Characterization and comparison of yeasts from different sources for some probiotic properties and exopolysaccharide production

Abstract A total of 134 strains of yeasts isolated from fruits and vegetables (certain berry fruits, apples, pomegranates, carrots and grapes), free-range chicken feces and dairy products, and from 10 commercial yeast preparations were identified and subjected to analyses to determine their in vitro probiotic properties. Based on 26S rRNA sequence analysis all ten isolates from commercial products were identified as Saccharomyces cerevisiae, and the natural isolates as Candida corpophila, Candida diddensiae, Clavispora lusitaniae, Hanseniaspora opuntiae, Hanseniaspora uvarum, Kazachstania bovina, Kluyveromyces marxianus, Metschnikowia. pulcherrima, Metschnikowia sp., Meyerozyma carribbica, Pichia kluyveri and Wickerhamomyces anomalus. All isolates were found to be resistant to simulated gastric juice at pH 2.5 for 2 h and were able to grow at both 30 and 37 °C. The exopolysaccharide (EPS) production of isolates from commercial preparations and from natural sources varied between 249-275.22 and 27.95-272.22 mg/L, respectively. Two of the natural isolates had levels of EPS production comparable to the natural strains (S. cerevisiae T8-3C and S. cerevisiae P25-1) with 264.63 and 272.53 mg/L, respectively. Isolates were also investigated for autoaggregation and coaggregation abilities. The highest coaggregation ability was determined for the Saccharomyces cerevisiae P25-1 strain against Staphylococcus aureus (ATCC 25923).