Influence Of Vanillin in Exopolysaccharide Production in Lactic Acid Bacteria

DIAZ VERGARA, L.I.; BETTIOL, M. R.; BINETTI, A. G.; MONTENEGRO, M. A.

Congreso; XVII Congreso Argentino de Microbiología General; 2022

The exopolysaccharides (EPS) are polymers of high molecular weight produced by microorganisms. The EPS produced by lactic acid bacteria (LAB) are quite interesting for food applications. This EPS have been studied for their beneficial applications to human health thanks to their antimicrobial, anticancer, anticholesterol, antioxidant activity, immunomodulatory, and prebiotic properties. Vanillin is an organic compound used as a flavoring agent in food, beverages, and pharmaceutics. This work aims to evaluate the influence of vanillin in the production and antioxidant activity of EPS in three LAB strains (M023, M024, and M030) isolated in our laboratory. To evaluate the influence of vanillin the EPS selection medium (skim milk 5% w/v, yeast extract 0.35% w/v, peptone 0.35 w/v, and sucrose 5% w/v) was supplemented with vanillin (V) to obtain a concentration of 0.001% v/v, a control (C) without the addition of vanillin was used. The bacteria strains (previously grown in De Man, Rogosa and Sharpe broth for 48 h at 37°C) were inoculated to V and C, and incubated for 48 h at 37°C in microaerophilia. For the EPS purification, the proteins were precipitated with trichloroacetic acid 4% w/v and centrifugated at 10000 g for 20 min at 4°C. The pellets were resuspended in distilled water and dialyzed against distilled water through a dialysis membrane with molecular weight cutoff of 12–14 kDa for 96 h at 4 °C. The solid content was determined in a thermogravimetric balance. The EPS content was determined by the phenol-sulfuric method, to 0.5 mL of sample is added 1 mL of phenol 5% w/v, later 2.5 mL of sulfuric acid 98%. After 5 min of reaction, the absorbance at 492 nm of the samples as well as standard sugar glucose (10 to 100 μg/mL) was read by spectrophotometry. The antioxidant activity was determined by the deactivation of the cation ABTS at different EPS concentrations, measured at 734 nm with a spectrophotometer, the final antioxidant activity was expressed as Trolox equivalent antioxidant capacity (TEAC, ug of Trolox equivalent to 1 ug of EPS). The results show that vanillin did not have an effect on the EPS production levels (average of 2 g/L). However, the antioxidant activity was increased for the strains M023 and M024 from 0.006 and 0.010 ugTrolox/ugEPS to 0.009 and 0.023 ugTrolox/ugEPS, respectably, and decreased the activity for M030. Vanillin has antimicrobial activity, although, the tested concentrations did not have an inhibitory effect on the growth of the bacteria, but did have an effect on the EPS characteristics. In conclusion, vanillin did present an influence on the antioxidant activity of the EPS obtained; but did not present an influence on the production levels. Future studies should focus on the characterization of the obtained EPS with the different cultural conditions.