†Department of Environmental Microbiology, UFZ - Helmholtz Centre for Environmental Research, Permoserstraße 15, 04318 Leipzig, Germany.
‡Institute of Groundwater Ecology, Helmholtz Zentrum München, Ingolstädter Landstr. 1, 85764 Neuherberg, Germany.
Environ Sci Technol. 2015 May 5;49(9):5529-37. doi: 10.1021/es505837v. Epub 2015 Apr 15.
Microbial degradation is an important process in many environments controlling for instance the cycling of nutrients or the biodegradation of contaminants. At high substrate concentrations toxic effects may inhibit the degradation process. Bioavailability limitations of a degradable substrate can therefore either improve the overall dynamics of degradation by softening the contaminant toxicity effects to microorganisms, or slow down the biodegradation by reducing the microbial access to the substrate. Many studies on biodegradation kinetics of a self-inhibitive substrate have mainly focused on physiological responses of the bacteria to substrate concentration levels without considering the substrate bioavailability limitations rising from different geophysical and geochemical dynamics at pore-scale. In this regard, the role of bioavailability effects on the kinetics of self-inhibiting substrates is poorly understood. In this study, we theoretically analyze this role and assess the interactions between self-inhibition and mass transfer-limitations using analytical/numerical solutions, and show the findings practical relevance for a simple model scenario. Although individually self-inhibition and mass-transfer limitations negatively impact biodegradation, their combined effect may enhance biodegradation rates above a concentration threshold. To our knowledge, this is the first theoretical study describing the cumulative effects of the two mechanisms together.
微生物降解是许多环境中的一个重要过程，例如控制营养物质的循环或污染物的生物降解。在高底物浓度下，毒性效应可能会抑制降解过程。因此，可生物降解底物的生物可利用性限制可以通过软化污染物对微生物的毒性效应来改善降解的整体动力学，或者通过减少微生物对底物的接触来减缓生物降解。许多关于自抑制底物生物降解动力学的研究主要集中在细菌对底物浓度水平的生理反应上，而没有考虑到由于孔隙尺度上不同的地球物理和地球化学动力学而引起的底物生物可利用性限制。在这方面，生物可利用性效应对自抑制底物动力学的作用知之甚少。在这项研究中，我们使用分析/数值解从理论上分析了这种作用，并评估了自抑制和传质限制之间的相互作用，展示了这些发现对于简单模型场景的实际意义。尽管自抑制和传质限制单独对生物降解有负面影响，但它们的组合效应可能会在浓度阈值以上提高生物降解速率。据我们所知，这是首次描述这两种机制共同累积效应的理论研究。
