Researchers make hydrogen as cellulosic ethanol coproduct

Ethanol Producer Magazine

By Susanne Retka Schill
July 16, 2012

Rather than focusing on a single microbe capable of converting cellulose to ethanol in a fermenter, researchers at Michigan State University are mimicking nature, culturing two bacteria that grow synergistically. The process creates two fuels, ethanol and hydrogen, the latter being produced from electricity generated by one of the bacteria.

Microbiologist Gemma Reguera explained her team of microbiologists at MSU are known for their work with the bacterium, Geobacter sulfurreducens, used for developing bioeletrochemical systems known as microbial electrolysis cells. The work done by MSU chemical engineer Bruce Dale treating corn stover and other waste biomass with the ammonia fiber expansion (AFEX) process was intriguing to them because it mimics what fungi do in in nature to remove lignin and facilitate the hydrolysis of cellulose for symbiotic microorganisms. They then looked for natural organisms that would degrade AFEX pretreated cellulose into ethanol. “They always produce ethanol and something else,” she explained, “and that something is usually acids that bring the pH in the fermentation broth down and back-inhibit the bacterial activity. This really slows growth or kills the fermentation organism.” Mimicking nature again, they looked for a bacterium that would produce ethanol and compounds that would support the electron-producing Geobacter, thus removing ethanol-production inhibitors from the fermentation broth.

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