Corn stover conversion into bioethanol and xylitol through an integral bioprocess: Kinetic study and modelling

Abstract

BackgroundCorn stover residue is an important lignocellulosic material with a biochemical composition that arouses an interest in transforming into bioethanol and high added value product, such as e.g., xylitol. MethodsHydrolysis experiments were carried out in a semi-pilot reactor of 12 L capacity. Fermentation experiments were conducted in a 1 L batch bioreactor capacity. Detailed kinetic study of the Candida guilliermondii NRC 5578 growth was carried out. Fermentation and the xylitol production process were modelled. Significant FindingsThe used crude corn stover residue was composed of 11.1 % of lignin, 27.1 % of hemicellulose, 32.6 % cellulose, 24.5 % pentosanes, and 33.0 % of α-cellulose. Reconditioning liquid fractions of prehydrolysate and hydrolysate at 1.4 % (w/v) of H2SO4 were determined for the prehydrolysate 5.31 g/L, 9.07 g/L, 3.07 g/L, 11.2 g/L, 3.24 g/L, 3.89 and 2.56 g/L for pentoses, hexoses, arabinose, xylose, mannose, glucose, and fructose, respectively, and for hydrolysate 15.2 g/L of glucose. The higher values of maximum specific growth rate were registered for control experiments and compared to prehydrolysated and hydrolysated cultures. The highest ethanol formation rates of 2.29 g/(g L) and 0.117 g/(g L) in synthetic and hydrolysated cultures, respectively, were registered when 7 g/L glucose was used as carbon source.