Screening, Extraction and Characterization of EPS from Lactic Acid and Related Bacteria Isolated from Poultry Environment

EMMERT, GERMAN; ARGAÑARAZ MARTÍNEZ, ELOY; GRANDE, SONIA; SAGUIR, FABIANA; PÉREZ CHAIA, ADRIANA

Córdoba

Congreso; XVII Congreso Argentino de Microbiología General; 2022

Sociedad Argentina de Microbiología General - SAMIGE

As biologically synthesized macromolecules, exopolysaccharides (EPSs) are loosely bound to the bacterial cell wall or dispersed in their environment during the growth phase of microorganisms. Depending on the diversity of monosaccharide subunits and their biosynthetic pathways, are classified into homopolysaccharides (HoPSs) and heteropolysaccharides (HePSs). EPSs from LAB have been reported to have antioxidant, prebiotic, antibacterial, antibiofilm activities and other properties related to their chemical structure. The aim of this investigation was the screening of different strains of LAB, as well as bifidobacteria and propionibacteria (some of them already tested as probiotics in previous works) for the production, extraction and structural study of their EPSs. A total of twenty two strains, isolated from the poultry environment, were studied in modified MRS agar medium (Lactobacillus, Enterococcus, Pediococcus, Bifidobacterium genera) or LAPT agar medium (Acidipropionibacterium genus). All media were supplemented with one of three different sugars (glucose, lactose or sucrose) as carbon sources. As result of this screening, only 4 strains of Lactobacillus genus, Ligilactobacillus salivarius LET201, Limosilactobacillus reuteri LET210, Limosilactobacillus vaginalis LET 202 and LET203, produced mucoid colonies on sucrose medium. The EPSs production at different sucrose concentration (2, 5, 15 and 25%), initial pH (6.5, 5.5 and 4.5) and temperature (24, 37 and 41 °C) was later studied in the modified MRS agar. It was concluded that the best conditions for EPSs production were 5% sucrose, initial pH 6.5, and incubation at 37°C for 48 hours, which were used to develop the strains in broth medium. EPSs were obtained after centrifugation, proteins remotion, and precipitation with chilled ethanol. The precipitates were resuspended, dialyzed with ultrapure water and lyophilized. The EPSs obtained from the 4 strains, evidenced similar spectra when analyzed using Raman spectroscopy. The EPS analysis of one of these strains, Ligilactobacillus salivarius LET201, was complemented with FTIR and NMR spectra analysis. Results of these studies suggested that the EPS of this strain is composed of glucose monomers (glucan), linearly linked by α-(1→6) linkages. In previous investigations, Ligilactobacillus salivarius LET201 evidenced interesting probiotic properties for chicken protection against the intestinal epithelium damage caused by dietary lectins. The EPS production and its nature, encourage the study of other possible functional properties of this strain, especially effects on the immune system and antimicrobial properties, which are actually in course.