Characterization of yeasts isolated from traditional kefir grains for potential probiotic properties

Abstract

Kefir is a mixed fermented product with numerous attributed health benefits due to presence of a complex culture composed of bacteria and yeasts in an exopolysaccharide matrix. This work aimed at isolating and identifying culturable yeast species from two types of traditional kefir grains and establishing some potential probiotic properties including survival in the gastrointestinal tract, auto-aggregation, hydrophobicity and hydrolytic enzymes production. All the isolates showed good survival rates in simulated gastrointestinal tract solution, with <0.5 log10 reduction. Kluyveromyces lactis was characterized with a high level of hydrophobicity (88.75%) but moderate auto-aggregation whereas S. unisporus showed moderate hydrophobicity and auto-aggregation. Indicator enteric bacteria adhered onto both viable and non-viable yeast isolates and controls. In comparison to Saccharomyces boulardii strains used as controls, both kefir yeast strains showed low alpha hemolytic and proteolytic activities, but exhibited no phospholipase activity. Kluyveromyces lactis and Saccharomyces unisporus isolated, were identified on the basis of 26s rDNA and ITS region sequencing. Overall, the yeast isolates showed some potential probiotic properties.

Identification and Growth Characterization of a Novel Strain of Saccharomyces boulardii Isolated From Soya Paste

“…The cell hydrophobic and autoaggregation properties in the intestinal epithelial cells are considered as a probiotic criterion. The S. boulardii showed a good hydrophobic affinity and autoaggregation ability increases over time, which matches the previous study result (19,43).…”

“…According to the result of the test (Figure 2D), the isolate was growing up to 8.0% NaCl concentration, but there was a rapid decrease in growth after 3.0% NaCl concentration (25). Simulated gastrointestinal juice tolerance is considered one of the major criteria for probiotics, which is a primary barrier against most ingested microorganisms (19,43). The current results thus revealed that the S. boulardii strain exhibited strong resistance to gastric juice (Figure 3) in pH 3.0 and almost 80% of cells successfully survived, with some previous study data strongly supporting the results (5,9,18).…”

Inhibitory Effect of Depolymerized Sulfated Galactans from Marine Red Algae on the Growth and Adhesion of Diarrheagenic Escherichia coli

“…Adhesion of bacteria onto yeast cells was performed as previously described [46], with some modification. Briefly, the cultured yeast and ETEC K88 in suspensions was harvested by centrifugation at 8000 rpm/min for 10 min, respectively.…”

Characterization of Sporidiobolus ruineniae A45.2 Cultivated in Tannin Substrate for Use as a Potential Multifunctional Probiotic Yeast in Aquaculture

“…Cell surface hydrophobicity is defined as a nonspecific interaction in adhesion between probiotic microorganisms onto GIT epithelial cells, where they may provide prophylactic and therapeutic benefits [ 20 ]. Colonization in the intestinal epithelial cell wall and mucosal surfaces can prevent pathogenic bacteria adhesion and inflammatory reactions [ 21 ].…”

“…Auto-aggregation is defined as aggregation among yeast cells to form flocs and colonize the intestinal environment of the host when the cells approach harmful conditions [ 20 , 23 ]. Probiotic microorganisms should be associated with higher auto-aggregation than pathogenic microorganisms [ 22 ], specifically Strep.…”