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BACKGROUNDBermuda grass is an irrigated forage crop adapted to arid and subtropical zones. This grass can be effectively bioconverted into second-generation fuel ethanol. The aim was to optimize different acid hydrolyses conditions to maximize the release of C5 and C6 sugars from the forage with minimal production of microbial inhibitors.

RESULTSThe optimum conditions for H2SO4 were 12.5% solid to liquid, an acid concentration of 1.25%, and 75 min hydrolysis. The efficiencies after dilute acid and enzymatic treatments were 92.5, 73.5 and 89.9% for glucose, xylose and arabinose, respectively and the amounts of inhibitors were 8.2 kg m(-3) of acetic acid, 0.5 kg m(-3) of HMF, and 1.7 kg m(-3) furfural. For the HCl pretreatment, the optimum conditions were 12.5% solid to liquid fraction, 1.25% acid concentration and 37.5 min hydrolysis. These conditions released 56.2% glucose, 86.2% xylose and 48.3% of arabinose and generated 9 kg m(-3) of acetic acid, 0.5 kg m(-3) of HMF, and 2.6 kg m(-3) of furfural.

CONCLUSIONDual chemical and enzyme conversions are promising for production of second-generation ethanol from Bermuda grass. (c) 2013 Society of Chemical Industry