(675b) Hybrid Thermochemical Processing: Fermentation of Pyrolytic Substrates

As a temporary storage unit of sunlight-derived energy and atmospheric carbon, biomass is an excellent source of carbon and energy for the production of biorenewable fuels and chemicals. However, the cost- and energy-efficient release of fermentable sugars from this biomass is challenging, largely due to the complex structure of lignocellulose. Thermochemical processing of biomass by fast pyrolysis provides a non-enzymatic route for depolymerization of biomass into fermentable substrates that can be used for the biological production of fuels and chemicals. Fermentative utilization of these pyrolytic substrates faces two formidable challenges. First is the fact that most bio-oil-associated sugars are present in the anhydrous form. Metabolic engineering has enabled utilization of the main anhydrosugar, levoglucosan, in workhorse biocatalysts. The second challenge is the fact that bio-oil is rich in microbial inhibitors. Biomass processing, collection of the pyrolytic substrates, detoxification of the substrates prior to fermentation and increased robustness of the biocatalyst are effective methods for addressing this inhibition. Here we describe metabolic engineering efforts to enable utilization of these pyrolytic substrates.