HEMICELLULOSE HYDROLYSATE FROM AILANTHUS EXCELSA WOOD POTENTIALLY FERMENTABLE TO ETHANOL

Hemicellulose hydrolysate from acid-and alkali-impregnated wood chips of Ailanthus excelsa, a lignocellulosic substrate, was obtained using heating devices, namely, autoclave and microwave. Effects of various combinations of physical and chemical conditions on pretreatment was assessed based on release of hemicellulose hydrolysate from wood chips and yield of reducing sugars and ethanol from the hemicellulose hydrolysate. The various hydrolysis conditions tested were dilute acid- (0.7% sulphuric acid) or alkali- (3% sodium hydroxide) impregnated wood, two heating devices (autoclave and microwave), either singly or in combination, and single- or two-step hydrolysis process. Single-step acid hydrolysis applying microwave and autoclave as heating method gave almost similar results. The single-step autoclave-mediated dilute acid hydrolysis was chosen as optimal because it yielded the highest amount of pentoses (280 mg g⁻¹) and total sugars (285 mg g⁻¹). Hemicellulose hydrolysate after detoxification was found to be fermentable to ethanol (9.8-10.8 g L⁻¹) by pentose-fermenting yeast, Scheffersomyces stipitis. Ailanthus excelsa may therefore be a potent tree for bioethanol production.