Abstract

In this study, a total of 9 morphologically and biochemically different yeast species were isolated from Nigerian fermented food product, ‘ogi’. These yeast species were screened for probiotic properties such as antibacterial activities, acid and bile tolerance. Six species out of the yeast isolates that survived pH 2 were grown in 0.3% bile salts which were monitored by spectrophotometer for 5 h. Three yeast species with the highest growth performance measured by increment in optical density were identified as Pichia kudriavzevii by sequencing the conserved (D1/D2) region of 16S rDNA. Among the three selected strains, isolate MH458240 (M9) showed the highest acid tolerance of 5.80±0.20 log cfu/ml while isolate MH458239 (M5) manifested the least acid tolerance of 3.80±0.20 log cfu/ml. At 0.3% bile salts concentration, isolate MH458239 (M5) demonstrated the highest growth rate of 1.110±011. The antibacterial activities of the three selected yeast strains were also determined. While isolates MH458240 (M9) and MH458239 (M5) inhibited the growth of the tested pathogens, isolate MH458238 (M4) could not inhibit the growth of any of the pathogens used. Out of the three strains of P. kudriavzevii used, isolate MH458240 (M9) which demonstrated the best overall probiotic potential was found to contain only three open reading frames (ORF) while the two other isolates contained five. Isolate MH458240 (M9) was found to be in a complete different cluster from the two other strains.

Key words: Yeasts, fermented food, Pichia kudriavzevii, probiotic properties, open reading frames (ORF).