Growth Associated Exopolysaccharide Expression in Lactococcus lactis subspecies cremoris Ropy352

Abstract

A natural lactococcal isolate, Lactococcus lactis ssp. cremoris Ropy352, has been previously shown to express two phenotypically distinct exopolysaccharides (ropy and mucoid). This natural isolate was cultured on various media to explore the carbon requirements for exopolysaccharide expression. Ropy exopolysaccharide expression was optimal when grown in defined media rather than on M17-based media. Ropy352 was examined for inducible lysogenic phages. No lytic burst was observed in Ropy352 with ultraviolet light or mitomycin C for phage induction. The sugar compositions of the two phenotypically distinct exopolysaccharides were determined. The ropy exopolysaccharide is composed of galactose and glucose in the molar percents of 42 and 58%, respectively. The mucoid exopolysaccharide is composed of galactose, glucose, and mannose in the molar percents of 58, 29, and 13%, respectively. Mutational analysis revealed that mutations impairing ropy exopolysaccharide expression but not affecting mucoid exopolysaccharide expression could be isolated.

Production of Exopolysaccharide by Lactobacillus plantarum and the Prebiotic Activity of the Exopolysaccharide

“…Galactose and rhamnose, however, were not involved in the EPS production by strain 301102S; glucose and mannose were involved. There are no data in the literature regarding metabolic routes that could explain the incorporation of mannose units in EPSs produced by LAB, although the presence of this sugar has been already described (Sanchez et al, 2006;Knoshaug et al, 2000;Aslim et al, 2006). Some authors suggest that the detection of sugars such as mannose, arabinose, or xylose can be attributed to contamination from material coming from medium components such as yeast extract (Sanchez et al, 2006).…”

Isolation and Characterization of Lactic Acid Bacteria Strains from Raw Camel Milk for Potential Use in the Production of Yogurt

“…Exopolysaccharides production: The cultures were streaked on modified MRS (m-MRS; glucose replaced with 100g/l sucrose) [36] and incubated at the optimum growth temperature for 24h, then tested for slime formation using the inoculated loop method [37]. Formed colonies were dragged up using a metal loop and the strains were considered positively slimy producer if the length of slime was above 1.5mm [35].…”

Identification and Molecular Characterization of the Chromosomal Exopolysaccharide Biosynthesis Gene Cluster from Lactococcus lactis subsp. cremoris SMQ-461

“…Some LAB are also able to produce exopolysaccharides (EPS), which are either excreted in the growth medium as slime (ropy form) or remain attached to the bacterial cell wall forming capsular EPS (6,32). In the dairy industry, EPS-producing LAB, including the genera Streptococcus, Lactobacillus, and Lactococcus, are used in situ to improve the textural characteristics of fermented dairy products, especially low-fat yoghurt and cheese.…”

“…EPS-producing LAB, including strains of Lactococcus spp., have been shown to express at least two distinct phenotypic forms of EPS, either ropy and/or capsular forms (32). Moreover, they produce EPS with considerable diversity in structure and composition (14,54,55,58,64).…”