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The yeast Candida zemplinina (Starmerella bacillaris) is frequently isolated from grape and wine environments. Its enological use in mixed fermentation with Saccharomyces cerevisiae has been extensively investigated these last few years, and several interesting features including low ethanol production, fructophily, glycerol and other metabolites production, have been described. In addition, molecular tools allowing the characterization of yeast populations have been developed, both at the inter- and intraspecific levels. However, most of these fingerprinting methods are not compatible with population genetics or ecological studies. In this work, we developed 10 microsatellite markers for the C. zemplinina species that were used for the genotyping of 163 strains from nature or various enological regions (28 vineyards/wineries from seven countries). We show that the genetic diversity of C. zemplinina is shaped by geographical localization. Populations isolated from winemaking environments are quite diverse at the genetic level: neither clonal-like behaviour nor specific genetic signature were associated with the different vineyards/wineries. Altogether, these results suggest that C. zemplinina is not under selective pressure in winemaking environments.

Alcoholic fermentation of grape must is a complex process, involving several yeast genera and species. The early stages in fermentation are dominated by non-Saccharomyces yeasts that are gradually replaced by the Saccharomyces cerevisiae species, which takes over the fermentation. Quantitative studies have reported the influence of non-Saccharomyces yeast species on wine quality and evaluated their biotechnological interest. The industrial yeast market, which, until recently, exclusively focused on S. cerevisiae, now offers S. cerevisiae/non-Saccharomyces (including Torulaspora delbrueckii) multi-starters. The development of these new mixed industrial starters requires a better understanding of the interaction mechanisms between yeast populations in order to optimize the aromatic impact of the non-Saccharomyces yeast while ensuring complete alcoholic fermentation thanks to S. cerevisiae. For this purpose, a new double-compartment fermentor was designed with the following characteristics: (1) physical separation of two yeast populations, (2) homogeneity of the culture medium in both compartments, (3) fermentation kinetics monitored by weight loss due to CO2 release, and (4) independent monitoring of growth kinetics in the two compartments. This tool was used to compare mixed inoculations of S. cerevisiae/T. delbrueckii with and without physical separation. Our results revealed that physical contact/proximity between S. cerevisiae and T. delbrueckii induced rapid death of T. delbrueckii, a phenomenon previously described and attributed to a cell-cell contact mechanism. In contrast, when physically separated from S. cerevisiae, T. delbrueckii maintained its viability and its metabolic activity had a marked impact on S. cerevisiae growth and viability. The double fermentor is thus a powerful tool for studying yeast interactions. Our findings shed new light on interaction mechanisms described in microorganism populations.

The aim of this work was to study the volatile thiol productions of two industrial strains of Torulaspora delbrueckii and Saccharomyces cerevisiae during alcoholic fermentation (AF) of Sauvignon Blanc must. In order to evaluate the influence of the inoculation procedure, sequential and simultaneous mixed cultures were carried out and compared to pure cultures of T. delbrueckii and S. cerevisiae. The results confirmed the inability of T. delbrueckii to release 4-methyl-4-sulfanylpentan-2-one (4MSP) and its low capacity to produce 3-sulfanylhexyl acetate (3SHA), as already reported in previous studies. A synergistic interaction was observed between the two species, resulting in higher levels of 3SH (3-sulfanylhexan-1-ol) and its acetate when S. cerevisiae was inoculated 24 h after T. delbrueckii, compared to the pure cultures. To elucidate the nature of the interactions between these two species, the yeast population kinetics were examined and monitored, as well as the production of 3SH, its acetate and their related non-odorous precursors: Glut-3SH (glutathionylated conjugate precursor) and Cys-3SH (cysteinylated conjugate precursor). For the first time, it was suggested that, unlike S. cerevisiae, which is able to metabolize the two precursor forms, T. delbrueckii was only able to metabolize the glutathionylated precursor. Consequently, the presence of T. delbrueckii during mixed fermentation led to an increase in Glut-3SH degradation and Cys-3SH production. This overproduction was dependent on the T. delbrueckii biomass. In sequential culture, thus favoring T. delbrueckii development, the higher availability of Cys-3SH throughout AF resulted in more abundant 3SH and 3SHA production by S. cerevisiae.

Summary -In order to check the reliability of micrometeorological and chamber methods for the measurement of N 2 O fluxes at the 'soil-atmosphere' interface, an experiment using these two methodologies was performed in autumn on a bare soil fertilized with 150 kg N-NH 4 NO 3 ha -1 . Micrometeorological measurements were continuously taken using either the gradient or eddy correlation methods, the N 2 O gas mixing ratio being measured with a tunable diode laser absorption spectrometer. N 2 O emission fluxes were also monitored in two automatic chambers during two 3-h periods every day, ie, around midday and midnight, whereas 16 manual chambers were monitored only around midday. Areas over which the fluxes were measured ranged from 0.18 and 0.49 m 2 for the manual and automatic chambers, respectively, to more than 10 4 m 2 for the micrometeorological methods. Additional soil variables were obtained, including the soil bulk density profile, water content, temperature and N-NO 3 -and N-NH 4 + concentrations. The different methods provided similar estimates of N 2 O fluxes with an average over the whole of the common measurement period of around 6 ng N-N 2 O m -2 s -1 . The 16 manual chambers showed coefficients of variation comprised between 30 and 150 % during the 2 weeks of common observations. This variability may explain the unusual shape of the N 2 O concentration gradient in the atmosphere observed sometimes, which led to the conclusion that the gradient data set contained information allowing the spatial variability in N 2 O emission to be characterized. Hourly micrometeorological fluxes indicated a temporal variability of about 100 % over daily periods. Microbial

This study aims to investigate the ability of high power ultrasound (HPU) to ensure oak barrel sterilization and wood structure preservation. Optimization was performed in terms of temperature and time and the impact of the HPU process on the porous material was also characterized. In this research, several wood characteristics were considered, such as the specific surface area, hydrophobicity, oxygen desorption and spoilage microorganisms after treatment. The study showed that the microbial stabilization could be obtained with HPU 60 °C/6 min. The results obtained show that microorganisms are impacted up to a depth of 9 mm, with a Brettanomyces bruxellensis population < 1 log CFU/g. The operating parameters used during the HPU treatment can also impact on wood exchange surface and oxygen desorption kinetics indicating that tartrate is removed. Indeed, the total oxygen desorption rate was recovered after HPU treatment, close to a new oak barrel, and thus may indicate that there is no impact on the ultrastructure (vessel, pore size or rays). Finally, wood wettability can also be impacted, depending on the temperature and the duration of exposure.

Controlling the Amoco Cadiz spill and cleaning the sea and the coast of Brittany were made highly difficult by rough sea conditions and the location of the grounding. The rapid formation of “chocolate mousse” limited severely the efficiency of the different techniques used. At sea, restrictions on the use of dispersants led to use of both sinking and absorbing agents, including an experimental product, rubber powder. On the coast, several types of chemicals were used or tried; emulsion breakers, sorbents, dispersants, and biodegrading products. Practical examples were given of how some of these products could help the cleanup operations on beaches, rocks, and piers and the handling of oil, polluted sand, and debris. The use of sorbents demonstrated that, despite the additional cost, this approach could be helpful if adequate operational techniques for such use were available.