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Characterization of a bovine isolate Lactobacillus mucosae DPC 6426 which produces an exopolysaccharide composed predominantly of mannose residues

London, L. E., Price, N. P., Ryan, P., Wang, L., Auty, M. A., Fitzgerald, G. F., Stanton, C., Ross, R. P.
Journal of Applied Microbiology 2014 v.117 pp. 509-517
Lactobacillus mucosae, atomic force microscopy, bile, cattle, chemical residues, exopolysaccharides, fermentation, galactose, gastric juice, glucose, heat stress, heat tolerance, hydrochloric acid, mannose, microarray technology, mucosa, phenotype, probiotics, ribosomal RNA, scanning electron microscopy, sequence analysis, sodium chloride
Aim: Identification of exopolysaccharide (EPS)-producing lactobacilli as EPS production is potentially a very important trait among probiotic lactobacilli from technological and health promoting perspectives. Methods and Results: Characterization of EPS-producing Lactobacillus mucosae DPC 6426 in detail based on 16S rRNA sequencing, sugar fermentation analysis, phenotypic microarray technology and EPS production using scanning electron and atomic force microscopy. The EPS was found to consist of mannosyl residues, with mannose, glucose and galactose found to be the major sugar residues present in an approximate ratio of 3: 2: 2. The strain was compared to non-EPS-producing Lb. mucosae DPC 6420 following exposure to salt, bile, acid and heat stresses. Lb. mucosae DPC 6426 exhibited 2-fold increased (p< 0.05) survival during 120 min exposure to 5M NaCl, 3-fold increased survival during 90 min exposure to 0.7% (w/v) bile (p< 0.05), 3-fold increased survival when exposed to simulated gastric juice (p< 0.001) for 10 min and 5-fold increased survival during 60 min exposure to HCl (p< 0.01) compared with Lb. mucosae DPC 6420. Furthermore, Lb. mucosae DPC 6426 was found to be more heat tolerant (p< 0.001) compared with Lb. mucosae DPC 6420 during 30 min exposure to 55°C. Conclusion: These data indicate that the EPS-producing Lb. mucosae DPC 6426 exhibits technological and biological robustness compared to a non-EPS-producing Lb. mucosae strain. Impact of Study: The data implicates the potential suitability of EPS-producing Lb. mucosae DPC 6426 in food applications, and/or as a probiotic culture.