Abstract

Genetic diversity and pectinolytic activity of epiphytic yeasts from grape carposphere

The genetic diversity of epiphytic yeasts from grape carposphere is susceptible to environmental variations that determine the predominant carposphere microbiota. Understanding the diversity of yeasts that inhabit grape carposphere in different environments and their pectinolytic activity is a way to understand the biotechnological potential that surrounds us and help improve winemaking. Therefore, this study aimed to evaluate the pectinolytic activity and characterize the genetic diversity of isolated epiphytic yeasts from grape carposphere. Grapes of the Bordeaux cultivar were collected from different regions of Paraná and Rio Grande do Sul States, in Brazil, and the yeasts were isolated from these grape carpospheres. Monosporic isolates were morphologically and genetically characterized on potato dextrose agar medium and by PCR-RFLP and rep-PCR (BOX-PCR) in the ITS1-5.8S-ITS2 region of rDNA. The index of pectinolytic activity of isolates was also evaluated estimating the ratio between the halo diameter of enzymatic degradation and the diameter of the colony when the isolates were grown in cultivation medium containing 10 g/L pectin, 5 g/L yeast extract, 15 g/L agar, 0.12% (w/v) Congo red, and pH 6.2. We observed that the grape carposphere is an environment with a great genetic diversity of epiphytic yeasts of the following genera: Cryptococcus (31.25%), Pichia (25.0%), Candida (25.0%), Dekkera (12.5%), and Saccharomyces (6.25%). The PCR-RFLP technique allowed analyzing existing polymorphism among individuals of a population based on a more restrict and evolutionarily preserved region, mostly utilized to differentiate isolates at the genus level. Approximately 33% of yeast isolates presented pectinolytic activity with potential biotechnological for wine and fruit juice production. This great genetic variability found indicated that it is a potential reservoir of genes to be applied in viniculture improvement programs.

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