Modelagem e Simulação fenomenológica de biorreator para a produção de xilitol a partir de sisal (Agave sisalana) em meio com Candida guilliermondii

Abstract

Lignocellulosic residues submitted to biotechnological processes have aroused the interest of science due its economic viability, aiming to reduce the release of waste into the environment. This work consisted in the evaluation of kinetic parameters previously obtained and in the modeling of a perfectly agitated bioreactor on industrial scale, operating on a continuous basis. Initially, it was evaluated the use of data from two previous works carried out at the UFPB, which studied the biotechnological production of xylitol from the bagasse and fiber of sisal (Agave sisalana), both in inoculated medium with Candida guilliermondii. Preliminary analyzes showed that only one of the dissertations evaluated contained data that could be modeled. The variables manipulated in the simulation were initial substrate and cell concentration, residence time and feed flow. The simulations were performed at initial concentrations of substrate and cells, respectively, of 12.5 kg m-3 and 5 kg m-3, 37.5 kg m-3 and 10 kg m3, and 60.2 kg m-3 and 15 kg m-3, each of these initial concentrations evaluated at residence times of 1, 2 and 3 hours, and flow rate of 10, 5 and 3.33 m³ h-1. The kinetic parameters used were: Yx/s = 0.50, Yp/s = 0.34, max = 0.04 and Ks = 4, which were used to model the bioreactor, according to the Monod kinetics. The highest conversion (2.9164%) was observed when the initial xylose concentration was 12.5 kg m-³, and the initial cell concentration was 5 kg m-³, at the lowest feed rate (F = 3.33 m³ h-1) and the longest residence time (tr = 3h). The highest productivity (0.0134 kg m-³ h-1) was obtained with initial substrate of 60.2 kg m-³ and initial biomass of 15 kg m-³. The biotechnological process increased significantly when the same simulation was tested with the optimized kinetic parameters, with a conversion of 67.10%, productivity of 0.40 kg m-³ h-1 and consumption of xylose of 90, 01%. Thus, it can be inferred that the low results obtained in the present study are due to factors influencing the yeast metabolism: operational (pH, temperature and / or aeration); presence of inhibitors (lignin derivatives, acetic acid, HMF, furfural); adjustment of kinetic parameters from batch to continuous; production of ethanol