P112: Understanding the fermentative utilization of glycerol and its application for the production of fuels and reduced chemicals

Given the need to develop technologies capable of producing fuels and chemicals from the wide array of available feedstock constituents, glycerol, a readily available and inexpensive constituent, offers the advantage of enabling higher yields of fuels and reduced chemicals when compared to the use of carbohydrate based feedstocks.  However, the reduced nature of carbon atoms in glycerol facilitating this advantage also results in significant challenges, as several cellular processes enabling key fermentative functions require different mechanisms during fermentative glycerol utilization that those associated with traditional carbon sources.  Therefore unlocking the full potential of microorganisms for the conversion of glycerol into fuels and chemicals requires a more detailed understanding of fermentative glycerol metabolism.

The work presented here highlights a comprehensive experimental investigation into the fermentative utilization of glycerol by Escherichia coli, which has elucidated several key pathways and mechanisms including the activity of both the fermentative and respiratory glycerol dissimilation pathways, the involvement of several FBPases for the production of 6-carbon intermediates, and the CRP-cAMP regulation of the fermentative glycerol dissimilation pathway.  Of central influence to many of these findings is the metabolic cycle created by the coupling of glycerol dissimilation with pyruvate synthesis through the action of PEP-dependent dihydroxyacetone kinase.  Using this improved understanding of fermentative glycerol metabolism as a platform, E. coli has been engineered to produce high yields and titers of ethanol (19.8 g/L, 0.46 g/g) and 1,2-propanediol (5.6 g/L, 0.21 g/g) from glycerol, demonstrating its potential as a carbon source for the production of fuels and chemicals.