The potential effects of the forthcoming climate change include the rising of the average annual temperature and the accumulation of extreme weather events, like frequent and severe heatwaves, a ...phenomenon known as global warming. Temperature is an important environmental factor affecting almost all aspects of growth and development in plants. The grapevine (
spp.) is quite sensitive to extreme temperatures. Over the current century, temperatures are projected to continue rising with negative impacts on viticulture. These consequences range from short-term effects on wine quality to long-term issues such as the suitability of certain varieties and the sustainability of viticulture in traditional wine regions. Many viticultural zones, particularly in Mediterranean climate regions, may not be suitable for growing winegrapes in the near future unless we develop heat-stress-adapted genotypes or identify and exploit stress-tolerant germplasm. Grapevines, like other plants, have developed strategies to maintain homeostasis and cope with high-temperature stress. These mechanisms include physiological adaptations and activation of signaling pathways and gene regulatory networks governing heat stress response and acquisition of thermotolerance. Here, we review the major impacts of global warming on grape phenology and viticulture and focus on the physiological and molecular responses of the grapevine to heat stress.
Recent research has expanded our understanding on vineyard-associated fungal community assembly, suggesting non-random distribution and implicating regional differences in the wine
terroir
effect. ...Here, we focused on the culturable fraction of the fungal community that resides on grapes and determine wine quality, the so-called wine yeast populations. We aimed to analyze local-scale yeast community assemblages and to test whether the hypothesis of biogeographical patterns also applies to wine yeasts in particular. Surveying 34 vineyards across four main viticultural zones in Greece showed significant trends in vineyard-specific patterns. At a local scale, viticultural regions were also linked to distinct yeast community compositions. Importantly, major yeast populations directly related to wine fermentation contributed significantly to the delimitation of regions, highlighting their potential influence on the regionality of wine characteristics. In terms of the microbial
terroir
influence, yeast communities within an area were temporarily stable, which is critical for the regional character of the wine. Community structure could be explained only partially by environmental features. Maximum temperature, elevation, and net precipitation were the highest correlated variables with the yeast community biogeographic patterns. Finally, we also showed that certain environmental factors may drive the population size of specific yeast populations. The present results indicate that the wine yeast community has a geographical character at local scale, which is an important feature of the microbial
terroir
concept and thus for the wine industry.
Wine is a product of microbial activities and microbe–microbe interactions. Yeasts are the principal microorganisms responsible for the evolution and fulfillment of alcoholic fermentation. Several ...species and strains coexist and interact with their environment and with each other during the fermentation course. Yeast–yeast interactions occur even from the early stages of fermentation, determining yeast community structure and dynamics during the process. Different types of microbial interactions (e.g., mutualism and commensalism or competition and amensalism) may exert positive or negative effects, respectively, on yeast populations. Interactions are intimately linked to yeast metabolic activities that influence the wine analytical profile and shape the wine character. In this context, much attention has been given during the last years to the interactions between Saccharomyces cerevisiae (SC) and non-Saccharomyces (NS) yeast species with respect to their metabolic contribution to wine quality. Yet, there is still a significant lack of knowledge on the interaction mechanisms modulating yeast behavior during mixed culture fermentation, while much less is known about the interactions between the various NS species or between SC and Saccharomyces non-cerevisiae (SNC) yeasts. There is still much to learn about their metabolic footprints and the genetic mechanisms that alter yeast community equilibrium in favor of one species or another. Gaining deeper insights on yeast interactions in the grape–wine ecosystem sets the grounds for understanding the rules underlying the function of the wine microbial system and provides means to better control and improve oenological practices.
The performance of two potential probiotic Lactobacillus strains from olive microbiota, namely L. pentosus B281 and L. plantarum B282 was assessed as starter cultures in Spanish-style fermentation of ...heat shocked green olives cv. Halkidiki. Two different initial salt levels were studied, 10% (w/v) and 8% (w/v) NaCl, and the brines were inoculated with (a) L. pentosus B281, (b) L. plantarum B282, and (c) a mixture of both strains. A spontaneous fermentation was also taken into account as control treatment. Prior to brining, olives were heat shocked at 80°C for 10min to reduce the level of the indigenous microbiota on olive drupes and facilitate the dominance of the inoculated cultures. Microbiological, physicochemical and sensory analyses were conducted throughout fermentation. The composition of LAB population and the evolution of added inocula were assessed by Pulsed Field Gel Electrophoresis (PFGE). The final population of LAB was maintained above 6log cycles in olive flesh. Both L. pentosus B281 and L. plantarum B282 were able to dominate over indigenous LAB, albeit strain B281 exhibited higher recovery percentages (100 or 94.7% for B281 and 58.8% or 55.0% for B282 in 10% or 8% NaCl, respectively). L. pentosus B281 also dominated over L. plantarum B282, when the two strains were co-inoculated in olive fermentations. The sensory assessment showed higher preference for inoculated fermentations of L. pentosus and L. plantarum separately in 8% NaCl, followed by the L. plantarum in 10% NaCl. The present study showed that probiotic strains L. pentosus B281 and L. plantarum B282, may offer a great potential for use as functional starter cultures in olive fermentation and deliver a promising probiotic food to the consumer.
