Cellulosic biomass is one of the most abundant industrial waste products and an appealing substrate for biorefining strategies to produce biofuels by fermentation. The metabolic engineering of fermentative bacteria, such as the thermophile Geobacillus thermoglucosidasius, for high bioethanol yield is well characterised. This has been traditionally facilitated by an economically inefficient multistep process referred to as separate hydrolysis and fermentation (SHF), in which the enzymatic hydrolysis of the cellulosic substrate and fermentation of the liberated sugars is performed sequentially.Consolidated bioprocessing (CBP) involves performing these two process steps simultaneously, by either introducing cellulolytic capabilities into naturally fermentative organisms or implementing fermentative capabilities in cellulolytic organisms through metabolic engineering. CBP is believed to be a potentially cost-efficient and commercially viable way to produce cellulosic biofuels since the feedback inhibition of glycosyl hydrolases by monosaccharides as they are released is reduced by their rapid conversion through microbial fermentation. This results in faster rates of production and higher yields than those possible with SHF. Furthermore, CBP offers energy savings by removing the need for a complex multistage process with multiple heating and cooling steps.The aim of the present project is the engineering of CBP capabilities in the ethanologen G. thermoglucosidasius through the heterologous secretion of active glycosyl hydrolases into the extracellular milieu or employing surface-layer homology domains to attach them to the bacterial cell-wall. Iterative optimisation will serve to evaluate the feasibility of CBP as a strategy for production of biofuels from lignocellulose using G. thermoglucosidasius.
|Date of Award||1 Apr 2016|
|Sponsors||Biotechnology and Biological Sciences Research Council|
|Supervisor||David Leak (Supervisor)|