Rice: Unconventional Wisdom
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Metabolic Engineering and Synthetic & Systems Biology Laboratory

Microbial platforms for the production of chemicals and fuels from glycerol

 

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The oil platform is one of the main three platforms envisioned for the production of biofuels. Its goal is to first extract the oil portion of an oil-accumulating plant (e.g., soybean or rapeseed) and then either use this oil to produce biodiesel (a mixture of fatty acid methyl esters) or process it into bio-distillates via conventional refinery technology. The rapidly growing biodiesel industry, however, is flooding US and international markets with glycerol, a significant co-product of both biodiesel and oleochemical production. For this reason, research into the conversion of glycerin into other useful products has the potential to revolutionize this industry and dramatically improve its economics.

The need for obtaining new chemicals from glycerol is such that U.S. government agencies such as the Department of Energy have as one of their main goals to promote the development of new glycerol platform chemistry and product families. Not only is glycerol cheap and abundant but the higher reduced state of carbon in glycerol (compared to cellulosic sugars) has the potential to significantly increase the yield of chemicals whose production from these sugars is limited by the availability of reducing equivalents. Realizing this potential, however, would require the use of microorganisms able to perform glycerol fermentation in the absence of electron acceptors. However, the ability to ferment glycerol is restricted to very few organisms, most of them not amenable to industrial applications. For example, it has been though for more than 80 years that E. coli (the workhorse of modern biotechnology) is unable to fermentatively metabolize glycerol. However, we recently discovered that this organism is in fact able to metabolize glycerol in a purely fermentative way.

Our current work focuses in two directions: (1) elucidating the pathways and mechanisms mediating the anaerobic fermentation of glycerol in E. coli and other Enteric bacteria, and (2) engineering these organisms for the production of fuels and chemicals from glycerol. In both cases we take advantage of the expertise we have developed on the use of functional genomics and systems biology tools.