Sugar-coated: exopolysaccharide producing lactic acid bacteria for food and human health applications

Abstract

The human enteric microbiome represents a veritable organ relied upon by the host for a range of metabolic and homeostatic functions. Through the production of metabolites such as short chain fatty acids (SCFA), folate, vitamins B and K, lactic acid, bacteriocins, peroxides and exopolysaccharides, the bacteria of the gut microbiome provide nutritional components for colonocytes, liver and muscle cells, competitively exclude potential pathogenic organisms and modulate the hosts immune system. Due to the extensive variation in structure, size and composition, microbial exopolysaccharides represent a useful set of versatile natural ingredients for the food industrial sector, both in terms of their rheological properties and in many cases, their associated health benefits. The exopolysaccharide-producing bacteria that fall within the 35 Lactobacillus and five Bifidobacterium species which have achieved qualified presumption of safety (QPS) and generally recognised as safe (GRAS) status are of particular interest, as their inclusion in food products can avoid considerable scrutiny. In addition, additives commonly utilised by the food industry are becoming unattractive to the consumer, due to the demand for a more 'natural' and 'clean labelled' diet. In situ production of exopolysaccharides by food-grade cultures in many cases confers similar rheological and sensory properties in fermented dairy products, as traditional additives, such as hydrocolloids, collagen and alginate. This review will focus on microbial synthesis of exopolysaccharides, the human health benefits of dietary exopolysaccharides and the technofunctional applications of exopolysaccharide-synthesising microbes in the food industry.

A Novel Rhamnose-Rich Hetero-exopolysaccharide Isolated from Lactobacillus paracasei DG Activates THP-1 Human Monocytic Cells

“…Among the most studied probiotics, lactic acid bacteria (LAB) possess a cell wall that is typically composed of a thick peptidoglycan layer decorated with proteins, teichoic acids, and polysaccharides (19), which can act as microbe-associated molecular patterns (MAMPs). EPSs, apart from their technological properties and industrial applications, have been found to contribute to several health-promoting features of probiotics, such as antitumor, antiulcer, immunomodulatory, antiviral, and cholesterol-lowering activities (20,21), but their mechanisms of action have not been clearly established and are probably diverse and complex.…”

Exopolysaccharides Production by Lactic Acid Bacteria

“…The HePS synthesis mechanism is more complicated. In this process, the precursor nucleotide units such as UDP-GalNac, GDP-fructose, dTDPrhamnose, UDP-galactose and UDP-glucose are synthesized intracellularly from glucose-1-phosphate and fructose-6-phosphate [22,26]. Additionally, several enzymes and/or proteins are involved in the biosynthesis and secretion of HePS.…”

“…The majority of EPSs produced by LAB are HePS, containing three to eight repeating units composed of two or more monosaccharides ( Figure 1) [22]. The HePS are produced by a great variety of mesophilic and thermophilic LAB.…”

Exopolysaccharides Produced by Lactobacillus rhamnosus KL 53A and Lactobacillus casei Fyos Affect Their Adhesion to Enterocytes

“…the extracellular glucosyltransferase or fructosyltransferase (GT) dependent pathway, and the Wzy/Wzx-dependent pathway (Ryan et al 2015). The substrate used for the synthesis of homopolysaccharides via the GT dependent pathway is sucrose or another oligosaccharide containing fructose for fructan synthesis (Galle and Arendt, 2014), and the energy used in this process derives from its hydrolysis.…”

“…Many different types of GT are encoded in the genomes of lactobacilli and only a small part of them have been biochemically characterized (van Hijum et al 2006). The GT pathway is a relatively simple enzymatic process, which requires low energy inputs (Ryan et al 2015).…”