Abstract
BackgroundLactic acid bacteria (LAB) are known to have a significant ability to colonize the human intestinal tract and adhere to the surface of intestinal epithelial cells. Among the various lactic acid bacteria, exopolysaccharide (EPS) producing strains are known to provide a variety of health benefits for their hosts (e.g. anti-inflammatory, antioxidant, antitumor and stress tolerant effects). Recently, EPSs and EPS-producing lactic acid cultures have gained interest within the food industry and are playing important roles as biothickeners and texturizing agents due to their hydrocolloidal nature. In this study, 156 lactic acid bacterial strains isolated from fecal samples of healthy young children were screened and evaluated for active EPS-production capability.ResultsAmong the various human origin lactic acid flora isolated, Weissella confusa VP30 showed the highest EPS productivity and its EPS producing properties were characterized under various cultural conditions in this research. To document the safety of W. confusa VP30, antibiotic resistance, hemolytic, and ammonia production properties were evaluated in addition. No significant negative results were observed. The maximum EPS production by W. confusa VP30 was 59.99 ± 0.91 g/l after 48 h of cultivation in media containing 10% sucrose, far exceeding EPS production by other bacterial strains reported elsewhere. Based on gel permeation chromatography (GPC), the molecular weight of EPS produced by W. confusa VP30 was 3.8 × 106 Da. Structural analysis of the released EPS fraction by 13C and 1H nuclear magnetic resonance (NMR) spectroscopy revealed that W. confusa VP30 can produce dextran with glucose units linked with 96.5% α (1 → 6) glycosidic bonds and 3.5% α (1 → 3) branches.ConclusionThe high EPS production capability and safety of W. confusa VP30 justify food industry consideration of this cell strain for further evaluation and potential industrial use.
Highlights
Numerous Lactic acid bacteria (LAB) genera, including Carnobacterium, Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Oenococcus, Pediococcus, Streptococcus, Tetragenococcus, Vagococcus and Weissella sp. have been isolated from a variety of human, animal, plant and environmentalJin et al Microb Cell Fact (2019) 18:110 grow even further due to increased consumer interest in health and expanding consumer income
Among LAB strains, human origin LAB strains have shown high resistance to gastric juice and bile as well as high survival rates in the gastrointestinal tract, due to their ability to adhere to the surface of intestinal epithelial cells [8, 9]
Selection of high EPS‐producing cell strains Multiple groups have screened and identified LAB capable of producing EPSs by cell and colony phenotypes in solid medium. This visual cell classification tool has been widely used for many years to identify EPS producing LAB from naturally occurring microbiota as a preselection process
Summary
Numerous LAB genera, including Carnobacterium, Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Oenococcus, Pediococcus, Streptococcus, Tetragenococcus, Vagococcus and Weissella sp. have been isolated from a variety of human, animal, plant and environmentalJin et al Microb Cell Fact (2019) 18:110 grow even further due to increased consumer interest in health and expanding consumer income. Among LAB strains, human origin LAB strains have shown high resistance to gastric juice and bile as well as high survival rates in the gastrointestinal tract, due to their ability to adhere to the surface of intestinal epithelial cells [8, 9]. Multiple researchers have demonstrated the diverse biofunctionalities (e.g. anti-allergic effects, anticancer properties, bacteriocin production, high transmission rates and high adherence ability) of human origin LAB and their metabolic substances through in vitro and in vivo experiments [10,11,12,13,14]. Lactic acid bacteria (LAB) are known to have a significant ability to colonize the human intestinal tract and adhere to the surface of intestinal epithelial cells. Among the various lactic acid bacteria, exopolysaccharide (EPS) producing strains are known to provide a variety of health benefits for their hosts (e.g. anti-inflammatory, antioxidant, antitumor and stress tolerant effects). 156 lactic acid bacterial strains isolated from fecal samples of healthy young children were screened and evaluated for active EPS-production capability
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