Introduction In the Yaghnob Valley in Tajikistan lives an isolated human population, who still utilize ancient fermentation methods to produce fermented milk as one of their main foods. The area is very isolated, so theinhabitants and their diet have remained protected without influence or contamination from the surroundingworld. Thus, it is interesting to study the microbial biodiversity of their fermented food.The aim of the present work is thephenotypic characterization of yeasts isolated from Yaghnobi fermented milk. Materials and Methods Thirty yeast isolates were obtained from the original Yaghnobi fermented milk and from the sameone reproduced at home for three years.The isolation was performed on M17, MRS, WL,YPD and YPD plus chloramphenicol. Phenotypic characterization were assessed by growth i) on different carbon sources, ii) in presence of ox bile, iii) at high temperatures, iv) in acidic condition and v) in presence of hydrogen peroxide. Also the invasiveness in YPD and hyphae formation was studied. Results The 30 yeast strains, belonging to Kluyveromyces marxianus, Pichia fermentans, Saccharomyces cerevisiae plus one Kazachstania unispora and one Kluyveromyces lactis. revealed different phenotypes within the same species; e.g. invasiveness from 0 to 3 among the isolates of both S. cerevisiae and P. fermentans, the latter species also showed large variations in thermo-tolerance (inhibition from 40°Cto 46°C), and varying tolerance to acidic conditions. Only the strain of K. lactis and about 50%of K .marxianus strains grew at 46°C. All strains of K. marxianus grew at ox bile up to 2%. Of the S. cerevisiae strains, 50% grew in ox bile up to 2%, while two strains were inhibited already at 0.5%. Conclusions The data obtained suggest the presenceof yeasts with interesting probiotic properties in Yaghnobi fermented milk, such as the ability to survive in harsh gastrointestinal environment. The complete probiotic characterization of these yeasts will be investigated further.
Qvirist, L., Strati, F., De Filippo, C., Modesto, M., Andlid, T., Mattarelli, P., et al. (2015). Phenotypic Characterization of Yeasts Isolated from Yaghnobi Fermented Milk.
Phenotypic Characterization of Yeasts Isolated from Yaghnobi Fermented Milk
MODESTO, MONICA MARIANNA;MATTARELLI, PAOLA;
2015
Abstract
Introduction In the Yaghnob Valley in Tajikistan lives an isolated human population, who still utilize ancient fermentation methods to produce fermented milk as one of their main foods. The area is very isolated, so theinhabitants and their diet have remained protected without influence or contamination from the surroundingworld. Thus, it is interesting to study the microbial biodiversity of their fermented food.The aim of the present work is thephenotypic characterization of yeasts isolated from Yaghnobi fermented milk. Materials and Methods Thirty yeast isolates were obtained from the original Yaghnobi fermented milk and from the sameone reproduced at home for three years.The isolation was performed on M17, MRS, WL,YPD and YPD plus chloramphenicol. Phenotypic characterization were assessed by growth i) on different carbon sources, ii) in presence of ox bile, iii) at high temperatures, iv) in acidic condition and v) in presence of hydrogen peroxide. Also the invasiveness in YPD and hyphae formation was studied. Results The 30 yeast strains, belonging to Kluyveromyces marxianus, Pichia fermentans, Saccharomyces cerevisiae plus one Kazachstania unispora and one Kluyveromyces lactis. revealed different phenotypes within the same species; e.g. invasiveness from 0 to 3 among the isolates of both S. cerevisiae and P. fermentans, the latter species also showed large variations in thermo-tolerance (inhibition from 40°Cto 46°C), and varying tolerance to acidic conditions. Only the strain of K. lactis and about 50%of K .marxianus strains grew at 46°C. All strains of K. marxianus grew at ox bile up to 2%. Of the S. cerevisiae strains, 50% grew in ox bile up to 2%, while two strains were inhibited already at 0.5%. Conclusions The data obtained suggest the presenceof yeasts with interesting probiotic properties in Yaghnobi fermented milk, such as the ability to survive in harsh gastrointestinal environment. The complete probiotic characterization of these yeasts will be investigated further.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
