Abstract
This work has evaluated the safety aspects of 20 yeast strains, isolated from food environments, selected in previous works due to their probiotic potential. Among the different strains, there are Saccharomyces and non-Saccharomyces yeasts. Before safety evaluation, differentiation of Saccharomyces cerevisiae strains was done by PCR amplification of inter-δ region with pairs of primers δ2-12 and δ12-21, which showed that they were all different from each other and also had different profiles to Saccharomyces boulardii (the only commercial probiotic yeast). The non-Saccharomyces ones were already known. The evaluation tests carried out were antibiotic and antifungal resistance, production of biogenic amines, deconjugation activity of bile salts, and different enzymatic activities: coagulase, deoxyribonuclease, hemolysin, proteolytic, and phospholipase. None of the studied strains demonstrated coagulase, hemolytic or DNase capacity (clear virulence factors), although all of them showed protease activity, some showed phospholipase activity, and half of the yeasts were capable of conjugating bile salts. Regarding antimicrobial compounds, all were resistant to antibiotics but showed sensitivity to the antimycotics used. Nevertheless, only one strain of Hanseniaspora osmophila was excluded for use in the food industry, due to its high production of tyramine.
Highlights
In Spain there is currently only one yeast strain marketed as a probiotic (CNCM I-745, Ultra-Levura), belonging to Saccharomyces boulardii species, in recent years there have been numerous research studies about probiotic capability in yeasts [1,2,3,4,5,6]
Saccharomyces boulardii CNCM I-745 was used as a positive control, since it is the only commercial probiotic yeast
The same occurred with strains 3, 127, 128, 132, and 139 whose bands obtained with the primers δ12–δ21 (Figure 2B) were very similar, but with the primer pair δ2–δ12 it was observed they were not the same strains
Summary
In Spain there is currently only one yeast strain marketed as a probiotic (CNCM I-745, Ultra-Levura), belonging to Saccharomyces boulardii species, in recent years there have been numerous research studies about probiotic capability in yeasts [1,2,3,4,5,6] These studies have shown the good probiotic potential of strains of Saccharomyces cerevisiae, Hanseniaspora osmophila, Lachancea thermotolerans, Metschnikowia ziziphicola, and Pichia kudriavzevii, among others. Researchers focus their attention on yeasts as they could offer a good alternative to probiotic bacteria for diversification of products.
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