(67e) Dynamic Flux Balance Modeling of a Microbial Co-Culture for Efficient Batch Fermentation of Glucose and Xylose Mixtures

A requirement for the economically viable production of fuels from cellulosic biomass is the efficient consumption and conversion of its constituent sugars. Genetically engineering a single organism to metabolize multiple sugars typically results in inefficiencies due to diauxic growth or limitations in substrate uptake. Here, we present a model of a synthetic consortium for the production of ethanol composed of wild-type Saccharomyces cerevisiae and Escherichia coli strain ZSC113, two microbes that will specifically uptake glucose and xylose respectively. Dynamic flux balance analysis is employed to compare this co-culture to mono-cultures of the strains of the component microbes capable of consuming both sugars in terms of ethanol productivity. The effects of altering the amount of each microbe present in reactor inoculum and changing the time at which the batch is switched from aerobic to anaerobic cultivation are investigated. Through these process engineering strategies, a nearly two-fold increase in ethanol productivity over pure cultures in silico is achieved. Future work will focus on verifying these results experimentally to test the validity of assumptions made in our model.