Use of non-saccharomyces Torulaspora delbrueckii yeast strains in winemaking and brewing

Selected Saccharomyces yeast strains have been used for more than 150 years in brewing and for several decades in winemaking. They are necessary in brewing because of the boiling of the wort, which results in the death of all yeast cells, with the exception of some Belgian style beers (ex. Lambic), where the wort is left to be colonized by indigenous yeast and bacteria from the environment and ferment naturally. In winemaking their use is also pertinent because they provide regular and timely fermentations, inhibit the growth of indigenous spoilage microorganisms and contribute to the desired sensory characters. Even though the use of selected Saccharomyces strains provides better quality assurance in winemaking in comparison to the unknown microbial consortia in the must, it has been debated for a long time now whether the use of selected industrial Saccharomyces strains results in wines with less sensory complexity and “terroir” character. In previous decades, non-Saccharomyces yeasts were mainly considered as spoilage/problematic yeast, since they exhibited low fermentation ability and other negative traits. In the last decades experiments have shown that there are some non-Saccharomyces strains (Candida, Pichia, Kluyveromyces, Torulaspora, etc) which, even though they are not able to complete the fermentation they can still be used in sequential inoculation-fermentation with Saccharomyces to increase sensory complexity of the wines. Through fermentation in a laboratory scale, we have observed that the overall effects of selected Torulaspora delbrueckii yeast strains, is highly positive, leading to products with pronounced sensory complexity and floral/fruity aroma in winemaking and brewing

Influence of sodium chloride on wine yeast fermentation performance

This paper concerns research into the influence of salt (sodium chloride) on growth, viability and fermentation performance in a winemaking strain of the yeast, Saccharomyces cerevisiae. Experimental fermentations were conducted in both laboratory-scale and industrial-scale experiments. Preculturing yeasts in elevated levels of sodium chloride, or salt “preconditioning” led to improved fermentation performance. This was manifest by preconditioned yeasts having an improved capability to ferment high-sugar containing media with increased cell viability and with elevated levels of produced ethanol. Salt-preconditioning most likely influenced the stress-tolerance of yeasts by inducing the synthesis of key metabolites such as trehalose and glycerol. These compounds may act to improve cells’ ability to withstand osmostress and ethanol toxicity during fermentations of grape must. Industrial-scale trials using salt-preconditioned yeasts verified the benefit of this novel physiological cell engineering approach to practical winemaking fermentations

A New Tool for the Quantification of Microorganism Interaction Dynamics

A two-reservoir, membrane bioreactor for carrying out studies of mixed population dynamics in batch fermentation is presented. Mixing requirements and design aspects for the validity of the approach are presented and discussed. Equations describing mixing times between the reservoirs are given and compared to the experimental results. The validity of the approach is demonstrated by the study of several types of situations in the bioreactor. The main validation consists of the comparison between the results obtained in an actual mixed culture and the results obtained by keeping the strains separated. Finally, this new tool is used to study the interaction kinetics between two oenological bacteria. These experiments in liquid media help to determine the seeding conditions for a chosen strain to overgrow another strain through a quantification of the interaction dynamics

Correlation of Wine’s Main Components’ Concentration with the Density of Model Aqueous Solutions and Wine Samples

Density is an important physical property, affecting wine mouthfeel, while it can also be used for monitoring alcoholic fermentation in winemaking. Aim of this study was to elucidate the correlation of ethanol, glucose/fructose, glycerol and tartaric acid on the density of model aqueous solutions and Greek wine samples. Various model aqueous solutions were prepared and density was measured at 20 ˚C. Density of dry white and red wine samples was also measured. A linear regression analysis was performed and theoretical fermentation monitoring curves by density measurement were obtained. The resulting models presented a coefficient of determination over 97.3%. Tartaric acid was found to increase density the most, followed by glucose and glycerol, whereas ethanol decreased density. The knowledge of the correlation of the concentration of each wine component with density may be beneficial to quantitative analysis of wine and to optimizing wine mouthfeel

Un nouvel outil d'étude quantitative des interactions microbiennes en milieu liquide ; application aux bactéries lactiques œnologiques

Pour la quantification des interactions lors de cultures mixtes, la connaissance de la concentration cellulaire de chacune des composantes de la culture est indispensable. La numération différentielle de ces composantes est délicate et impose souvent le recours a des méthodes complexes. Ce constat nous a conduit a proposer un réacteur spécifique a l'étude des interactions entre micro-organismes en milieu liquide : le principe consiste a maintenir séparées les souches concernées de part et d'autre d'une membrane qui permet par ailleurs le libre échange des substrats et métabolites. Le réacteur est constitué de deux réservoirs connectés par un faisceau de fibres creuses immergé dans l'un d'eux. Le mouvement du milieu et ainsi le mélange des solutés est induit au travers de la membrane par une surpression exercée alternativement dans chacun des réservoirs. Ainsi chacune des souches se développe dans un espace séparé, mais dans un milieu commun, et l'évolution de sa concentration peut être suivie par l'une ou l'autre des méthodes classiques appliquées en culture pure (numération, nephélométrie...). La capacité de mélange a été validée : l'appareillage satisfait aux conditions de mélange requises par les vitesses de réaction microbienne. Par la suite, nous nous sommes intéressés aux interactions lors de cultures mixtes de bactéries lactiques du genre Œnococcus. Les interactions observées sur milieu gélose ont pu être précisées et cet appareillage en a permis une quantification rigoureuse; il a aussi permis d'évaluer quantitativement l'influence de variables comme le rapport de population au temps initial de la culture. Enfin, un modèle mathématique de quantification de ces interactions est proposé

