Reduction of ethanol content in wine with an improved combination of yeast strains and process conditions

One interesting strategy to address the increasing alcohol content of wines, associated with climate change, is to reduce the ethanol yield during fermentation. Within this strategy, the approach that would allow the clearest reduction in alcohol content is the respiration of part of the grape sugars by yeasts. Non-Saccharomyces species can be used for this purpose but suffer from a limited ability to dominate the process and complete fermentation. In turn, Saccharomyces cerevisiae shows a high production of acetic acid under the growth conditions required for respiration. Previously proposed procedures used combinations of non-Saccharomyces and S. cerevisiae starters, or a strain of S. cerevisiae (PR1018), with unique metabolic properties. In both cases, precise management of oxygen availability was required to overcome the acetic acid problem. In this work, we have developed a laboratory scale process to take advantage of the properties of PR1018 and a strain of Metschnikowia pulcherrima. This process is more robust than the previous ones and does not rely on strict control of oxygenation or even the use of this particular strain of S. cerevisiae. Aeration can be interrupted instantly without impairing the volatile acidity. Under the selected conditions, an ethanol reduction of around 3% (v/v) was obtained compared to the standard fermentation control.The authors would like to thank Cristina Juez, Laura López, and Rufino Aguirrezábal for technical assistance. This work was funded by the Spanish Government through grant, PCI2018-092949 (ERA-CoBioTech) funded by MCIN/AEI/10.13039/501100011033 and co-funded by the European Union; and a research contract with AZ3Oeno (Spain). AMG predoctoral contract was funded by Consejería de Desarrollo Económico e Innovación de la Comunidad Autónoma de La Rioja.Peer reviewe

Understanding the transcriptomic response of Lactiplantibacillus pentosus LPG1 during Spanish-style green table olive fermentations

Lactiplantibacillus pentosus (Lbp. pentosus) is a species of lactic acid bacteria with a great relevance during the table olive fermentation process, with ability to form non-pathogenic biofilms on olive epidermis. The objective of this work is to deepen into the genetic mechanisms of adaptation of Lpb. pentosus LPG1 during Spanish-style green table olive fermentations, as well as to obtain a better understanding of the mechanisms of adherence of this species to the fruit surface. For this purpose, we have carried out a transcriptomic analysis of the differential gene expression of this bacterium during 60 days of fermentation in both brine and biofilms ecosystems. In brines, it was noticed that a total of 235 genes from Lpb. pentosus LPG1 were differentially expressed during course of fermentation and grouped into 9 clusters according to time-course analysis. Transport and metabolism of carbohydrates and amino acids, energy production, lactic acid and exopolysaccharide synthesis genes increased their expression in the planktonic cells during course of fermentation. On the other hand, expression of genes associated to stress response, bacteriocin synthesis and membrane protein decreased. A total of 127 genes showed significant differential expression between Lpb. pentosus LPG1 planktonic (brine) and sessile (biofilms) cells at the end of fermentation process (60 days). Among the 64 upregulated genes in biofilms, we found genes involved in adhesion (strA), exopolysaccharide production (ywqD, ywqE, and wbnH), cell shape and elongation (MreB), and well as prophage excision. Deeping into the genetic bases of beneficial biofilm formation by Lpb. pentosus strains with probiotic potential will help to turn this fermented vegetable into a carrier of beneficial microorganisms to the final consumers

Genome-wide identification of genes involved in growth and fermentation activity at low temperature in Saccharomyces cerevisiae

Fermentation at low temperatures is one of the most popular current winemaking practices because of its reported positive impact on the aromatic profile of wines. However, low temperature is an additional hurdle to develop Saccharomyces cerevisiae wine yeasts, which are already stressed by high osmotic pressure, low pH and poor availability of nitrogen sources in grape must. Understanding the mechanisms of adaptation of S. cerevisiae to fermentation at low temperature would help to design strategies for process management, and to select and improve wine yeast strains specifically adapted to this winemaking practice. The problem has been addressed by several approaches in recent years, including transcriptomic and other high-throughput strategies. In this work we used a genome-wide screening of S. cerevisiae diploid mutant strain collections to identify genes that potentially contribute to adaptation to low temperature fermentation conditions. Candidate genes, impaired for growth at low temperatures (12 °C and 18 °C), but not at a permissive temperature (28 °C), were deleted in an industrial homozygous genetic background, wine yeast strain FX10, in both heterozygosis and homozygosis. Some candidate genes were required for growth at low temperatures only in the laboratory yeast genetic background, but not in FX10 (namely the genes involved in aromatic amino acid biosynthesis). Other genes related to ribosome biosynthesis (SNU66 and PAP2) were required for low-temperature fermentation of synthetic must (SM) in the industrial genetic background. This result coincides with our previous findings about translation efficiency with the fitness of different wine yeast strains at low temperature.Funding from the Spanish Government trough MINECO and FEDER funds: MINECO AGL2012-32064 and AGL2015-63629-R grants, INIA RM2012-00007-00-00 grant, MINECO RTC-2014-2186-2 and MINECO PCIN-2015-143 grants is acknowledged.Peer reviewe

