Butanol production by fermentation of fruit residues

The feedstock of the Acetone-Butanol-Ethanol (ABE) fermentation is a key issue for the economic success of the biotechnological route to produce biobutanol. Residues from agro-alimentary industries are particularly interesting as renewable substrates for the ABE fermentation because they are abundant and un-competitive with food sources. The residues are also a pressing issue for industries because more than 50% of the processed feedstocks are discharged and their disposal is particularly expensive. However, the high fraction of sugars of the residues makes them a promising interesting feedstock for the production of butanol. This contribution is about the characterization of the ABE fermentation by Clostridium acetobutylicum DSM 792 using sugars from fruit peels. Apple and pear peel extracts were tested as substrate for the fermentation. Batch tests were carried out under a wide interval of peels to water mass ratio. The conversion process was characterized in terms of metabolites and cell production, sugars conversion, specific rate of butanol production and of sugar consumption, butanol and cell yields. The fermentation tests with feedstock peels to water mass ratios lower than 1/6 were characterized by total sugar conversion and low butanol concentration (<8.5 g/L). Tests with feedstock peels to water ratios higher than 1/8 were characterized by high butanol production (about 14 g/L) and incomplete sugar conversion.