Production of butanol (a biofuel) from agricultural residues: Part I – Use of barley straw hydrolysate

Fermentation of dilute sulfuric acid barley straw hydrolysate (BSH; undiluted/untreated) by Clostridium beijerinckii P260 resulted in the production of 7.09 gL−1 ABE (acetone butanol ethanol), an ABE yield of 0.33, and productivity of 0.10 gL−1 h−1. This level of ABE is much less than that observed in a control experiment (21.06 gL−1) where glucose (initial concentration 60 gL−1) was used as a substrate. In the control experiment, an ABE yield of 0.41 and productivity of 0.31 gL−1 h−1 were observed. This comparison suggested that BSH is toxic to the culture. To reduce this potential toxicity effect, BSH was treated with lime [Ca(OH)2] followed by fermentation. The treated BSH resulted in a successful fermentation and ABE concentration of 26.64 gL−1 was achieved. This was superior to both glucose and untreated BSH (initial sugar 60 gL−1) fermentations. In this fermentation, an ABE yield of 0.43 and productivity of 0.39 gL−1 h−1 (390% of untreated/undiluted BSH) was obtained. It should be noted that using lime treated BSH, a specific productivity of 0.55 h−1 was obtained as compared to 0.12 h−1 in the control fermentation suggesting that more carbon was directed to product formation.