Optimization of activated charcoal detoxification and concentration of chestnut shell hydrolysate for xylitol production

Objectives To increase xylose concentration of the chestnut shell hemicellulosic hydrolysate with an acceptable phenolic compound level in order to enhance xylitol production by Candida tropicalis M43. Results The xylose concentration and total phenolic compound concentration of the hydrolysate were obtained as 33.68 g/L and 77.38 mg gallic acid equivalent/L, respectively by optimization of detoxification parameters and concentration level (60 degrees C, 115 min contact time, 5.942% (w/v) dosage of activated charcoal, 120 strokes/min shaking rate and 0.2 volume ratio). Xylitol production was achieved in the hydrolysate by using Candida tropicalis M43. The maximum xylitol concentration was 6.30 g/L and productivity, yield and percentage of substrate conversion were calculated as 0.11 g/L h, 19.13% and 97.79%, respectively. In addition, the chestnut shell hydrolysate fortified with xylose and the maximum xylitol concentration increased to 18.08 g/L in the hydrolysate-based medium containing 80 g/L xylose. Conclusions Optimizing detoxification conditions with concentration level was found to be useful for enhancing xylitol production. In addition, fortification of the hydrolysate caused a three fold increase in maximum xylitol concentration.