By pyrolyzing biomass such as cornstalks and sawdust and feeding the oil product to the microbes, a new generation of biofuels is being produced. However, the microbes are facing some difficulties which the researchers from Iowa State University are trying to solve by allowing the microbes to adapt to the oil feed via genetic mutation.
“The goal is to produce bio-renewable fuels and chemicals in a manner that’s economically competitive with petroleum-based processes,” said Laura Jarboe, the leader of the research team and professor in biochemical engineering. Thus, the group came up with a hybrid approach by incorporating biochemical conversion into thermochemical conversion, to efficiently produce biofuels and biochemical simultaneously.
The Iowa researchers first rapidly heated or burned biomass, also called pyrolysis sugars, without oxygen, but with a catalyst. The resulting product is brown oil that has molasses-like smell. This bio-oil is then fed to two types of microbes for conversion to biofuel. The E.coli bacteria acts on the bio-oil’s sugar-rich fraction by converting levoglucosan to ethanol and lactic acid. In the meantime C. reinhardtii microalgae convert the bio-oil’s acetate-rich portion to lipids for biodiesel.
Unfortunately, there are contaminants in the bio-oil that the microbes dislike. The researchers are hoping that by using a directed evolution technique, which subjects the microbes to increasing concentrations of bio-oil, the microbes will evolve such that they will be more tolerant of the toxins.
“It could be a mistake that’s immediately lethal or it could be a mistake that helps the microbe tolerate the problematic compounds and it grows faster,” said Jarboe.