Sugarcane bagasse hydrolysis with phosphoric and sulfuric acids and hydrolysate detoxification for xylitol production

The effectiveness of phosphoric acid to release xylose from sugar-cane bagasse hemicellulose was assessed through a 23 full factorial design. The maximum xylose concentration in the hydrolysate (17.1 g dm(-3)) was attained when the bagasse was treated at 160degreesC for 60 min, using 70 mg of phosphoric acid per gram of dry-bagasse. Hydrolysis carried out with sulfuric acid, under optimum conditions previously determined, provided a hydrolysate with a similar xylose concentration (17.2g dm(-3)). After vacuum concentration, these hydrolysates were detoxified and used for xylitol production with the yeast Candida guilliermondii. Two different detoxification strategies, which consisted of adjusting the pH of the hydrolysates to 5.5 with either calcium oxide or ammonium hydroxide, both followed by active charcoal adsorption, were tested. The best xylitol productions (18.1 and 19.2 g dm(-3)) were observed when calcium oxide was used to adjust the pH of both the phosphoric and the sulfuric acid hydrolysates, respectively. (C) 2004 Society of Chemical Industry.