Dilute-acid hydrolysis for optimization of xylose recovery from rice straw in a semi-pilot reactor

Rice straw is composed of pentose that can be used as a raw material for the production of many types of useful compounds. One of these is xylitol, with a potential application in the food and medical areas. The increasing interest in biotechnological processes employing lignocellulosic residues is justifiable because these materials are cheap, renewable and widespread sugar sources. The objective of the study was to determine the effects of H2SO4 concentration and reaction time on the production of sugars (xylose, glucose and arabinose) and on the reaction byproducts (furfural, hydroxymethylfurfural (HMF) and acetic acid). Dilute sulfuric acid was used as a catalyst for the hydrolysis of rice straw at 121°C in a 350-l batch hydrolysis reactor. Rationale for conducting this study was determined based on a central composite statistical design. Response surface methodology (RSM) was adopted to optimize the hydrolysis conditions aiming to attain high xylose selectivity. The optimum H2SO4 concentration of 1% and reaction time of 27 min was found. Under these conditions, 77% of xylose yield and 5.0 g g−1 of selectivity were attained.