Exopolysaccharide-producing lactic acid bacteria isolated from traditional Algerian dairy products and their application for skim-milk fermentations

摘要

Exopolysaccharide (EPS)-producing lactic acid bacteria are used in the dairy industry to obtain products with appropriate sensorial properties. Specific EPS act as stabilizers, thickeners, and/or fat-replacers, and are considered as natural biopolymers. The autochthonous microbiota of foods provides a rich reservoir of biodiversity to find biopolymers for novel applications. In this study, a collection of LAB isolated from homemade Algerian dairy products was screened for a rational selection of EPS-producing strains. Six isolates, identified as Lactobacillus plantarum, presented a stable mucoid/ropy phenotype after several sub-cultivations and they were used to ferment skimmed milk. Those fermented with strains LBIO1 and LBIO28 had higher viscosity, a smooth/creamy texture and presented lower syneresis. The kinetics of growth and EPS-production, followed for 48 h, showed that both strains had similar behaviour, the molar mass (about 2 x 10(6) Da) and radius of gyration (about 80 nm) of the polymers being also similar. However, LBIO28 was able to increase the apparent viscosity of the fermented milk to a higher extent than LBIO1, which could be related with the earlier accumulation of EPS in the first strain in relation to the gelation point. Thus, these two ropy EPS-producing strains are suitable for different applications in dairy fermentations.