Microbial Terroir in Chilean Valleys: Diversity of Non-conventional Yeast.

Carla Jara,Albert Mas,V Felipe Laurie,Jaime Romero

doi:10.3389/fmicb.2016.00663

Carla Jara, Albert Mas + Show 2 more

Open Access

https://doi.org/10.3389/fmicb.2016.00663

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Abstract

In this study, the presence of non-conventional yeast associated with vineyards located between latitudes 30°S and 36°S was examined, including the valleys of Limarí, Casablanca, Maipo, Colchagua, Maule, and Itata. The microbial fingerprinting in each valley was examined based on the specific quantification of yeast of enological interest. Grape–berries were sampled to evaluate the presence and load of non-conventional yeast with enological potential, such as Metschnikowia, Hanseniaspora, Torulaspora, Debaryomyces, Meyerozyma, and Rhodotorula. These yeasts were present in all vineyards studied but with varying loads depending on the valley sampled. No identical fingerprints were observed; however, similarities and differences could be observed among the microbial profiles of each valley. A co-variation in the loads of Metschnikowia and Hanseniaspora with latitude was observed, showing high loads in the Casablanca and Itata valleys, which was coincident with the higher relative humidity or rainfall of those areas. Non-conventional yeasts were also isolated and identified after sequencing molecular markers. Potentially good aromatic properties were also screened among the isolates, resulting in the selection of mostly Metschnikowia and Hanseniaspora isolates. Finally, our results suggest that microbial terroir might be affected by climatic conditions such as relative humidity and rainfall, especially impacting the load of non-conventional yeast. In this study, the microbial fingerprint for yeast in Chilean vineyards is reported for the first time revealing an opportunity to study the contribution of this assembly of microorganisms to the final product.

Highlights

Grape–berries are a great reservoir for microorganisms such as yeasts, lactic acid bacteria, and acetic acid bacteria
Hanseniaspora and Metschnikowia were present in Limarí, Casablanca, and Itata valleys at comparatively high loads with respect to Maipo and Maule valleys
The following three sets of yeast showed load patterns that were similar across valleys: Hanseniaspora and Metschnikowia; Torulaspora, Saccharomyces, and Meyerozyma; and Rhodotorula and Debaryomyces (Figure 2)

Summary

Introduction

Grape–berries are a great reservoir for microorganisms such as yeasts, lactic acid bacteria, and acetic acid bacteria. Yeasts play a fundamental role in the process of alcoholic fermentation because they are responsible for the transformation of sugars into ethanol, carbon dioxide, and other metabolites (Ribereau-Gayon et al, 2006). Due to their role in alcoholic fermentation, in enology, yeasts are usually divided into two categories: Saccharomyces and non-Saccharomyces. The latter category includes a wide array of different genera, termed non-conventional yeasts. Saccharomyces has a high fermentative capacity and predominates during alcoholic fermentation (Ribereau-Gayon et al, 2006), whilst non-conventional yeasts proliferate during the first stage of spontaneous fermentation as they can tolerate low concentrations of ethanol, approximately 4% v/v (Fleet, 1993).

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