Integrated ABE fermentation-adsorption process for enhanced butanol production by Clostridium acetobutylicum

The biotechnological route to produce butanol via Acetone-Butanol-Ethanol fermentation still suffers of several disadvantages. On one hand, the low maximum butanol concentration due to the butanol toxicity to microorganisms and the low specific butanol productivity severely limit the industrial development of the butanol production. On the other hand, a low-costandenergyconsumingtechnologytorecoverthebutanol from the low-concentration broth is still a target of the research. Therecoveryandconcentrationofbutanolbymeansofadsorption technique has several advantages in terms of biocompatibility and stability, as well as of the process economy. Therefore, the butanol recovery by adsorption has high potentiality for industrial application. Theaimofthiscontributionistoreportrecentresultsofastudy carriedoutinNapoliaspartoftheHORIZON2020project"Sustainable production of next generation biofuels from waste streams - Waste2Fuels" (GA - 654623). Clostridiumacetobutylicumwasusedforthecontinuousfermentation process. The conversion was carried out in 4 packed bed biofilm reactors (PBBRs) connected in series: the first reactor of the series was kept under acidogenesis, the successive reactors were kept under solventogenesis. A glucose bearing solution was continuously fed to the reactors. Theadsorption/desorptionprocesswascarriedoutinfixed-bed column for butanol-water and for synthetic fermentation broth modelsolutions.AmberliteXAD-7wasusedasadsorbentmaterial. The integration of the PBBRs with an adsorption recovery unit was successfully developed and operated. Thebutanolproductivityandthefinalconcentrationofbutanol were very competitive.