UC Berkeley

Metabolism represents at least three and a half billion years of research and development in chemical synthesis and degradation. Human have been taking advantage of this resource for thousands of years, first with the advent of agriculture and the invention of cheese, beer and other fermentation products. More recently selective breeding, metabolic engineering and synthetic biology have given humanity more control over organisms’ metabolism, enabling food, chemical and fuel production on massive scales. Given the extensive previous work optimize existing metabolism to make products, the two most exciting frontiers for metabolic engineering are 1) making new chemicals and 2) making old chemicals with new and improved pathways. To explore the area of new chemical production, we have heterologously expressed the lepidopteran mevalonate pathway in Escherichia coli to make sixteen carbon homoterpenes. Because the pathway is modular, we demonstrate that making novel homoterpenes requires only altering one gene. As terpenes are an economically valuable class of molecules, we hope that this pathway will enable the exploration of new chemical space difficult to search with traditional organic synthesis techniques. To explore the area of new pathways we designed a pathway to make the five-carbon alcohols prenol and isopentanol. While there are already pathways to five-carbon alcohols, the novel pathway does not require ATP. In fact, if glucose is the carbon source, the pathway is ATP positive when redox balanced with non-oxidative glycolysis. Because of this it is theoretically possible to ferment these five carbon alcohols the same way microbes ferment ethanol, potentially easing many engineering problems around titer improvements and scaling to industrial production levels. Finally, the challenges of CO2 emissions will be considered. Many technologies will need to be developed to sustain a prosperous global society. While some of these technologies will be based in traditional engineering fields, biology and metabolism offer unique opportunities and will be critical to enabling a CO2 neutral civilization in the future.