Cellulosic ethanol is a biofuel that is produced from non-edible plants and plant materials, such as wood, switchgrass, and corn stover. It can have a positive net energy output with a reduction in green house gas emissions that is drastically lower than that of corn based ethanol and fossil fuels. Clostridium thermocellum is a bacteria that is able to directly convert cellulose into ethanol (and other by products). These bacteria colonize cellulose material and degrade cellulose by "chewing" their way through their substrate. In this talk we first present a very simple, spatially implicit reactor scale model for cellulose degradation by  C.thermocellum biofilms. The ODE can be studied with elementary techniques and quantitatively compared against experimental data. However, it does not allow for a detailed description of the spatial effects as the bacteria break down their substratum. To address this, we formulate then a spatially explicit model, which needs to incorporate volume filling effects. This leads to a highly degenrate diffusion-reaction equation for bacterial biomass that is coupled with an ordinary differential equation for the growth limiting substrate. We discuss briefly a numerical technique and compare computational simulations against experimental observations. Our simulations also suggest the existence of a traveling wave solution. To investigate this further we discuss two simplified versions of the model.

This is joint work with Eric Jalbert (Guelph), Alex Dumitrache (Oak Ridge National Labs), and Gideon Wolfaardt (Stellenbosch).

NOTE: This talk is presented jointyl with the Centre for Mathematical Medicine Seminar Series.