Chemical Engineering Seminar- The emerging importance of microbial consortia in the biotechnology for sustainability

In microbial fermentations to produce metabolites, at least 33% of the sugar-substrate carbon is lost as CO2 during pyruvate decarboxylation to acetyl-CoA, which is typically the starting point for metabolite biosynthesis. Previous attempts to reduce this carbon loss focused on engineering a single organism aiming to achieve that goal. In nature, most microorganisms live in complex communities where syntrophic interactions result in superior resource utilization. Here we show that a synthetic Clostridium syntrophy consisting of a solventogen C. acetobutylicum, which converts carbohydrates into a variety of chemicals, and an acetogen C. ljungdahlii which fixes CO2. This syntrophic system performed robustly to achieve better efficiencies than either organism alone by improving the carbon recovery into metabolites by 20%, thus achieving theoretical yields as defined by electron availability. Our data shows that in this syntrophic co-culture, the two organisms exchange metabolites directly, frequently leading to interspecies cell-wall/membrane fusion events, which we probed using advanced electron microscopy tools including correlative fluorescence/TEM/SEM microscopy and electron tomography. Such fusion events have not been previously reported and may be more frequent than is currently appreciated in natural consortia. In addition, this syntrophy results in novel biosynthetic pathways/ capabilities that neither of the two organisms alone possesses. This and other syntrophies expand the metabolite space by generating metabolites that neither organism can produce alone. Syntrophic cultures offer a flexible platform for metabolite production with superior carbon recovery that can also be applied to electron-enhanced fermentations enabling even higher carbon recovery.

Remote attendance possible at: https://epfl.zoom.us/j/164678393