Purpose: The purpose of this study was to assess, on the laboratory scale, the probiotic potential and technological characteristics of 50 yeast strains, previously isolated from spontaneously fermented Greek natural black table olives.
Methods: All yeast strains were studied for their survival in conditions simulating the passage through the human gastrointestingal tract. The estimation of the survival was performed by enumeration of viable colonies on Yeast –Mold agar, before and after incubation in synthetic gastric and pancreatic juice. Furthermore, enzymatic activities were determined using the API-ZYM test (bio-Mérieux) according to the instructions of the manufacturer. Finally, the resistance to different salt concentrations under diverse pH values was assessed by estimating the non-inhibitory and minimum inhibitory concentration values (NIC, MIC) by spectrophotometry.
Results: From the total number of the studied yeast isolates, 23 strains (> 70%) showed a high rate of survival under the simulation of gastric and pancreatic digestion. Moreover, a strain belonging to Saccharomyces cerevisiae showed a survival rate up to 90% in the overall digestion. All strains showed lipolytic and proteolytic properties; whereas, 27 strains exhibited β-glucosidase activity and 14 strains exhibited α-glycosidase activity. For the three estimated pH values (3.5, 5.0 and 6.5), NIC median values were 4.8, 6.1 and 7.7, respectively, and MIC values were 10.9, 13.3, and 11.6, respectively.
Significance: These data suggest the potential use of yeasts as probiotics to enhance the potential of fermented table olives as functional food.