Research Article
Branco R. F, Santos J. C an
Abstract
Xylitol production by fermentation process is widely studied. However, few works describes the enzymatic production of this polyalcohol. This works aims to determine a model that could explain the xylitol enzymatic production as a function of major variables in this process. For this purpose we applied an adequate statistical analysis and response surface methodology (RSM). Initially, variables were selected using a 25-1 fractioned factorial design. Xylose and NADPH concentrations were chosen for the optimization experiments. In order to use the RSM, experiments according to a 22 factorial design with star points and triplicate in the center were carried out. The statistical analysis resulted in a quadratic model which could explain 98.6 % of the volumetric productivity in xylitol in function of xylose and NADPH concentrations. Using predicted experimental conditions of 7.0, 25ºC, 1.2 mM NADPH, 0.34 M xylose, glucose 0.2 U mg-1 xylose reductase and 0.2 U mg-1 glucose dehydrogenase, this solid model was possible to achieve in batch reaction a xylitol volumetric productivity of 1.58 ± 0.05 g L-1 h-1 with stoichiometric xylose/xylitol conversion efficiency. These values are considered higher and significant in comparing with the traditional fermentation processes. Our results contribute for development of a novel and promising alternative process for xylitol production.