The threat of unsteady crude oil supply and the negative impact of fossil fuels on the environment have put great pressure on the society to seek renewable fuel alternatives, which initiated a renewed interest in the production of fuels and chemicals via fermentation processes.  Here we report a unique Clostridium species, which has both cellulolytic and solventogenic properties in generating energy-rich compounds from renewable feedstock under mesophilic conditions.  End product inhibition in acetone-butanol-ethanol (ABE) fermentation process can be reduced by enzymatic conversion of lipophilic solvent butanol to non-toxic and more economically valuable products, such as butyl-butyrate.  In this study, we aimed at setting up an integration of ABE fermentation process and lipase-catalyzed esterification to achieve:  i) co-production of butanol and butyl-butyrate; ii) high amount of butyl-butyrate in the fermentation broth.  In the fermentation medium, addition of lipase at 48 h could only produce 0.48 g/L butyl-butyrate and 13.67 g/L butanol by Clostridium sp. BOH3 from 60 g/L xylose.  By simultaneous in situ extraction using the model extractant, such as hexadecane, and fed with butyric acid, the batch fermentation process produced 4.10 g/L butyl-butyrate and 17.33 g/L butanol from 60 g/L xylose.  Furthermore, when different fuels were used as extracant, such as biodiesel, paraffin oil and- kerosene, kerosene could more efficiently drive the enzymatic reaction towards the synthetic side (16.68 g/L butyl-butyrate in the solvent phase).  This integration process will not only improve butanol production and enrich the jet fuel (e.g., kerosene), but also reduce the cost of product recovery.

Integration of acetone-butanol-ethanol (ABE) fermentation process and enzyme catalyzed butyl-butyrate production

247th National Meeting (2014)

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