Biodiversity and Enological Potential of Non-Saccharomyces Yeasts from Nemean Vineyards

Aspasia Nisiotou,Georgios Sgouros,Georgios Banilas,Athanasios Mallouchos,Ioanna Chalvantzi,Yiannis Paraskevopoulos

doi:10.3390/fermentation4020032

Abstract

Vineyards in Nemea, the most important viticultural zone in Greece, were surveyed for indigenous non-Saccharomyces (NS) yeasts of enological potential. NS populations were isolated from the final stage of alcoholic fermentation and identified by a range of molecular methods. The enological profiles of Hanseniaspora guilliermondii, H. osmophila, Lachancea thermotolerans, Starmerella bacillaris and Torulaspora delbrueckii strains were evaluated. Significant interspecies variation was observed in fermentation kinetics. H. osmophila and T. delbrueckii showed the highest capacity for prompt initiation of fermentation, while S. bacillaris achieved a higher fermentation rate in the second half of the process. Significant differences were also observed in the chemical parameters of NS strains. S. bacillaris SbS42 and T. delbrueckii TdS45 were further evaluated in mixed-culture fermentations with Saccharomyces cerevisiae. NS strains achieved lower population densities than S. cerevisiae. SbS42 exhibited a higher death rate than TdS45. The chemical profiles of different ferments were separated by principal component analysis (PCA). Both NS strains were associated with lower levels of ethanol, when compared to single S. cerevisiae inoculation. TdS45 increased the ethyl acetate levels, while SbS42 caused a different production pattern of higher alcohols. This is the first report to explore the enological potential of NS wine yeast populations from Nemea. Based on prominent enological traits identified, the selected S. bacillaris and T. delbrueckii strains may be further exploited as co-culture starters for improving the quality and enhancing the regional character of local wines.

Highlights

The alcoholic fermentation of grape must is principally conducted by Saccharomyces cerevisiae, the major wine yeast
In various later studies it has been shown that several NS species, such as I. occidentalis, L. thermotolerans, M. pulcherrima, Starmerella bacillaris and Z. bailii, were able to maintain high viable populations for longer periods than previously thought and were even isolated from the final stages of the alcoholic fermentation [4,7,10,11]
Organic acids, sugars, glycerol and ethanol were determined by high-performance liquid chromatography (HPLC) with refractive index detection according to OIV-MA-AS313-04, slightly modified [18]

Summary

Introduction

The alcoholic fermentation of grape must is principally conducted by Saccharomyces cerevisiae, the major wine yeast. In various later studies it has been shown that several NS species, such as I. occidentalis, L. thermotolerans, M. pulcherrima, Starmerella bacillaris (synonym C. zemplinina) and Z. bailii, were able to maintain high viable populations (up to 6–7 log CFU/mL) for longer periods than previously thought and were even isolated from the final stages of the alcoholic fermentation [4,7,10,11] These species may play a crucial role in winemaking, due to the production of important metabolites that shape the flavor and contribute to the style of wines [1,12]. The respective wine phenotypes were characterised through chemical analysis and compared

Materials and Methods

Molecular Identification of Yeasts

Pure-Culture Fermentations

Mixed-Culture Fermentations

Statistical Analysis

Results and Discussion

Technological Characterization of NS Yeast Strains

Principal characteristics of of non-Saccharomyces

Chemical

Chemical Profiles of Wines Produced in Mixed-Culture Fermentations

Conclusions