Alleviation of stuck wine fermentations using salt-preconditioned yeast

The influence of salt (sodium chloride) on the cell physiology of wine yeast was investigated. Cellular viability and population growth of three wine-making yeast strains of Saccharomyces cerevisiae, and two non-Saccharomyces yeast strains associated with wine must microflora (Kluyveromyces thermotolerans and K. marxianus) were evaluated following salt pre-treatments. Yeast cells growing in glucose defined media exposed to different sodium chloride concentrations (4, 6 and 10% w/v) exhibited enhanced viabilities compared with nontreated cultures in subsequent trial fermentations. Salt ‘preconditioning’ of wine yeast seed cultures was also shown to alleviate stuck and sluggish fermentations at the winery scale, indicating potential benefits for industrial fermentation processes. It is hypothesized that salt induces specific osmostress response genes to enable yeast cells to better tolerate the rigours of fermentation, particularly in high sugar and alcohol concentrations

Étude des intéractions entre micro-organismes du vin (du qualitatif au quantitatif)

Pour une bonne maîtrise du procédé de vinification il est important de connaître d'une part, les caractéristiques cinétiques et métabolites des souches pures des micro-organismes mis en oeuvre et, d'autre part, les relations pouvant exister entre ces différentes familles. C'est sur ce dernier point que porte l'essentiel de ce travail. Nous avons étudié les interactions entre les levures Saccharomyces cerevisiae de la fermentation alcoolique et les bactéries lactiques Oenococcus oeni de la fermentation malolactique (FML) par des tests qualitatifs en milieu gélosé et des tests quantitatifs en cultures consécutives dans un milieu liquide synthétique et dans du vin. Pour les interactions levure-bactéries les tests en milieu gélosé ne se sont pas avérés assez discriminatoires. Les tests en milieu liquide synthétique bien qu'ils mettent en évidence les antagonismes entre deux micro-organismes ne sont pas toujours représentatifs des interactions obtenues dans le vin. Les tests en milieu naturel sont la meilleure approche mais pas la solution absolue car d'un milieu naturel à l'autre l'extrapolation reste difficile. Concernant les interactions entre bactéries lactiques de l'espèce Oenococcus oeni nous avons réalisé et comparé les résultats des tests qualitatifs en milieu gélosé et des cultures mixtes en milieu liquide. Les problèmes de quantification lors des cultures mixtes ont été résolus par l'utilisation d'un bioréacteur à membranes à deux compartiments. Le rôle de la membrane est de séparer les souches tout en permettant l'homogénéisation du milieu pour qu'elles soient soumises au même environnement. Les résultats montrent que le choix du couple levure-bactérie est très important pour une bonne réalisation de la FML car des phénomènes d'inhibition des bactéries par les levures sont fréquemment observés. Pour les cultures mixtes de bactéries des phenomènes d'inhibition ont été mis en évidence mais ils se manifestent sous différentes formes.TOULOUSE-ENSIACET (315552325) / SudocSudocFranceF

The effect of preconditioning cells under osmotic stress on high alcohol production

This paper focuses on the research into the influence of salt on physiology of the yeast, Saccharomyces cerevisiae. Specifically, the work focused on how NaCl affected the growth, viability and fermentation performance of this yeast in laboratory-scale experiments. One of the main findings of the research presented involved the influ­ence of salt “preconditioning” of yeasts which represents a method of pre-culturing of cells in the presence of salt in an attempt to improve subsequent fermentation performance. Such an approach resulted in preconditioned yeasts having an improved capability to ferment high-sugar containing media (up to 60% w/v of glucose) with increased cell viability and with increased levels of produced ethanol (higher than 20% in vol.). Salt-preconditioning was most likely influencing the stress-tolerance of yeasts by inducing the synthesis of key metabolites such as trehalose and glycerol which act to improve cells’ ability to withstand osmostress and ethanol toxicity. The industrial-scale trials using salt-preconditioned yeasts verified the benefit of the physiological engineering approach to practical fermentations. Overall, this research has demonstrated that a relatively simple method designed to adapt yeast cells physiologically - by salt-preconditioning - can have distinct advantages for al­cohol fermentation processes

Measuring Wine Quality and Typicity

Wine quality and typicity are complex concepts that can be hard to define. Wine is a product destined to not only be consumed and appreciated but also marketed, and its distinctiveness, quality and typicity are important characteristics that describe a wine’s sensory profile and, ultimately, add value to the finished product. Even though both quality and typicity are mostly assessed using a sensory evaluation, many studies have examined the feasibility of using chemical analysis methods in order to increase the objectivity of assessments. Today, the use of chemometrics facilitates the handling of big data, and outcomes from various analytical techniques can be integrated to produce more accurate results. This study discusses the existing sensory and analytical approaches, implications and future prospects for an objective measurement of quality and typicity as well as methods for the selection of appropriate data for predictive model development