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

Abstract

Background: Corn 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. Methods: Hydrolysis 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 Findings: The 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 a-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