Production of n-butanol from concentrated sugar maple hemicellulosic hydrolysate by Clostridia acetobutylicum ATCC824

Abstract

Using fermentation to replace chemical processes in the production of acetone and butanol depends largely on the availability of inexpensive and abundant raw materials and efficient conversion of these materials to solvents. In this study solvent production of Clostridium acetobutylicum ATCC824 from nano-membrane concentrated hemicellulosic hydrolysate was investigated. Alkali pretreatment methods were applied to improve fermentability of nano-membrane concentrated hemicellulosic hydrolysate and solvent production by ATCC824. Results demonstrated that though nanofiltration could remove nearly all small molecular organic acids (acetic acid, formic acid), furfural and HMF, the resulting hydrolysate found to be still inhibiting solvent production of C. acetobutylicum. Solid particles separated from filtering hydrolysate were found not toxic to cells when xylose or glucose was used as carbon resource. Overliming treatment can significantly improve the ultimate butanol concentration to 7 g l−1 from 0.8 g l−1. Providing cells with more carbon source at the final stage of fermentation was found to have no impact on butanol production, but acetic acid and butyric acid production were found to increase significantly. The reasons leading to low solvent yield at later fermentation stages is not cell degeneration, but the toxicity of butanol and inhibitors remaining in the hydrolysate.