Molecular Characterization of Successive Yeasts Strains and their Optimal Invertase Producing Conditions in Fresh Palm Wine (Raphiahookeri) Obtained from Lagos, Nigeria

Abstract

Saccharomyces cerevisiae is known to produce invertase. However, molecular characterization of successive yeast strains and their optimal invertase producing conditions in Nigerian Raphiahookeri has not been documented. In this study, molecular characterization of successive yeast strains and their optimal invertase producing conditions in fresh palm wine (Raphiahookeri) obtained from Lagos, Nigeria was evaluated. To achieve this, sequencing of 18S rDNA was carried out following DNA extraction from the yeast isolates. Invertase production within 5-day period was also monitored at different conditions for the yeast strains. The physicochemical parameters investigated include pH, optical density, titratable acidity, sugar concentration and alcohol content. Out of the 21isolates obtained, 18 were identified by 18S rDNA to beS. cerevisiae, while 3 were Penicillium chrysogenum, Blumeriagraminissp. Tritici and Fusarium culmorum. Thefungal population density decreased from 1.01 x 10⁷ to 0.9 x 10⁵CFU/ml. The pH and sugar concentration decreased with increase in age of the wine ranging from 6.05-3.33 and 3.70-1.10mg/100ml respectively. The optical density, titratable acidity and alcohol content increased with time and ranged from 0.454-0.904, 0.266-0.412 % and 0.920-5.640 % respectively. All isolates produced invertase optimally at pH 6, 30°C after 48 h incubation with S. cerevisiae CP006433.1 having the highest production (1.745U/ml).The results highlight the effect of fermentation conditions on the survival and invertase production of yeast strains in Nigerian palm wine.