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Modifications to the Bacterial Cell Envelope Increase Lipid Production
Published: May 23, 2017
Posted: July 14, 2017

A new strategy significantly increases the production and secretion of microbial lipids in bacteria that can be grown at industrial scale.

The Science
High-yield microbial production of lipids presents a significant challenge, often falling short of what can be theoretically obtained. This study characterized high-lipid (HL) mutant variants of Rhodobacter sphaeroides and showed that alterations to the bacterial cell envelope can result in increased accumulation of lipids relative to the parent strain.

The Impact
Knowledge of the mechanisms that limit microbial lipid production can reveal new strategies to increase lipid yield and the economic viability of alternatives to fuels or chemicals currently derived from petroleum.

Summary
Microbial lipids are potential replacements for petroleum-based fuels and chemicals; however, their production often falls short of theoretical yield, and improvement strategies are needed. Researchers from the Department of Energy’s (DOE) Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, and Environmental Molecular Sciences Laboratory (EMSL; a DOE Office of Science user facility) advanced their research on microbial lipid production by examining a new class of Rhodobacter sphaeroides mutants that exhibited enhanced lipid accumulation relative to the parent strain. The researchers used EMSL’s FEI Tecnai T-12 cryo-transmission electron microscope and structured illumination super resolution fluorescence microscope, in which chemical sensitivity profiles indicated HL mutants were sensitive to drugs that target the cell envelope. Changes in cell shape were also observed, suggesting that previously undescribed alterations in the bacterial cell envelope could be used to increase bacterial lipid production. Importantly, a subset of the HL mutants were able to secrete lipids, two of which accumulated approximately 60 percent of their total lipids extracellularly, potentially enabling easy product recovery from a bioreactor. When one of the highest lipid-secreting strains was grown in a fed-batch bioreactor, its lipid content was comparable to oleaginous microbes, defined as those accumulating 20 percent or more of their dry cell weight as lipid. Knowledge of the biological mechanisms that limit lipid production can inform new genetic engineering and growth strategies and enable this important class of molecules to be adopted as fuels or chemicals on a larger scale.

BER PM Contacts
Paul Bayer, SC-23.1, 301-903-5324
Kent Peters, SC-23.2, 301-903-5549

PI Contact
Timothy J. Donohue
University of Wisconsin-Madison
tdonohue@bact.wisc.edu

EMSL Contacts
Alice Dohnalkova
EMSL
Alice.Dohnalkova@pnnl.gov

Dehong Hu
EMSL
Dehong.Hu@pnnl.gov

Galya Orr
EMSL
Galya.Orr@pnnl.gov

Funding
This work was supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, including support of the Environmental Molecular Sciences Laboratory and Great Lakes Bioenergy Research Center.

Publication
Lemmer, K. C., W. Zhang, S. J. Langer, A. C. Dohnalkova, D. Hu, R. A. Lemke, J. S. Piotrowski, G. Orr, D. R. Noguera, and T. J. Donohue. 2017. “Mutations That Alter the Bacterial Cell Envelope Increase Lipid Production,” mBio 8(3), e00513-17. DOI: 10.1128/mbio.00513-17. (Reference link)

Related Links
Modifications to the Bacterial Cell Envelope Increase Lipid Production, EMSL science highlight
Modifying Cell Wall Can Increase Bacterial Lipids, Great Lakes Bioenergy Research Center highlight
Lipid Biofuels EMSL science highlight
Enhancing Microbial Lipid Production, Great Lakes Bioenergy Research Center highlight

Topic Areas:

  • Research Area: DOE Environmental Molecular Sciences Laboratory (EMSL)
  • Research Area: Microbes and Communities
  • Research Area: DOE Bioenergy Research Centers (BRC)
  • Research Area: Biological Engineering
  • Research Area: Structural Biology
  • Mission Science: Sustainable Biofuels

Division: SC-23.2 Biological Systems Science Division, BER

 

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