Exploring pectinolytic yeast diversity: toward effective polygalacturonase producers for applications in wine-making.

Pectinolytic enzymes secreted by yeasts have an untapped potential in industry, particularly in wine-making. This study addresses the limitations of the current screening methods in reliably predicting the capacity of pectinolytic yeast strains to secrete polygalacturonase (PGase) under industrial conditions, suggesting a novel screening approach. Using the context of wine-making as an example, a diverse collection of 512 yeast strains from 17 species was analysed for PGase secretion, a key enzyme in pectinolysis. The traditional halo assay on solid yeast-pepton-dextrose (YPD) medium revealed 118 strains from nine genera being PGase positive. Screening these strains by incubating them at 20°C on a solid synthetic grape juice medium containing polygalacturonic acid (PG) significantly reduced the number of promising strains to 35. They belong to five genera: Kluyveromyces sp., Cryptococcus, Pichia, Torulaspora, and Rhodotorula. Afterward, a newly developed pectin-iodine assay was used to precisely quantify the PGase activity of the best-performing strains in a liquid medium. Strains from Kluyveromyces and Cryptococcus sp. stood out regarding high pectinolytic activity. Our methodological advancements tailored to identify highly promising pectinolytic yeasts for industrial use open new avenues for wine-making and other industrial processes encompassing media rich in pectin and sugars.