(563a) Investigation of Unique Interspecies Interactions in a Synthetic and Syntrophic Clostridium Co-Culture

Kamil Charubin^1,2, and E. Terry Papoutsakis^1,2,3

¹ Department of Chemical and Biomolecular Engineering, University of Delaware, Newark DE.

² Delaware Biotechnology Institute, Newark DE.

³ Department of Biological Sciences, University of Delaware, Newark DE.

In microbial fermentations at least 33% of the sugar substrate is lost as CO₂ waste during the pyruvate decarboxylation, with the corresponding loss of electrons in the form of H₂. To improve fermentation efficiencies we designed a synthetic and syntrophic co-culture of Clostridium acetobutylicum, which is capable of converting a variety of sugars into solvents, and C. ljungdahlii, an acetogen capable of fixing CO₂ in the presence of H₂. The co-culture was found to reach higher carbon recoveries and produce non-native products i.e. isopropanol and 2,3-butanediol. The physical contact between both strains was found to be crucial in maintaining the unique co-culture phenotype. The interspecies interaction led to a metabolite exchange, which allowed for the generation of non-native products, and a differential gene expression of the key enzymes in the co-culture. To investigate the interspecies interaction between C. acetobutylicum and C. ljungdahlii more closely we first engineered a fluorescent C. acetobutylicum strain that does not require O₂ for fluorophore activation. In combination with fluorescent dyes, correlative confocal and electron microscopy was used to study the timeframe and the extent of interactions between both strains in the co-culture.

SUPPORTED by the National Science Foundation through the NSF grant (Award No. CBET-1511660) and the IGERT fellowship (Award No. 1144726), and the Army Research Office (Award No. W911NF-17-1-0343).