engleski

Oenological characterization of non-Saccharomyces yeasts isolated from Croatian white grape variety Maraština

Wine is the result of alcoholic fermentation carried out principally by Saccharomyces cerevisiae strains which transform sugars present in grape must into ethanol, CO2 and other compounds. Differently from S. cerevisiae which is scarcely present on harvested grapes, non- Saccharomyces yeasts are highly abundant which gives them the opportunity to begin fermentation. Since use of commercial yeasts may negatively affect the aromatic complexity of wine, new trends in winemaking have emphasised the concept of microbiological terroir thus stimulating the use of indigenous starters from different regions, including non-Saccharomyces yeasts aimed to increase organoleptic complexity of wines. This study focused on the oenological characterization of non- Saccharomyces yeasts isolated from 11 Maraština vineyards located within the Croatian coastal winegrowing region of Dalmatia aimed to discover new candidate strains for development as starter cultures. Among the 257 isolates, 27 different species from 16 genera were identified by sequencing the ITS1-5.8S-ITS2 region. The species from Aureobasidium genus (Aureobasidium pullulans, Aureobasidium melanogenum, and Aureobasidium namibiae) largely prevailed, followed by Metschnikowia chrysoperlae, Hanseniaspora uvarum and Lachancea thermotolerans strains. All isolates were evaluated for their ethanol and SO2 resistance, ability to grow on different temperatures, H2S and acetic acid production, as well as hydroxycinnamic acid decarboxylase (HCDC) activity. Furthermore, the 75 best performing strains were screened for the activity of 19 enzymes using API-ZYM test system with the emphasis on the enzymes related to wine aroma such as esterase, esterase lipase, lipase, leucine acrylamidase, valine acrylamidase, cystine acrylamidase, and β-glucosidase. Various strains from Lachancea, Hanseniaspora, Metschnikowia, Pichia, Hyphopichia and Starmerella genera showed high SO2 (up to 250 mg/L) and ethanol (up to 12%) tolerance, low acetic acid and medium-low H2S production. The HCDC activity was detected in several Metschnikowia and Aureobasidium isolates. Most of the isolates demonstrated high leucine and valine acrylamidase activity whereas several Hanseniaspora uvarum, Lachancea thermotolerans and Metschnikowia chrysoperlae strains were characterized by high β- glucosidase activity thus allowing the selection of the most promising strains for further development as starter cultures to produce aromatically distinct wines.

non-Saccharomyces yeasts ; Maraština ; isolation ; characterisation

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