Invited Review: Methods for the Screening, Isolation, and Characterization of Exopolysaccharides Produced by Lactic Acid Bacteria

Abstract

The ability to produce exopolysaccharides (EPS) is widespread among lactic acid bacteria (LAB), although the physiological role of these molecules has not been clearly established yet. Some EPS confer on LAB a "ropy" character that can be detected in cultures that form long strands when extended with an inoculation loop. When EPS are produced in situ during milk fermentation they can act as natural biothickeners, giving the product a suitable consistency, improving viscosity, and reducing syneresis. In addition, some of these EPS may have beneficial effects on human health. The increasing demand by consumers of novel dairy products requires a better understanding of the effect of EPS on existing products and, at the same time, the search for new EPS-producing strains with desirable properties. The use of genetically modified organisms capable of producing high levels of EPS or newly designed biopolymers is still very limited. Therefore, exploration of the biodiversity of wild LAB strains from natural ecological environments is currently the most suitable approach to search for the desired EPS-phenotype. The screening of ropy strains and the isolation and characterization of EPS responsible for this characteristic have led to the application over the past years of a wide variety of techniques. This review summarizes the available information on methods and procedures used for research on this topic. The information provided deals with methods for screening of EPS-producing LAB, detection of the ropy phenotype, and the physicochemical and structural characterization of these molecules, including parameters related to their viscosifying properties. To our knowledge, this is the first compilation of methods available for the study of EPS produced by LAB.

Isolation, characterization and localization of extracellular polymeric substances from the cyanobacteriumArthrospira platensisstrain MMG-9

“…Xylose has also been reported as an important component of EPS (Filali Mouhim et al, 1993;Trabelsi et al, 2009), supporting our finding of the large proportion of this sugar in the TEPS of A. platensis (23%), although previous studies of TEPS have not reported the rare sugar ribose as was found in this study. Confocal laser scanning microscopy provided information with regard to the localization of EPS and supported the view that the different operational EPS fractions could indeed be related to recognizable structures (Ruas-Madiedo & de los Reyes-Gavilan, 2005). The use of various fluorescently labelled lectins and fluorescent stains gave insight into the localization of the EPS (Strathmann et al, 2002) and autofluorescence of the cyanobacteria visualized the cells (Ahmed et al, 2011).…”

Exopolysaccharides producing Lactobacillus fermentum strain for enhancing rheological and sensory attributes of low-fat dahi

“…Besides acting as biothickening agents, some EPS produced by LAB have showed beneficial effects on human health (Chabot et al 2001). Production of EPS varies from strain to strain and depends on various factors like composition of the medium, age of the cell, pH and temperature (De Vuyst et al 2003; Ruas-Madiedo and de los Reyes-Gavilan 2005). Bacterial cell produces capsular polysaccharides associated with the cell surface and/or ropy polysaccharides in the fermentation medium (Sutherland 1972).…”

An alternative method for screening lactic acid bacteria for the production of exopolysaccharides with rapid confirmation

“…The total number of EPS produced by the microorganisms is strongly influenced by the sugar present in the medium. However, there are some kinds of sugar that are better for the production of EPS because the production of the polymer depends on the strain tested and thus on the enzymatic metabolism of each strain (RUAS-MADIEDO; REYES-GAVILÁN, 2005).…”

“…EPS associated with bacterial cells are responsible for the formation of mucous colonies in solid medium or for the formation of long filaments when the colony is extended with an inoculation loop (RUAS-MADIEDO; REYES-GAVILÁN, 2005). In liquid medium, EPS can be detected by the high resistance…”