State Key Laboratory of Microbial Metabolism, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
School of Information Science and Technology, Dalian Maritime University, Dalian, Liaoning 116023, China.
Biotechnol J. 2018 May;13(5):e1700697. doi: 10.1002/biot.201700697. Epub 2018 Jan 31.
Flocculation plays an important role in the immobilized fermentation of biofuels and biochemicals. It is essential to understand the flocculation phenomenon at physical and molecular scale; however, flocs cannot be studied directly due to fragile nature. Hence, the present study is focused on the morphological specificities of yeast flocs formation and sedimentation via the computer simulation by a single floc growth model, based on Diffusion-Limited Aggregation (DLA) model. The impact of shear force, adsorption, and cell propagation on porosity and floc size is systematically illustrated. Strong shear force and weak adsorption reduced floc size but have little impact on porosity. Besides, cell propagation concreted the compactness of flocs enabling them to gain a larger size. Later, a multiple flocs growth model is developed to explain sedimentation at various initial floc sizes. Both models exhibited qualitative agreements with available experimental data. By regulating the operation constraints during fermentation, the present study will lead to finding optimal conditions to control the floc size distribution for efficient fermentation and harvesting.
絮凝在生物燃料和生物化学的固定化发酵中起着重要作用。了解物理和分子尺度上的絮凝现象至关重要；然而，由于絮体的脆弱性质，无法直接研究絮体。因此，本研究通过基于扩散限制聚集（DLA）模型的单个絮体生长模型的计算机模拟，专注于酵母絮体形成和沉淀的形态特异性。系统地说明了剪切力、吸附和细胞繁殖对孔隙率和絮体尺寸的影响。强剪切力和弱吸附会减小絮体尺寸，但对孔隙率影响不大。此外，细胞繁殖使絮体更加紧密，从而使絮体获得更大的尺寸。之后，开发了一个多絮体生长模型来解释不同初始絮体尺寸下的沉淀。这两个模型与现有的实验数据定性一致。通过在发酵过程中调节操作条件，本研究将有助于找到控制絮体尺寸分布的最佳条件，以实现高效发酵和收获。
