1 Department of Energy, Environmental, and Chemical Engineering, Washington University in St. Louis, St. Louis, MO, USA. Electronic address: joshua.yuan@wustl.edu.
2 Editor, Trends in Biotechnology. Electronic address: mpavlovich@cell.com.
3 Department of Forestry, Wildlife, and Fisheries, Center for Renewable Carbon, University of Tennessee Institute of Agriculture, Knoxville, TN 37996, USA; Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, TN 37996, USA.
4 Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.