A research team led by Laura Jarboe, an Iowa State University (ISU) assistant professor of chemical and biological engineering, is feeding pyrolysis made pyrolytic sugars of bio-oil to microbes for fermentation.
A fast heating pyrolysis rapidly heats such biomass such as corn stalks and sawdust that’s fed to the microbes E. coli and C. reinhardtii. The microbes are understandably less than thrilled. The result of the pyrolytic thermochemical process is thick, brown oil that smells like molasses.
The E. coli are supposed to turn the levoglucosan in the sugar-rich fraction of bio-oil into ethanol and lactic acid; the C. reinhardtii are supposed to turn acetate-rich fractions into lipids for biodiesel.
This is part of the hybrid approach ISU researchers are using to produce the next generation of biofuels. They’re combining two conversion paths – thermochemical and biochemical – to find efficient ways to produce renewable fuels and chemicals.
Jarboe explains the motive with, “The goal is to produce biorenewable fuels and chemicals in a manner that’s economically competitive with petroleum-based processes.”
The microbes’ disappointment comes from contaminants and toxins in the bio-oil that are getting in the way of the fuel production. Jarboe and the research team are experimenting with pre-treatments of the bio-oil that could reduce the toxicity. And they’re working to develop microbes that can tolerate the contaminants.
This is the leading bleeding cutting edge of the newest idea. The team is intellectually rich including Robert C. Brown, the Iowa Farm Bureau Director of Iowa State’s Bioeconomy Institute, an Anson Marston Distinguished Professor in Engineering and the Gary and Donna Hoover Chair in Mechanical Engineering; Zhiyou Wen, an associate professor of food science and human nutrition; Zhanyou Chi, a post-doctoral research associate for Iowa State’s Center for Sustainable Environmental Technologies; Tao Jin, a doctoral student in chemical and biological engineering; and Yi Liang, a doctoral student in food science and human nutrition.
The project has some finance legs with support from a three-year, $300,000 grant from the National Science Foundation and a three-year, $315,020 grant from the Iowa Energy Center.
The prospects are pretty hopeful. The researchers are using a technique called directed evolution to produce microbes that are more tolerant of the contaminants in bio-oil. The microbes are grown with higher and higher concentrations of bio-oil and as they divide, they replicate their DNA. Sometimes there are replication mistakes that lead to useful mutations.
Jarboe explains in simple terms, “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. At the end of the process, we want to say, ‘Hey, I’ve got a great bug.’”
Every day researchers check the experiments for signs of progress. So far, Jarboe said the evolving bacteria and microalgae have been able to tolerate slightly higher concentrations of bio-oil.
When mutations eventually produce a better breed of microbe, the researchers will analyze genomic data to learn and understand the important mutations. That will allow researchers to duplicate the microbes for better biofuel production.
Jarboe said development of those hungry, robust microbes could lead to important advancements in biofuel production: a hybrid process that’s biorenewable, fast, cheap and doesn’t depend on food crops as a source of biomass.
The task is to find a solution for the mixture of carbon monoxide and hydrogen that’s produced by the partial combustion of biomass in a gasifier. The fermentation process slows when researchers dissolve the gas into a liquid that can be used by microorganisms to produce biofuels. They’re looking for bioreactor technologies that boost the mass transfer of the synthesis gas without adding energy costs.
The folks at ISU have been at this a while. Brown keeps a small vial of brown, sweet-smelling liquid produced by the fast pyrolysis on his office table. We had a look at the pyrolysis process for sugar rich and acetate-rich fractions over a year ago.
The hybrid idea is driven by economics. Brown said almost a year and a half ago, “Biological processes occur well below the boiling point of water, while thermal processes are usually performed hundreds of degrees higher, which makes it hard to imagine how these processes can be combined.”
Combining the two processes offers major advantages. High temperature pyrolysis breaks down biomass to substrates that can be fermented to desirable products. Fermentation makes fuel and chemical precursors at low cost and with useful waste materials. Used together perhaps a far larger biomass base could be part of the fuel cycle.
The team is at the very leading edge of research and has a good grip on getting further along. The idea and the progress are well worth keeping an eye on.