•Two potential probiotic strains of Lactobacillus were used as starters in olive fermentation.•Both strains were able to complete a normal fermentation and survive at high numbers.•L. pentosus B281 showed higher recovery rates in comparison with L. plantarum B282.•The final population of LAB at the end of the fermentation was above 6log cycles.•These strains were shown to have the potential to produce a traditional functional food.
Multi-starter wine fermentations employing non-
(NS) yeasts are becoming an emerging trend in winemaking. It is therefore important to determine the impacts of different NS strains in the wine ...phenotype and in particular the aroma outputs in different inoculation schemes and fermentation conditions. Here, two native NS yeasts,
LtMM7 and
HuMM19, were assessed for their ability to improve the quality of Moschofilero, a Greek aromatic white wine. The NS strains were initially examined in laboratory scale fermentations in mixed inoculations with ScMM23, a native
strain. LtMM7 was selected to be further evaluated in pilot scale fermentations. Five different inoculation schemes were considered: single inoculation of ScMM23 (IS), simultaneous inoculation of ScMM23 with HuMM19 (SMH) or LtMM7 (SML), and sequential inoculation of HuMM19 (SQH) or LtMM7 (SQL) followed by ScMM23. At laboratory scale fermentations, the chemical profiles were largely affected by both the NS species and the inoculation scheme applied. The sequential inoculation using HuMM19 produced the most divergent wine phenotype. However, HuMM19 caused significant increases in acetic acid and ethyl acetate levels that impeded its use in pilot scale trials. LtMM7 significantly affected the chemical profiles of wines produced at the winery, especially in the sequential inoculation scheme. Importantly, LtMM7 significantly increased the levels of acetate esters or ethyl esters, depending on the inoculation method applied. In particular, acetate esters like isobutyl acetate, hexyl acetate, and 2-phenylethyl acetate, which all impart fruity or floral aromas, were significantly increased in SQL. On the other hand, higher levels of total ethyl esters were associated with SML. The most striking differences were observed in the levels of fruit-impair esters like ethyl decanoate, 3-methylbutyl octanoate, and isoamyl hexanoate. This is the first study to report a significant increase in the ethyl ester fraction by
. Interestingly,
in SQL also increased the concentrations of damascenone and geraniol, the major teprenic compound of Moschofilero, which are associated with several typical floral and fruity aromas of the variety. Present results show that
may enhance the varietal character and increase the chemical complexity of Moschofilero wines.
Lachancea (Kluyveromyces) thermotolerans is an important member of the grape/wine yeast community with great technological potential for the wine industry. Although several molecular marker ...techniques have been developed for typing different yeast species, no one has been designed so far for L. thermotolerans. Here we present a simple and efficient method based on a multilocus SSR analysis for molecular typing and genetic diversity assessment of L. thermotolerans isolates. Following whole genome screening, five polymorphic microsatellite markers were selected and tested on a panel of grape isolates from different vineyards of two geographically separated viticultural zones, Nemea and Peza, in Greece. The SSR method proved quite discriminatory as compared to tandem repeat-tRNA-PCR, a fingerprinting method for typing non-Saccharomyces yeasts. Genetic analysis based on SSR data revealed a clear structure between the populations of the two zones. Furthermore, significant differences were also detected in a number of phenotypic characters of enological interest. A positive correlation was observed between phenotypic and genotypic diversity. Taking together, present results support the microbial terroir concept in the case of L. thermotolerans in Greece, which is an important prerequisite for the exploitation of selected genotypes as fermentation starters with region-specific characters.
A fast and simple method based on ultrasound-assisted emulsification microextraction (USAEME) was developed for the analysis of volatile compounds in wines. A full factorial 24 screening design was ...built to investigate the main factors affecting the extraction of volatile components, namely the volume of extraction solvent, sonication time, salt content, and pH. Then, the factors with significant effects were optimized using an I-optimal design. The optimal value for all the variables studied was reached under the following experimental conditions: volume of extraction solvent 200 μL and salt content 5% m/v. The suitability of the optimized method was evaluated, resulting in very good linearity with coefficients of determination (R2) higher than 0.995 in all cases, while repeatability was lower than 8.4% except for d-limonene and p-cymene. Recoveries higher than 82% were observed for the groups of ethyl esters, acetate esters, alcohols, and terpenoid alcohols (linalool, α-terpineol). The recovery of acids ranged from 70.5% to 88.9%, whereas the three monoterpenes studied (d-limonene, γ-terpinene, p-cymene) were not extracted satisfactorily. The proposed method was effectively applied for the analysis of volatile compounds in laboratory-scale fermentations with selected strains of Saccharomyces cerevisiae.
The yeast flora associated with healthy and Botrytis-infected grapes was assessed. Molecular identification methods assigned isolates to six genera and nine species. For the first time Hanseniaspora ...opuntiae was encountered as an inhabitant of the grape ecosystem. By using DraI, an informative restriction fragment length polymorphism pattern was generated to distinguish H. opuntiae from the closely related organism Hanseniaspora guilliermondii. Botrytis infection resulted in a larger population and greater diversity of yeasts enriched with fermentative or spoilage species.
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