Xylitol bioproduction from wheat straw: hemicellulose hydrolysis and hydrolyzate fermentation

A 2 2 central composite design with five center points was performed to estimate the effects of temperature (120, 130 and 140 °C) and acid loading (100, 150 and 200 mg g −1 ) on the yield of monomeric xylose recovery from wheat straw hemicellulose ( Y S/RM ). Under the best hydrolysis condition (140 °C and 200 mg g −1 ), a Y S/RM of 0.26 g g −1 was achieved. After vacuum concentration and detoxification by pH alteration and active charcoal adsorption, the hydrolyzate was used as source of xylose for xylitol bioproduction in a stirred tank reactor. A xylitol production of 30.8 g L −1 was achieved after 54 h −1 of fermentation, resulting in a productivity ( Q P ) of 0.57 g L −1 h −1 and bioconversion yield ( Y P/S ) of 0.88 g g −1 . The maximum specific rates of xylose consumption and xylitol production were 0.19 and 0.15 g g −1 h −1 , respectively. Copyright © 2006 Society of Chemical Industry