Production of Exopolysaccharide by Lactobacillus rhamnosus R and Analysis of Its Enzymatic Degradation during Prolonged Fermentation

Abstract

The potential of Lactobacillus rhamnosus R for producing exopolysaccharide (EPS) when grown on basal minimum medium supplemented with glucose or lactose was investigated. EPS production by L. rhamnosus R is partially growth associated and about 500 mg of EPS per liter was synthesized with both sugars. ؊1 ). It was clearly shown that the amount of EPS produced declined upon prolonged fermentation. Degradation of EPS in fermentation processes was also assessed by measuring its molecular weights and viscosities. As these reductions might have a negative effect on the yield and viscosifying properties of EPS, it was essential to examine possible causes related to this breakdown. The decrease in viscosities and molecular weights of EPS withdrawn at different cultivation times permitted us to suspect the presence of a depolymerizing enzyme in the fermentation medium. Our study on enzymatic production profiles showed a large spectrum of glycohydrolases (␣-D-glucosidase, ␤-D-glucosidase, ␣-D-galactosidase, ␤-D-galactosidase, ␤-D-glucuronidase, and some traces of ␣-L-rhamnosidase). These enzymes were localized, two of them (␣-D-glucosidase and ␤-D-glucuronidase) were partially purified and characterized. When incubated with EPS, these enzymes were capable of lowering the viscosity of the polymer as well as liberating some reducing sugars. Upon prolonged incubation (27 h), the loss of viscosity was increased up to 33%.Exopolysaccharides (EPS) produced by lactic acid bacteria (LAB) have generated increasing attention among researchers for the last few years. LAB are food-grade organisms, and the EPS that they produce contribute to the specific rheology and texture of fermented milk products. These EPS represent safe additives for novel food formulations and may have applications in nonfood products (8).There exist three important groups of EPSs produced by LAB: (i) ␣-glucans, mainly composed of ␣-1,6-and ␣-1,3-linked glucose residues, namely, dextrans produced by Leuconostoc mesenteroides subsp. mesenteroides and L. mesenteroides subsp. dextranicum and mutans produced by Streptococcus mutans and S. sobrinus; (ii) fructans, mainly composed of ␤-2,6-linked fructose molecules, such as levan produced by S. salivarius; (iii) heteropolysaccharides produced by mesophilic (Lactococcus lactis subsp. lactis and L. lactis subsp. cremoris) and thermophilic (Lactobacillus delbrueckii subsp. bulgaricus, L. helveticus, and S. thermophilus) LAB (5). The EPS produced by Lactobacillus rhamnosus belong to third group (14). The sugar composition of the EPS produced by L. rhamnosus R studied in this work, as determined on the hydrolysate by high-pressure liquid chromatography (HPLC) and by gas chromatography of the alditol acetates, is the following: Rha, 4; Glc, 2; and Gal, 1 (M. R. Van Casteren, personal communication).A considerable variation can be observed in EPS quantifications. The amount of EPS reported varies from 25 to 132 mg/ liter for L. lactis subsp. cremoris (26) Many studies showed a decrease in the total EPS amount when incuba...

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

“…The yields reduced after reaching a maximum, as many studies have reported, and this is caused by enzymes, such as glycohydorolase, produced by bacteria (Pham et al, 2000).…”

Physiological and biochemical characterization of the two α-l-rhamnosidases of Lactobacillus plantarum NCC245

“…It is also possible that L. plantarum NCC245 recycles L-rhamnose molecules from its own surface polysaccharide structures. It is known that a-L-Rhamnosidases of L. plantarum some lactobacilli degrade their own EPS structures after prolonged fermentation (Pham et al, 2000), in stationary phase, when a-L-rhamnosidase of L. plantarum NCC245 is the most active. Perpetual modification of the surface polysaccharide structures might also be a strategy of intestinal bacteria to survive the selective pressure of the adaptive immune system of the host and remain an entrenched resident of the community (Peterson et al, 2007).…”

Intermediate chains of exopolysaccharides fromLactobacillus rhamnosusRW-9595M increase IL-10 production by macrophages

“…EPSs produced by LAB are commonly used for their rheological properties, especially to improve the texture and the taste of fermented dairy products. Strain RW-9595M has also been developed in order to meet business requirements (Pham et al 2000). However, beyond these properties, the EPS produced by the bacterial strain can lead to immunomodulation that may be beneficial or not depending on the health status of the individuals who consume fermented products.…”