Tuesday, April 30, 2013
Exhibit Hall
The advancement of fermentative ethanol production has focused on the development of technologies capable of utilising the lignocellulosic fraction of biomass, abundant in the structural components of plants. These second-generation technologies are based on fermentation by metabolically-engineered organisms that are capable of utilising a wide range of substrates. The thermophile, Geobacillus thermoglucosidasius, is capable of producing ethanol from substrates including hexose and pentose sugars, as well as some complex polycarbohydrates. A UK based company, TMO Renewables Ltd, has demonstrated that an engineered form of G. thermoglucosidasius is capable of efficiently and rapidly producing ethanol in yields in excess of 90% of theoretical. However, small but significant quantities of certain organic acids, particularly acetate, are produced when grown under fermentation conditions.
The current project aims to study the metabolic flux of this strain, in particular the formation of acetate from acetyl-CoA in relation to ethanol production, in order to increase ethanol yields by further genetic manipulations. Acetate formation is a result of the action of phosphotransacetylase (PTA) and acetate kinase (AcK), which convert acetyl-CoA to acetate via an acetyl-phosphate intermediate. This report describes the creation and characterisation of a Geobacillus strain in which the pta gene has been deleted in order to divert metabolic flux away from acetate, towards ethanol production. Upon characterisation of this strain a novel acetate producing pathway based on enzyme promiscuity has been discovered.