INVESTIGADORES
ORDOÑEZ Maria victoria
congresos y reuniones científicas
Título:
OPTIMIZATION OF CULTURE CONDITIONS FOR THE DEVELOPMENT OF E. coli AND G. sulfurreducens SYNTROPHIC CO-CULTURES. ENHANCING BIO-ETHANOL PRODUCTION.
Autor/es:
GONZALEZ BLOTTA L.; FRITTAYON C.; SCHROTT, G.D.; ORDÓÑEZ, M.V.
Reunión:
Congreso; CONGRESO CONJUNTO SAIB-SAMIGE 2021; 2021
Institución organizadora:
Asociación Civil de Microbiología General (SAMIGE) - Sociedad Argentina de Bioquímica y Biología Molecular (SAIB)
Resumen:
World excess of glycerol, the main by-product of biodiesel industry, is causing traditional production and refinement industry of glycerol to shut down while novel applications for this, now abundant, carbon source are needed. The recent discovery, in 2006, that Escherichia coli is capable of fermenting glycerol with the subsequent production of several by-products, including ethanol, a source of clean fuels with proven less environmental impact than conventional fossil fuels, may offer a solution. During fermentation of glycerol, H2 is also produced and if not removed inhibits the fermentation process. Specifics pH, temperature and medium composition conditions have also been shown to be required. Our hypothesis is that growing E. coli together with Geobacter sulfurreducens will promote and improve the production of bio-ethanol since the latter is capable of using H2 generated by E. coli as an electron donor during its respiratory metabolism. In this work we evaluate a series of fundamental parameters for the development of co-cultures in order to optimize the syntrophic growth of these two bacteria. For this, G. sulfurreducens cultures were grown at different temperatures with acetate as carbon and electron source and Fe(III) citrate as final electron acceptor, in medium containing different concentrations of PO₄³⁻ and KCl, since these salts can inhibit glycerol fermentation in E. coli. Results show that G. sulfurreducens was capable of growing in all the conditions tested, including at 37ºC, the optimal temperature for fermentation in E. coli. In particular, a better growth was observed in mediums containing 0.18g/l of PO₄³⁻ while no significant difference was observed for different KCl concentrations. We also worked on the development of fermentation reactor systems for the fermentation of glycerol by E. coli. For this, external N2 gas bubbling, for removal of H2, and pH controllers, in order to maintain medium at optimal pH 6.3, were incorporated. Growth and glycerol consumption as well as ethanol production were evaluated during fermentative E. coli culture in modified MOPS medium with 10g/l glycerol. Our results for these systems show an exponential growth of E. coli with production of ethanol and the correlated consumption of glycerol. Growth was also significantly higher when compared to similar cultures grown in absence of external N2 bubbling and/or external pH control. Taken together these results are fundamental for our work in the the enhancement of fermentative efficiency in E. coli by means of the syntrophic growth with electro-active bacteria Geobacter, which may give place to novel biofuel production technology. Work supported by UNMdP, CONICET and ANPCyT.