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 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. Published by Elsevier Ltd.