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Isolation and structural characterization of levan produced by probiotic Bacillus tequilensis-GM from Tunisian fermented goat milk

Abid, Yousra, Azabou, Samia, Casillo, Angela, Gharsallah, Houda, Jemil, Nawel, Lanzetta, Rosa, Attia, Hamadi, Corsaro, Maria Michela
International journal of biological macromolecules 2019 v.133 pp. 786-794
Enterococcus, Escherichia coli, Listeria monocytogenes, amylases, antibiotics, beta-galactosidase, bile salts, biofilm, fermented dairy products, gastric juice, goat milk, hemolysis, hydrophobicity, levan, molecular weight, probiotics, proteinases, saliva, skim milk, starter cultures
The probiotic features of strain GM newly isolated from Tunisian spontaneously fermented goat milk and identified as Bacillus tequilensis-GM were assessed. Strain GM showed high resistance to saliva (90.64%), gastric juice (88.55%), intestinal juice (72.83%) and resistance to bile salts (65.22%), was able to act against Listeria monocytogenes ATCC 15313, Escherichia coli ATCC 25922 and Enterococcus feacalis ATCC 25912, showed high surface hydrophobicity (77.3%) and was sensitive to most of the studied antibiotics. Strain GM did not exhibit any hemolytic activity whereas it was able to produce protease, amylase and β-galactosidase. Moreover, results showed that strain GM produced high molecular weight β-(2 → 6)-levan with high ability to inhibit and to disrupt pathogenic biofilms and with high ability to reduce syneresis of sucrose-supplemented skimmed milk. B. tequilensis-GM can therefore be suitable to be used as starter culture in fermented dairy products, since it possesses desirable probiotic properties in addition to its ability to produce levan.