Can synthetic biology and metabolic engineering contribute to the microbial production of lipids and oleochemicals?
Article first published online: 12 SEP 2011
Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
European Journal of Lipid Science and Technology
Volume 113, Issue 9, pages 1075–1076, September 2011
How to Cite
Bornscheuer, U. (2011), Can synthetic biology and metabolic engineering contribute to the microbial production of lipids and oleochemicals?. Eur. J. Lipid Sci. Technol., 113: 1075–1076. doi: 10.1002/ejlt.201100250
- Issue published online: 12 SEP 2011
- Article first published online: 12 SEP 2011
- Manuscript Accepted: 18 AUG 2011
- Manuscript Received: 12 AUG 2011
- Manuscript Revised: 12 AUG 2011
Vegetable (plant) oils are currently the key source of triglycerides necessary for human nutrition and animal feed. The majority of the annual world production of about 139 million metric tonnes is used for consumption and it is estimated that about 20% serve as starting material for oleochemistry or are converted into biodiesel fuels 1. However, depletion of fossil oil resources forces the chemical industry to find replacements for petrol as raw material, biofuels are increasingly used and at the same time the growing world population requires more supply with fats and oils. Consequently, their production must be increased ensuring at the same time affordable prices, especially for human nutrition. An increase of the agricultural area for plant oil production is hampered by the lack of arable land available and the average increase in productivity (tons of oil per hectare) is only very small. The use of algal oils has been suggested as an alternative, which is however highly questionable for the reasons pointed out by Wijffels and coworkers 2, 3 and Ratledge and Cohen 4, 5. A second option has been reviewed by Carlsson et al. 6 where the authors propose the use of biotechnology to tailor plants producing oils with distinct desired fatty acids and also to increase productivities.
A third alternative are microorganisms. Although there is a long history for the use of certain yeasts or fungi to produce triglycerides as the so-called single cell oils (SCO or microbial lipids), the strains studied only accumulate high amounts of lipids in the presence of large excess of carbon source and under nitrogen limitation; in addition, downstream processing is a further factor limiting industrial applications 5, 7. Modern metabolic engineering and synthetic biology tools now allow to create recombinant microorganisms overproducing virtually any desired compound as this has recently been demonstrated for an engineered Escherichia coli strain producing fatty acid alkyl esters, alkanes or wax esters 8 starting from simple carbon sources. Further examples for the microbial production of these compounds using engineered E. coli or Saccharomyces cerevisiae strains can be found in a recent review 9. These achievements also took advantage of the huge number of genome and protein sequences available in public databases (i.e., http://www.ncbi.nlm.nih.gov/RefSeq/). For instance, sequencing environmental samples from the Sargasso sea (1.2 million genes) 10 and the Global Ocean Survey project (6.1 million genes) 11, 12 almost doubled the number of protein sequences. This enabled the identification of novel enzymes with distinct function and selectivity required for tailoring fatty acid biosynthesis. Still, the manipulation of existing and the introduction of new pathways was not an easy task as it required to control the expression of individual enzymes, achieve desired fatty acid chain-length profiles by introducing plant derived enzymes, to eliminate side reactions, to deregulate fatty acid biosynthesis, to co-express a wax ester synthase and to form ethanol from pyruvate in E. coli. This might explain why the yields reported (e.g., 427 mg/L fatty acid alkyl ester) 8 are currently by at least one order of magnitude too low for commercial production of fatty acids and biofuels. However, further efforts, technology breakthroughs and sequence information will certainly enable the industrial use of metabolically engineered microorganisms for the production of fatty acids and related products in the next decade.
- 9Metabolic engineering of microbial pathways for advanced biofuels production. Curr. Opin. Biotechnol. 2011, 22, online. DOI: 10.1016/j.copbio.2011.04.024., , ,