Dilute acid hemicellulose hydrolysates from corn cobs for xylitol production by yeast

Dilute acid hemicellulose hydrolysate, comprised mainly of xylose, was obtained from ground corn cobs after dilute hydrochloric acid (2%, wt) hydrolysis at 100°C for 2 h. Similar acid hydrolysate was also obtained after the corn cobs were treated with 10% ammonium hydroxide at 26°C for 24 h. Neutralized hydrolysates containing ca. 130 g/l xylose were used as the substrate for xylitol production by a xylitol-producing yeast, Candida sp. 11-2. Ammonia-treated hydrolysate was a better substrate for xylitol production. Xylose was consumed within 36 h with a specific xylitol productivity of 1.94 g/l•h and a xylitol weight yield of 0.57 g/g xylose utilized. In contrast, neutralized hemicellulose hydrolysate obtained without prior ammonia treatment required anion exchange resin treatment to be fermented by yeasts. The specific productivity and weight yield of xylitol from anion exchange resin-treated hydrolysate were comparable to that from an ammonia-treated sample.