Identification of Yeasts with Mass Spectrometry during Wine Production

The aim of the present study was to identify yeasts in grape, new wine “federweisser” and unfiltered wine samples. A total amount of 30 grapes, 30 new wine samples and 30 wine samples (15 white and 15 red) were collected from August until September, 2018, from a local Slovak winemaker, including Green Veltliner (3), Mūller Thurgau (3), Palava (3), Rhein Riesling (3), Sauvignon Blanc (3), Alibernet (3), André (3), Blue Frankish (3), Cabernet Sauvignon (3), and Dornfelder (3) grapes; federweisser and unfiltered wine samples were also used in our study. Wort agar (WA), yeast extract peptone dextrose agar (YPDA), malt extract agar (MEA) and Sabouraud dextrose agar (SDA) were used for microbiological testing of yeasts. MALDI-TOF Mass Spectrometry (Microflex LT/SH) (Bruker Daltonics, Germany) was used for the identification of yeasts. A total of 1668 isolates were identified with mass spectrometry. The most isolated species from the grapes was Hanseniaspora uvarum, and from federweisser and the wine—Saccharomyces cerevisiae.

Microbiota of different wine grape berries

The wine grape berries share a complex microbial ecology including filamentous fungi, yeasts and bacteria. The microbiota reveals different physiological characteristics and depends on the grape ripening stage and the availability of nutrients with different effect on wine production. The microbiota of grape berries (n = 12) was isolated and identified in the present study. The samples were collected in September 2018. Grape berries were obtained from Vrbovo vineyard located in Slovakia. The grape berries investigated belonged to Blue Frankish, Cabernet Sauvignon, Chardonnay, Dornfelder, Feteasca regala, Green Veltliner, Irsai Oliver, Mūller Thurgau, Pálava, Pinot Blanc, Rhinriesling and Welschriesling varieties. The microorganisms were cultivated on Malt extract agar (MEA) at 25 °C for five days in aerobically for microscopic filamentous fungi and Tryptone Soya agar (TSA) at 37 °C for 24 – 48 h aerobically for bacteria and yeasts. Total bacterial counts on different wine grape berries ranged from 2.57 ±0.09 in Chardonnay to 4.39 ±0.21 log CFU.g-1 in Pálava. Microscopic filamentous fungi count ranged from 1.18 ±0.03 in Blue Frankish to 2.60 ±0.17 log CFU.g-1 in Welschriesling. MALDI-TOF MS Biotyper mass spectrometry was used for identification of microorganisms (bacteria and yeasts) and microscopic filamentous fungi with manuals. The most identified microscopic fungal species was Alternaria sp., for yeasts Issatchenkia orientalis and Leuconostoc mesenteroides subsp. mesenteroides for bacteria.

Bacteria and yeasts isolated from different grape varieties

The aim of this study was to isolate and identify bacteria and yeasts in different grape samples. The samples were collected in September 2017. Used 13 grape samples in this study (9 white and 4 red) were from the local Slovak winemakers. Alibernet, Irsai Oliver, Dornfelder, Blue Frankish, Feteasca regala, Green Veltliner, Pálava, Mūller Thurgau, Rhinriesling, Cabernet Savignon, Pinot Blanc, Savignon Blanc and Welschriesling. Two cultivation media were used for detection of bacteri and yeasts in grape samples. Malt extract agar base (MEA) and Tryptone Soay agar (TSA) were used for the cultivation of bacteria and yeasts. Cultivation was performed by spread plate method. Ethanol/formic acid extraction procedure was used for preparation of samples. MALDI-TOF Mass Spectrometer (Microflex LT/SH) (Bruker Daltonics, Germany) was used for identification of bacteria and yeasts. In total, 8 genera of yeasts, 8 genera of Gram-negative bacteria and 10 of Gram-positive bacteria were identified. Together 333 isolates, yeasts, Gram-negative and Gram-positive bacteria were identified.