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Conversion of proteins into biofuels by engineering nitrogen flux

Nature Biotechnology volume 29, pages 346–351 (2011)Cite this article

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Abstract

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 growth1 and total CO2 fixation.

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Figure 1: Screening of regulatory mutants for improved isobutanol production.
Figure 2: Nitrogen-centric metabolic engineering strategy in E. coli. Error bars indicate s.d. (n = 3).
Figure 3: Biofuel production and biorefining scheme from algal or bacterial protein sources.

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Acknowledgements

This work was partially supported by UCLA–Department of Energy Institute for Genomics and Proteomics.

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Authors and Affiliations

  1. Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, California, USA

    Yi-Xin Huo, Kwang Myung Cho, Jimmy G Lafontaine Rivera, Emma Monte, Claire R Shen, Yajun Yan & James C Liao

  2. Institute for Genomics and Proteomics, University of California, Los Angeles, Los Angeles, California, USA

    Kwang Myung Cho & James C Liao

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  1. Yi-Xin Huo
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Contributions

Y.-X.H. designed and performed experiments, designed the theoretical calculation, analyzed data and wrote the manuscript; K.M.C. designed and performed experiments and analyzed data; J.G.L.R. designed and performed theoretical calculation; E.M. performed part of the experiments in Table 1; C.R.S. performed the chemical mutagenesis; Y.Y. designed and performed carbon-flux driven biofuel production; J.C.L. designed experiments, theoretical calculation, analyzed data and wrote the manuscript.

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Correspondence to James C Liao.

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Competing interests

J.C.L. is a cofounder of Easel Biotechnoloiges, which licensed this technology from the University of California, Los Angeles.

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Supplementary Tables 1–7 and Supplementary Figs. 1–11 (PDF 2087 kb)

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Huo, YX., Cho, K., Rivera, J. et al. Conversion of proteins into biofuels by engineering nitrogen flux. Nat Biotechnol 29, 346–351 (2011). https://doi.org/10.1038/nbt.1789

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