced by the pellets. The strong interactions between mechanical loads, morphology and productivity on the level of a single pellet constitute the core of our research project. Based on kinetic expressions for the mechanical forces exerted on a pellet, the rate of change of morphology and the pellet metabolism, our objective is to conceptualise and develop a physical model of unprecedented fidelity for the analysis and prediction of the product yield in pelleted, submerged cultures. Perspectively, the novel model may be deployed to infer guidelines on reactor design, agitation and operation, targeting an optimum of power consumption, cultivation duration and product yield. This is in sharp contrast to existing models which are restricted to particular reactor configurations and operating conditions and in which load-induced morphological changes of the dispersed pellets are neglected. Within the scope of the proposed model, we combine a long-time description of pellet populations in a perfectly stirred reactor with the flow-resolved determination of pellet-specific load collectives on very short time scales, thus bridging the wide range of scales between characteristic mixing and cultivation times. The procaryot Actinomadura namibiensis serves as filamentous model organism as it is amenable to lab-scale cultivation in shaking flasks and produces the peptid antibiotic Labyrinthopeptin A1. In order to calibrate and validate the proposed model, we plan a two-track experimental campaign. On the one hand, the temporal changes of the substrate and product concentrations in the shaking flask are recorded along with the morphology distribution across the pellet population. On the other hand, pellet-specific experiments for the analysis of permeability, internal oxygen distribution and mechanical stiffness are undertaken.