Produção, caracterização reológica e coloidal de goma xantana biossintetizada a partir de resíduo de cervejarias artesanais e uso como sistema de liberação controlada de sulfadiazina de sódio

Abstract

Beer production has increased exponentially in the last 20 years, resulting in the annual generation of millions of tons of waste, such as malt bagasse. Currently, this residue is destined in almost its entirety, for the elaboration of animal feed. However, due to its chemical composition being rich in sources of fiber, carbohydrates and proteins, malt bagasse may have the potential to be used for other purposes with greater added value. In this theme, the use of malt bagasse from breweries for the production of biopolymers, such as xanthan gum (XG), would avoid environmental problems and represent a productive and economic alternative for the country, in addition to generating jobs. Xanthan gum is an extracellular polysaccharide with a cellulose-based main chain and trisaccharide side branches containing glucuronic acid and pyruvic acid that give it an anionic character. Obtained by the fermentation of carbon sources and the action of the bacterium Xanthomonas campestris, they are considered safe and approved for use in the food and pharmaceutical industries, as emulsifiers, thickeners and stabilizers, and can also be used for controlled drug release systems. In view of the above, the present work aimed to produce xanthan gum with malt bagasse (XGM) obtained from craft breweries and xanthan gum with commercial sucrose (XGSac), characterize the gums from a structural, colloidal and rheological point of view and compare them las with Sigma Aldrich® standard xanthan gum (XGS) and whey-produced xanthan gum (XGSL). Xanthan gums were produced in culture medium inoculated with Xanthomonas campestris pv. campestris, incubated at 28 °C for 120 h. The gums, after being purified with an ethanol:water mixture, were characterized by infrared spectroscopy (FTIR) and showed chemical composition and structure similar to the reference gums (XGS and XGSL). Thermal analysis (TGA and DTA) indicated that the produced gums presented different behavior from the reference gums, probably due to the incorporation of different components of the medium during the purification step. The stationary rheological characterization showed pseudoplastic behavior for all samples. In oscillatory rheology, all gums had viscoelastic network formation with formation of "weak gel". The zeta potential (ZP) of all gums was negative as a function of the anionic character, which confirmed good colloidal stability of xanthan solutions. The SDZ-Na/XGM complex (sodium sulfadiazine and xanthan gum produced with malt bagasse) showed that the compound was stable in solution and in the solid state, due to the interaction between SDZ-Na and XGM. Isothermal titration calorimetry showed that XGM has 2 sites of interaction, with stoichiometries being  0.2:1 and  2.6:1. Microbiological assays indicated that SDZ-Na, XGM and SDZ-Na/XGM were efficient to reduce, but not totally inhibit, the growth of S.aureus, P. aeruginosa, E.coli and Salmonella.