Production of exopolysaccharides by Lactobacillus and Bifidobacterium strains of human origin, and metabolic activity of the producing bacteria in milk

Abstract

This work reports on the physicochemical characterization of 21 exopolysaccharides (EPS) produced by Lactobacillus and Bifidobacterium strains isolated from human intestinal microbiota, as well as the growth and metabolic activity of the EPS-producing strains in milk. The strains belong to the species Lactobacillus casei, Lactobacillus rhamnosus, Lactobacillus plantarum, Lactobacillus vaginalis, Bifidobacterium animalis, Bifidobacterium longum, and Bifidobacterium pseudocatenulatum. The molar mass distribution of EPS fractions showed 2 peaks of different sizes, which is a feature shared with some EPS from bacteria of food origin. In general, we detected an association between the EPS size distribution and the EPS-producing species, although because of the low numbers of human bacterial EPS tested, we could not conclusively establish a correlation. The main monosaccharide components of the EPS under study were glucose, galactose, and rhamnose, which are the same as those found in food polymers; however, the rhamnose and glucose ratios was generally higher than the galactose ratio in our human bacterial EPS. All EPS-producing strains were able to grow and acidify milk; most lactobacilli produced lactic acid as the main metabolite. The lactic acid-to-acetic acid ratio in bifidobacteria was 0.7, close to the theoretical ratio, indicating that the EPS-producing strains did not produce an excessive amount of acetic acid, which could adversely affect the sensory properties of fermented milks. With respect to their viscosity-intensifying ability, L. plantarum H2 and L. rhamnosus E41 and E43R were able to increase the viscosity of stirred, fermented milks to a similar extent as the EPS-producing Streptococcus thermophilus strain used as a positive control. Therefore, these human EPS-producing bacteria could be used as adjuncts in mixed cultures for the formulation of functional foods if probiotic characteristics could be demonstrated. This is the first article reporting the physicochemical characteristics of EPS isolated from human intestinal microbiota.

Sugar source modulates exopolysaccharide biosynthesis in Bifidobacterium longum subsp. longum CRC 002

“…This study presents a potentially new EPS isolated from B. longum subsp. longum CRC 002 with a proposed repeating unit composition of 2 galactose : 3 glucose, which is different from other excreted EPS characterized from B. longum (Abbad Andaloussi et al, 1995;Roberts et al, 1995;Salazar et al, 2009) as well as from B. pseudocatenulatum (Salazar et al, 2009). The EPS composition among B. longum subsp.…”

“…Only 17 % of lactobacilli and bifidobacterial strains isolated from human gastrointestinal microbiota showed EPS production by phenotypic methods (Ruas-Madiedo et al, 2007). Bifidobacterium longum strain YIT4028 has been reported to have cell wall polysaccharides consisting of rhamnogalactan (Nagaoka et al, 1995), while three out of four EPSs characterized from B. longum also contained rhamnose (Salazar et al, 2009). More recently, the EPS repeating unit from B. longum strain JBL05 was shown to be a heptasaccharide containing glucose, galactose and rhamnose (Kohno et al, 2009).…”

Isolation and Characterization of Exopolysaccharide-Producing Lactobacillus plantarum SKT109 from Tibet Kefir

“…Hi gh molecular weight of EPS contributed to limiting the susceptibility to syneresis and improving the texture of fermented milk by cross-linking of the EPS into a network structure with the proteins during fermentation [Hassan et . The difference in molecular weights of the EPSs could be attributed to the different producing strains, the culture media, and the growth conditions used [Salazar et al, 2009].…”

“…Li et al [2014c] also reported that soymilk fermented with EPS-producing L. plantarum 70810 had more characteristic flavor compounds and lower beany flavor compounds than those in the original soymilk base. The EPS-producing Lactobacillus strains were not found to produce excessive amount of disgusting flavor compounds when used in fermented milks [Salazar et al, 2009]. Additionally, fermented milk fermented with EPS-producing S. thermophilus 05-34 exhibited significantly higher scores on sensory property than the fermented milk containing non-EPS-producing S. thermophiles 05-32 [Qin et al, 2011].…”

“…Streptococci [Purohit et al, 2009], lactobacilli [Folkenberg et al, 2006], lactococci [Ayala-Hernández et al, 2009] and bifidobacterium [Prasanna et al, 2013] are some EPS-producing bacterial species which have been successfully used to produce fermented milk with varying improvement of physicochemical and biological properties. The EPS--producing Lactobacillus plantarum H2 was shown to increase the viscosity of stirred, fermented milks to a similar extent as the EPS-producing Streptococcus thermophilus strain [Salazar et al, 2009]. Another EPS-producing strain of S. thermophilus 1275 was capable of improving the consistency, but reducing the firmness and spontaneous whey separation of low-fat yogurt, and the EPS showed a protective effect on the survival of L. delb rueckii ssp.…”