3 years ago

Electrochemically Driven Fermentation of Organic Substrates with Undefined Mixed Microbial Cultures

Electrochemically Driven Fermentation of Organic Substrates with Undefined Mixed Microbial Cultures
Mauro Majone, Alfredo Miccheli, Marianna Villano, Enza Palma, Paola Paiano
Growing scientific interest in mixed microbial culture-based anaerobic biotechnologies for the production of value-added chemicals and fuels from organic waste residues requires a parallel focus on the development and implementation of strategies to control the distribution of products. This study examined the feasibility of an electrofermentation approach, based on the introduction of a polarized (−700 mV vs. the standard hydrogen electrode) graphite electrode in the fermentation medium, to steer the product distribution during the conversion of organic substrates (glucose, ethanol, and acetate supplied as single compounds or in mixtures) by undefined mixed microbial cultures. In batch experiments, the polarized electrode triggered a nearly 20-fold increase (relative to open circuit controls) in the yield of isobutyrate production (0.43±0.01 vs. 0.02±0.02 mol mol−1 glucose) during the anaerobic fermentation of the ternary mixture of substrates, without adversely affecting the rate of substrate bioconversion. The observed change in the fermentative metabolism was most likely triggered by the (potentiostatic) regulation of the oxidation–reduction potential of the reaction medium rather than by the electrode serving as an electron donor. Multicultural magic: Electrofermentation provides new opportunities to control mixed microbial culture bioprocesses. The presence of a polarized graphite electrode was found to affect the fermentation of glucose when supplied with acetate and ethanol as co-substrates, boosting the production of isobutyric acid. Regulation of the external redox potential was the main trigger of the electrofermentation process.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/cssc.201700360

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