LS9 Transplants Bacterial Genes to Produce Diesel from Sugars
The LS9 researchers discovered the genes involved by comparing the genomes of 10 strains of cyanobacteria (also called blue-green algae) that naturally produce alkanes with a very similar strain that produces no alkanes. They identified 20 genes that the alkane-producing strains had but that the non-alkane-producing strain lacked. From there, the researchers narrowed down the possibilities until they identified the genes and enzymes necessary for alkane production. They confirmed their discovery by incorporating the genes into E. coli and measuring the alkanes that the bacteria subsequently made. The bacteria secrete the alkanes, which can then by easily collected and used as a fuel.Such artificially programmed bacteria (and algae) will provide the most efficient means of converting CO2 directly to hydrocarbons. Humans will find it difficult to create economical processes to make long chain alkanes from CO2, using the low levels of CO2 found in the atmosphere (0.04%).
Organisms make alkanes via a complex process that produces fatty acids from carbon dioxide or sugars. The fatty acids are then converted by the organisms to an aldehyde that includes a carbon atom bonded to an oxygen atom (together they create what's called a carbonyl group). The enzyme aldehyde decarbonylase helps remove this group to form a chain of hydrogen and carbon atoms--the hydrocarbon. The natural process produces a collection of hydrocarbons of various lengths that are comparable to the hydrocarbon molecules in diesel. _TechnologyReview
More on LS9 from GCC:
Researchers at LS9 have discovered an alkane biosynthesis pathway in cyanobacteria; i.e., a metabolic pathway that produces alkanes—the major hydrocarbon constituents of gasoline, diesel and jet fuel—in a direct, simple conversion from sugar.By taking the genes from one species of bacteria and transplanting them into E. Coli, the scientists are making use of a bacterial production platform (E. Coli) which is quite familiar to biotechnologists, pharmacologists, and industrial microbiologists. Expect much more of this genetic "mixing and matching" to create optimal microbial production platforms.
When the newly identified alkane operon is expressed in E.coli, the bacteria produce and secrete C13 to C17 mixtures of alkanes and alkenes. This discovery is the first description of the genes responsible for alkane biosynthesis and the first example of a single step conversion of sugar to fuel-grade alkanes by an engineered microorganism. A paper on the work was published in the 30 July issue of the journal Science.
Alkanes are naturally produced by diverse species, but the genetics and biochemistry behind this biology have not been well generally well understood. The LS9 team looked into the genomes of cyanobacteria that produce alkanes in nature, evaluating many and identifying one that was not capable of producing alkanes, said Andreas Schirmer, Associate Director of Metabolic Engineering at LS9, and lead author on the paper. By comparing the genome sequences of the alkane producing and non-producing organisms, LS9 was able to identify the responsible genes. _GCC
Labels: microbial energy