Alpkvist Erik, Picioreanu Cristian, van Loosdrecht Mark C M, Heyden Anders
Applied Mathematics Group, School of Technology and Society, Malmö University, Ostra/Stora Varvsgatan 11H, Malmö SE-205 06, Sweden.
Biotechnol Bioeng. 2006 Aug 5;94(5):961-79. doi: 10.1002/bit.20917.
An innovative type of biofilm model is derived by combining an individual description of microbial particles with a continuum representation of the biofilm matrix. This hybrid model retains the advantages of each approach, while providing a more realistic description of the temporal development of biofilm structure in two or three spatial dimensions. The general model derivation takes into account any possible number of soluble components. These are substrates and metabolic products, which diffuse and react in the biofilm within individual microbial cells. The cells grow, divide, and produce extracellular polymeric substances (EPS) in a multispecies model setting. The EPS matrix is described by a continuum representation as incompressible viscous fluid, which can expand and retract due to generation and consumption processes. The cells move due to a pushing mechanism between cells in colonies and by an advective mechanism supported by the EPS dynamics. Detachment of both cells and EPS follows a continuum approach, whereas cells attach in discrete events. Two case studies are presented for model illustration. Biofilm consolidation is explained by shrinking due to EPS and cell degradation processes. This mechanism describes formation of a denser layer of cells in the biofilm depth and occurrence of an irregularly shaped biofilm surface under nutrient limiting conditions. Micro-colony formation is investigated by growth of autotrophic microbial colonies in an EPS matrix produced by heterotrophic cells. Size and shape of colonies of ammonia and nitrite-oxidizing bacteria (NOB) are comparatively studied in a standard biofilm and in biofilms aerated from a membrane side.
一种创新型生物膜模型是通过将微生物颗粒的个体描述与生物膜基质的连续介质表示相结合而推导出来的。这种混合模型保留了每种方法的优点，同时在两个或三个空间维度上对生物膜结构的时间发展提供了更现实的描述。一般模型推导考虑了任何可能数量的可溶性成分。这些成分是底物和代谢产物，它们在生物膜内的单个微生物细胞中扩散并发生反应。在多物种模型设置中，细胞生长、分裂并产生细胞外聚合物（EPS）。EPS基质用连续介质表示为不可压缩粘性流体，由于生成和消耗过程，它可以膨胀和收缩。细胞通过菌落中细胞间的推动机制以及由EPS动力学支持的平流机制移动。细胞和EPS的脱离遵循连续介质方法，而细胞以离散事件附着。给出了两个案例研究用于模型说明。生物膜的巩固通过EPS和细胞降解过程导致的收缩来解释。该机制描述了生物膜深度处较致密细胞层的形成以及在营养限制条件下不规则形状生物膜表面的出现。通过自养微生物菌落在异养细胞产生的EPS基质中的生长来研究微菌落的形成。比较研究了标准生物膜以及从膜侧曝气的生物膜中氨氧化细菌和亚硝酸盐氧化细菌（NOB）菌落的大小和形状。
