Increased Production of Bioplastics in Engineered Bacteria
Metabolic engineering doubles the production of ethylene in Escherichia coli.
Researchers analyzed growth media and nutrient supplements to identify candidate genes that affect yields in an engineered E. coli strain that produces ethylene, a hydrocarbon used in the production of a wide range of chemicals and plastics. Guided by the results of those analyses, the researchers further engineered the bacterial strain, altering several metabolic and regulatory genes to more than double the original ethylene production levels.
Ethylene is currently derived from fossil fuels through an energy-intensive process called steam cracking. The production of plastics and many other products and chemicals creates huge demand for ethylene, so biological production of ethylene has great potential to reduce the industry’s carbon footprint. Ethylene biosynthesis has been engineered in microbial systems, but with low yields. The identification and engineering of selected E. coli metabolic and regulatory genes in this research has resulted in a substantial increase in ethylene yield, advancing the sustainable bioproduction of this critical hydrocarbon.
Ethylene is one of the most industrially important chemicals derived from petroleum. Therefore, scientists have been trying to develop biological systems to produce ethylene in a sustainable way. Expression of a heterologous bacterial ethylene-forming enzyme (EFE) in E. coli has resulted in the production of ethylene, but the yields were too low for industrial purposes. Researchers at the National Renewable Energy Laboratory and University of Colorado Boulder conducted a study of the effects of different nutrients and substrates present in the growth medium for the EFE-expressing E. coli strain to be able to predict which genes significantly affect ethylene yields. Guided by those findings, they re-engineered E. coli to minimize competing pathways within central metabolism and to overproduce key enzymes predicted to increase ethylene productivity. The re-engineered strain produced more than twice as much ethylene relative to the original EFE-expressing E. coli strain. Those yields can be further improved by identifying and engineering additional enzymes and regulatory factors that prevent higher metabolic flow toward ethylene biosynthesis. This work advances the development of a sustainable ethylene production industry that is not dependent on fossil fuels.
National Renewable Energy Laboratory
This work was supported by the Office of Biological and Environmental Research within the U.S. Department of Energy’s Office of Science under award DE-SC008812.
Lynch, S., C. Eckert, J. Yu, R. Gill, and P. C. Maness. 2016. “Overcoming Substrate Limitations for Improved Production of Ethylene in E. coli,” Biotechnology for Biofuels 9:3. DOI: 10.1186/s13068-015-0413-x.