Modeling of the xylitol production from sugarcane bagasse by immobilized cells

BACKGROUND Xylitol is a polyalcohol widely used in the pharmaceutical, medicine and food industry because of its anti-cariogenic properties and low caloric value, with a sweetness equal to sucrose. Xylitol can be produced chemically or through a biotechnological route, though the last alternative still does not reach the yields to satisfy the industrial needs. The biotechnological route is an important alternative for the valorization of agroindustrial waste rich in hemicellulosic sugars, such as cane sugar bagasse, rice straw, banana peel, among others. To reduce the experimental costs, mathematical modeling is useful for determining the fermentation operation conditions and to improve the overall process. RESULTS A dynamic mathematical model for the description of xylitol production from sugarcane bagasse by Candida guilliermondii cells entrapped was developed. For the description of the microbial growth rate, free and immobilized microorganisms situations were considered in the kinetic model, including mass transfer effects. Experimental data reported in the literature were used to validate the proposed model. Additionally, a parametric estimation by the Levenberg-Marquardt method and a parametric sensitivity analysis was also performed. CONCLUSION The best experimental fit was obtained when the effects of inhibition by substrates are included in the kinetic model reaching a global determination index R-2 > 0.95. Furthermore, this proposed model allowed us to evaluate the restraints that are generated due to the internal and external mass transfer processes of the immobilized medium. The parametric sensitivity analysis demonstrated the optimal operation conditions where the xylitol production can be favored. (c) 2020 Society of Chemical Industry