Although biofuels such as biodiesel and bioethanol represent a sustainable, secure, renewable, and environmentally safe alternative to fossil fuels, major scientific and technological breakthroughs are needed for them to become economically viable. The long-term goals of the proposed research are to elucidate the pathways and mechanisms mediating the anaerobic fermentation of glycerol in E. coli and use the knowledge base thus created to engineer this organism for the efficient production of reduced chemicals and fuels. The specific objectives of the research plan are: (1) study the effect of medium composition and cultivation conditions on glycerol fermentation, (2) assess the role of hypothesized pathways in the fermentative metabolism of glycerol by using genetic and biochemical approaches; (3) identify genes, proteins, and metabolic processes involved in the fermentation of glycerol using functional genomics tools; and (4) engineer E. coli for the efficient co-production of ethanol and hydrogen, thus illustrating the advantages of using glycerol fermentation as a new platform to produce biofuels and biochemicals. To achieve these goals, functional genomics tools will be used to supplement a traditional hypothesis-driven approach. In addition, metabolic engineering will be used as a rational approach to engineer E. coli for the conversion of glycerol into ethanol and hydrogen. The intellectual merit of this proposal relates to elucidating the fermentative metabolism of glycerol in E. coli, a puzzle that has remained unresolved for more than eighty years. By enabling and integrating the production of biofuels, this proposal will contribute to the creation of fundamentally new processes and paradigms such as those embracing the biorefinery concept. This research will also make significant contributions to the education of our society on the role of biofuels as enablers of a secure and sustainable energy future.
In 2006 our laboratory discovered that the bacterium Escherichia coli can anaerobically ferment glycerol, a previously unknown metabolic capability of this organism. This fundamental discovery laid the foundation for the development of a platform of technologies to convert glycerol to higher-value products, thus establishing a new path to the production of biofuels and biochemicals. Given the worldwide surplus of crude glycerol generated as inevitable by-product of biofuel production, our findings have the potential to dramatically improve the economics of the biofuel industry. This NSF CAREER project elucidated the pathways and mechanisms mediating the anaerobic fermentation of glycerol in E. coli and used the knowledge base thus created to engineer this organism for the efficient production of reduced chemicals and fuels. More specifically, we studied the effect of medium composition and cultivation conditions on glycerol fermentation, thus identifying specific environments that promote or impair this process; assessed the role of hypothesized pathways in the fermentative metabolism of glycerol by using genetic and biochemical approaches; identified genes, proteins, and metabolic processes involved in the fermentation of glycerol using functional genomics tools; and engineered E. coli for the efficient co-production of ethanol & H2. We also made significant contributions to the education of our society on the role of biofuels as enablers of a secure and sustainable energy future. Specifically, we promoted awareness and education on the role of biofuels in transforming our energy future; motivated interest and educated middle and high school students, particularly those from underrepresented minority groups, in the topic of biofuels; developed and implemented innovative graduate and undergraduate courses related to the production of biofuels and biochemicals; and encouraged a career in the area of alternative energy.
