Biosynthetic routes for renewable fuels and chemicals
Dr. Han Li
The Scripps Research Institute
The eventual replacement of fossil energy sources means that the fuels and chemicals must ultimately be produced from CO2, H2O, and sunlight. The work presented in the seminar will focus on engineering of the biocatalysts using synthetic biology tools to produce gasoline substitutes, pharmaceutical intermediates and industrial commodities from a variety of renewable feed stocks.
i) A synthetic pathway has been designed to produce homophenylalanine, a core pharmaceutical intermediate, in Escherichia coli by engineering the key enzymes in carbon chain elongation and amination using rational design and directed evolution. The carbon chain elongation platform demonstrated in this work could also be used to produce other non-native chemicals such as long chain alcohols. ii) Heterotrophic microbes such as E. coli utilize sugars as the feed stocks which are generated from plant biomass decomposition. To bypass plant biomass, photosynthetic chemical production was explored using the cyanobacterium Synechococcus elongatus. A synthetic pathway was installed in S. elongatus to produce 1,2-propanediol, an industrial commodity, directly from CO2. The pathway was further tailored to match the special metabolic features in the photosynthetic organism. iii) The photosynthetic microbial process faces challenges in scaling-up due to the requirement of the light exposure surface area. To achieve light independent fuel and chemical production from CO2, a lithoautotrophic microorganism Ralstonia eutropha was used. Metabolic engineering and electrochemical process design approaches were used to produce C4 and C5 alcohols, the gasoline substitutes, in an integrated electro-bioreactor using CO2 as the sole carbon source and electricity as the sole energy input.
Han Li did her undergraduate study in Tsinghua University, China, before she came to University of California, Los Angeles, for her PhD study in 2008. At UCLA, she joined Dr. James Liao’s group in Chemical & Biomolecular Engineering department, where she conducted research focusing on engineering of the biocatalysts to produce pharmaceutical intermediates, industrial commodities, and gasoline substitutes from renewable feed stocks. During her PhD study, Han Li co-authored more than 10 publications in Science, PNAS, ACS Chem Bio, ACS Synthetic Bio, and other peer-reviewed journals. Her major contributions include the first demonstration of biofuel production directly from CO2 and electricity. In 2013, Han Li joined Dr. Peter Schultz’s group at the Scripps Research Institute, La Jolla, where she is doing her postdoctoral study on synthetic DNA replication and protein translation systems in microorganisms.