Metabolic Engineering of Cyanobacteria for Direct Conversion of CO2 to Hydrocarbon Biofuels
Cyanobacteria are oxygenic photosynthesizers like plant and algae and hence can capture CO2 via the Calvin cycle and convert it to a suite of organic compounds. They are Gram-negative bacteria and are well suited for synthetic biology and metabolic engineering approaches for the phototrophic production of various desirable biomolecules, including ethanol, butanol, biodiesel, and hydrocarbon biofuels. Phototrophic biosynthesis of high-density liquid biofuels in cyanobacteria would serve as a good complement to the microbial production of biodiesel and hydrocarbons in heterotrophic bacteria such as Escherichia coli. Two groups of hydrocarbon biofuels that are being considered in microbial production systems are alkanes and isoprenoids. Alkanes of defined chain lengths can be used as drop-in fuel similar to gasoline and jet fuel. Many cyanobacteria synthesize alkanes, albeit in minute quantities. Optimizing the expression of the alkane biosynthesis genes and enhancing the carbon flux through the fatty acid and alkane biosynthesis pathways should lead to the accumulation and/or secretion of notable amounts of alkanes. It also becomes important to understand how to control the chain lengths of the produced alkane molecules. Isoprenoids, e.g., the monoterpene pinene and the sesquiterpene farnesene, are considered precursors for future biodiesel or next-generation jet fuel. Cyanobacteria produce carotenoids and extending the carotenoid biosynthetic pathways by the introduction of constructs for appropriate terpene synthases should allow the biosynthesis of selected mono- and sesquiterpenes.
KeywordsFatty Acid Synthesis Algal Biofuel Raceway Pond Synechococcus Elongatus Geranyl Pyrophosphate
This work was supported in part by U. S. Department of Energy Contract DE-AC02-05CH11231 with Lawrence Berkeley National Laboratory. Funding from the DOE-LDRD grant CyanoAlkanes is acknowledged.
- Deng MD, Coleman JR (1999) Ethanol synthesis by genetic engineering in cyanobacteria. Appl Environ Microb 65:523–528Google Scholar
- Khosla C (2008) Microbial synthesis of biodiesel Book Microbial synthesis of biodiesel. Stanford University, StanfordGoogle Scholar
- Li W, Liu XX, Wang W, Sun H, Hu YM, Lei H, Liu GH, Gao YY (2008) Effects of antisense RNA targeting of ODC and AdoMetDC on the synthesis of polyamine synthesis and cell growth in prostate cancer cells using a prostatic androgen-dependent promoter in adenovirus. Prostate 68:1354–1361PubMedCrossRefGoogle Scholar