Isolation of novel homopolysaccharide-producing lactic acid bacteria from Romanian raw milk and fermented dairy products

Abstract

Traditionally fermented foods can be a rich source of diverse lactic acid bacteria (LAB) with interesting functional properties, such as exopolysaccharide (EPS) production. The objectives of this study were to map the mucoid and/or ropy LAB isolated from raw milk and traditionally fermented dairy products, collected in different regions of Romania, to study the species diversity within the samples and to further explore the EPS-producing capacity of the isolates. Seventy-three LAB strains were isolated and identified through (GTG)5-PCR genomic fingerprinting and SDS-PAGE of whole-cell proteins. Lactococcus lactis was the most frequently encountered species, followed by Lactobacillus plantarum, Leuconostoc spp., and Enterococcus spp. Nine strains produced homopolysaccharides (HoPS, glucose monomers), namely L. lactis 1.8; Leuc. citreum 1.10, 1.11, 1.12, 2.8, and 4.11; Leuc. mesenteroides 21.2; Leuc. pseudomesenteroides 20.6; and Weisella confusa/cibaria 38.2, six of them in the concentrations above 10 g/L, both in milk and MRS medium supplemented with sucrose. In all EPS, the glucose constituents were connected by different α-linkages, among which α-1,6-linkages were the most prevalent.