Identifying the Main Drivers in Microbial Diversity for Cabernet Sauvignon Cultivars from Europe to South Africa: Evidence for a Cultivar-Specific Microbial Fingerprint

Microbial diversity in vineyards and in grapes has generated significant scientific interest. From a biotechnological perspective, vineyard and grape biodiversity has been shown to impact soil, vine, and grape health and to determine the fermentation microbiome and the final character of wine. Thus, an understanding of the drivers that are responsible for the differences in vineyard and grape microbiota is required. The impact of soil and climate, as well as of viticultural practices in geographically delimited areas, have been reported. However, the limited scale makes the identification of generally applicable drivers of microbial biodiversity and of specific microbial fingerprints challenging. The comparison and meta-analysis of different datasets is furthermore complicated by differences in sampling and in methodology. Here we present data from a wide-ranging coordinated approach, using standardized sampling and data generation and analysis, involving four countries with different climates and viticultural traditions. The data confirm the existence of a grape core microbial consortium, but also provide evidence for country-specific microbiota and suggest the existence of a cultivar-specific microbial fingerprint for Cabernet Sauvignon grape. This study puts in evidence new insight of the grape microbial community in two continents and the importance of both location and cultivar for the definition of the grape microbiome.The YeSViTE project (FP7-IRSES-2013-GA612441) supported the secondments of J.T. and F.V. to the Stellenbosch University (South Africa) and R.F. to the Agrarian University of Georgia (Georgia), and the grape sampling in Tuscany carried out by D.F. This work was also supported by Winetech grant SU IWBT 16-02

Genetic Improvement of Wine Yeasts

In recent years, wine market is undergoing a change due to the ever-growing request to improve the sensory features and nutritional properties of the final product. Most wine production is based on the use of starter cultures consisting of selected strains of Saccharomyces cerevisiae, able to ensure quick and controlled fermentations. However, the reduced number of really different starters can lead to a wine standardization resulting in flattening of taste. Moreover, there is a still growing request of winemaking process innovation of the and, in this sense, yeasts can play a central role. In order to gain innovative characteristics, the research relies on the isolation and selection of new oenological strains of S. cerevisiae and non-Saccharomyces species showing interesting metabolic or technological features, or on the improvement of wine yeasts at genetic level. In the case of the latter approach, examples to obtain both non-Genetically Modified (GM) and GM organisms (GMO) are available in literature. In this chapter we discuss the significant developments of the genetic engineering based on standard homologous integration, the inter and intraspecific hybridization in wine yeasts, the use of random mutagenesis, the foundation of the experimental evolution strategy and we describe the CRISPR/Cas9 genome editing approach that has been revolutionizing the field of biotechnology

Une souche de saccharomyces cerevisiae et son utilisation pour la production de vin à teneur réduite en alcool

The present invention relates to a novel Saccharomyces cerevisiae strain which presents low acetic acid yield under aerobic fermentation processes. This feature makes it especially useful for reducing the ethanol content of wines, while avoiding excess volatile acidity associated to other isolates of the same species, by providing sufficient oxygen during alcoholic fermentation. In contrast to strains from other yeast species, this strain is capable of driving wine fermentation to dryness. In this way the process is performed with the inoculation of a single S. cerevisiae yeast strain. The present invention also relates to the use and method for fermented beverage production, particularly production of quality wines with reduced ethanol content.NoConsejo Superior de Investigaciones Científicas (CSIC)A1 Solicitud de patente con informe sobre el estado de la técnic