Exopolissacarídeos de bactérias ácido láticas : otimização da produção em meio soro de leite, caracterização parcial e avaliação do potencial antioxidante in vitro

Abstract

The present work focused on production, characterization, and determination of antioxidant effects of exopolysaccharides (EPS) produced by lactic acid bacteria cultivated in cheese whey. A total of 64 strains of lactic acid bacteria isolated from “coalho” cheese were tested to select the strain with appreciable amounts of EPS. After selection, the strain was identified by molecular methods. The temperature, pH and fermentation time influence were evaluated to determine the optimal conditions for EPS production in cheese whey medium. The EPS obtained was also partially characterized and evaluated at concentrations from 0.2 to 2 mg/mL for the antioxidant effect against DPPH, ABTS, hydroxyl and superoxide radicals. As a result, the selected strain (133v) showed concentration of 5.58 mg/mL The genotyping test revealed the Enterococcus faecium species. With the statistical experimental design was possible to find the optimal conditions to EPS production which the temperature was found to be 42 °C and fermentation time of 22 h. Under these conditions, was obtained 21.74 mg/mL of EPS. The partial characterization of EPS revealed the presence of functional groups such as hydroxyl, amine, carboxyl, proteins, and uronic acid. The in vitro antioxidant assay of the EPS showed good scavenging effects on DPPH, ABTS and superoxide radicals with maximal capacity of 27%, 72,20% and 43,23%, respectively. However, the hydroxyl radical was reduced by EPS from the concentration of 2 mg/mL with 1.29%. In conclusion, this work showed that was possible to obtain a natural biopolymer with potential application in the food industry through the fermentation of a low-cost, nutritionally rich and abundant medium.