Conversion of proteins into biofuels by engineering nitrogen flux

• Published in: Nature biotechnology Vol. 29; no. 4; pp. 346 - 351
• Main Authors: Liao, James C, Huo, Yi-Xin, Cho, Kwang Myung, Rivera, Jimmy G Lafontaine, Monte, Emma, Shen, Claire R, Yan, Yajun
• Format: Journal Article
• Language: English
• Published: New York, NY Nature Publishing Group 01.04.2011
• Subjects: Alcohols - metabolism; Amino Acids - metabolism; Bacillus subtilis - growth & development; Bacillus subtilis - metabolism; Bacterial Proteins - metabolism; Biodiesel fuels; Biofuel production; Biofuels; Biological and medical sciences; Biomass; Biomass energy; Biosynthesis; Biotechnology; Butanols - metabolism; Deamination; E coli; Energy; Escherichia coli - growth & development; Escherichia coli - metabolism; Fermentation; Fundamental and applied biological sciences. Psychology; Genetic Testing; Industrial applications and implications. Economical aspects; Microalgae - metabolism; Mutation; Nitrogen - metabolism; Plasmids; Properties; Protein Engineering - methods; Protein hydrolysates; Proteins; Proteins - metabolism; Saccharomyces cerevisiae - growth & development; Saccharomyces cerevisiae - metabolism; United States; Deamination; Escherichia coli; Production; Bacteria; Metabolic engineering; Biofuel; Biorefinery; Nitrogen; Protein; Enterobacteriaceae
• ISSN: 1087-0156; 1546-1696
• DOI: 10.1038/nbt.1789

Biofuels are currently produced from carbohydrates and lipids in feedstock. Proteins, in contrast, have not been used to synthesize fuels because of the difficulties of deaminating protein hydrolysates. Here we apply metabolic engineering to generate Escherichia coli that can deaminate protein hydrolysates, enabling the cells to convert proteins to C4 and C5 alcohols at 56% of the theoretical yield. We accomplish this by introducing three exogenous transamination and deamination cycles, which provide an irreversible metabolic force that drives deamination reactions to completion. We show that Saccharomyces cerevisiae, E. coli, Bacillus subtilis and microalgae can be used as protein sources, producing up to 4,035 mg/l of alcohols from biomass containing ∼22 g/l of amino acids. These results show the feasibility of using proteins for biorefineries, for which high-protein microalgae could be used as a feedstock with a possibility of maximizing algal growth and total CO2 fixation.