Simulação do processo de separação do xilitol proveniente da rota biotecnológica de fermentação da xilose utilizando os softwares livres COCO e Scilab

Abstract

Within a context of a growing global market of low-calorie products, it is possible to highlight the production of sweeteners – products whose sweetening capacity is similar to sucrose – among which is xylitol, a sugar metabolized independently of insulin action – which makes it tolerable by diabetics – found naturally in fruits, vegetables, yeasts, lichens and algae. Due to the economic unfeasibility of the polyol’s conventional methods of obtaining – solid-liquid extraction and catalytic reduction of xylose – many studies have been set up to formulate alternative means to produce it. Considered very promising, the biotechnological production consists of xylan fermentation, obtained from the acid or enzymatic hydrolysis of lignocellulosic materials rich in xylan, such as hemicellulosic hydrolysate of sugarcane bagasse, by capable microorganisms and consequent release of xylitol, as well as other metabolites in fermentation broth. Obtaining the product of interest gets related to its separation from the broth that, due to its complexity, presents a high cost in relation to the rest of the process, which motivates, therefore, the study of several techniques that enable it. Some examples discussed in the literature are: use of zeolites, resins, crystallization, activated carbon adsorption, liquid-liquid extraction, precipitation and membrane application. Therefore, the present study aimed the simulation, using the free softwares COCO and Scilab, of the fermentative step and the synthesis of the separation process that offers possible means to obtain xylitol produced in a microbiological environment, as well as the analysis of the behavior of the system and the properties of the substances involved in the simulation environment. For this, an integration module was used between the two softwares that enabled the resolution of the system of ordinary differential equations that describes the kinetic model of xylitol production by xylose fermentation by Candida tropicalis. From the result obtained for the system in the Scilab routine, using the properties of the feed stream defined in the COCO environment, the production of xylitol, which was 1260.37 kg.h-1, as well as the secondary metabolites, ethanol e glycerol, 237.14 kg.h-1 and 284.56 kg.h-1, respectively, that compose the flow to be purified in the subsequent steps, could be estimated. The proposed separation process consisted of liquid-liquid extraction using ethyl acetate as solvent and presented a reasonable behavior in terms of xylitol recovery, with loss of less than 1%, as reported by similar researches. Subsequently, unitary operations were used for solvent recovery as well as for the concentration of xylitol stream, resulting in a current with 73% w/w xylitol, which is equivalent to 0.18 kg per kg of feed xylose, and would in practice make it possible to crystallize and obtain the product of interest with a high degree of purity.