Desenvolvimento do processo de recuperação e purificação do xilitol produzido por rota biotecnológica utilizando o hidrolisado hemicelulósico do bagaço de caju como matéria-prima

Abstract

One type of industry that stands out in Brazil and especially in the State of Ceará is the cashew industry. Only in this state are produced about 30.9 thousand tons per year, and this production generates a large amount of residue, the cashew apple bagasse. This material is composed of cellulose, hemicellulose and lignin, and the molecules of polysaccharides can be broken, obtaining carbohydrates, mainly glucose and xylose, that can be used in different processes. Such sugars can be metabolized by microorganisms to synthesize products of commercial interest, such as xylitol. This carbohydrate has been used in several industrial sectors such as food, pharmaceutical, dental, among others. The medium cultivated for the production of xylitol by bioprocess using biomass hydrolyzates contains impurities, thus requiring separation and purification processes. In this context, the present dissertation aims to study the recovery and purification of the xylitol obtained by biotechnological production, using the yeast Kluyveromyces marxianus ATCC36907 and the hemicellulosic hydrolyzate of the cashew apple bagasse (CAB) as a culture medium, and its subsequent purification by the crystallization. The CAB was hydrolyzed by acid obtaining a hydrolyzate containing 15.66 g/L and 11.87 g/L of glucose and xylose, respectively, which was used to produce xylitol. After that, the study of the recovery and crystallization processes was started, evaluating the influence of different antisolvents (water, ethanol, isopropanol and protic ionic liquid 2-hydroxyethanolamine acetate – 2-HEAA), the percentage of antisolvent (10-90%) and the cooling rate (Vr, 0.25-0.50 °C/min), and the results were compared with commercial xylitol. In the experiments using xylitol PA a yield of 93% was obtained using 70% (v/v) ethanol as antisolvent and a linear cooling rate of 0.25 °C/min. The results using the proton ionic liquid 2-HEAA with xylitol PA showed an efficiency of 80% regardless of the cooling rate. The best conditions for the crystallization of the xylitol produced were using the 50% (v/v) isopropanol with a cooling rate of 0.5 °C/min, occurring a secondary nucleation, achieving a yield of 69.7% and purity of these crystals of 84.8, and in some cases, using ethanol with a linear cooling rate of 0.5 °C/min, 70% (v/v) isopropanol or protic ionic liquid 2-HEAA, did not occur at crystallization. By simple mass balance, using 1000 Kg of cashew apple bagasse, 7.86 g of xylitol was obtained in the best crystallization condition (50% isopropanol and Vr 0.5 °C/min) and this polyol presented characteristics similar to xylitol PA as, appearance and crystallinity. Then, it was concluded that xylitol can be obtained using hydrolyzate from cashew apple bagasse as the raw material and can be recovered by crystallization.