Growth and fermentation patterns of Saccharomyces cerevisiae under different ammonium concentrations and its implications in winemaking industry

To study the effects of assimilable nitrogen concentration on growth profile and on fermentation kinetics of Saccharomyces cerevisiae. Aims: To study the effects of assimilable nitrogen concentration on growth profile and on fermentation kinetics of Saccharomyces cerevisiae. Methods and Results: Saccharomyces cerevisiae was grown in batch in a defined medium with glucose (200 g l−1) as the only carbon and energy source, and nitrogen supplied as ammonium sulphate or phosphate forms under different concentrations. The initial nitrogen concentration in the media had no effect on specific growth rates of the yeast strain PYCC 4072. However, fermentation rate and the time required for completion of the alcoholic fermentation were strongly dependent on nitrogen availability. At the stationary phase, the addition of ammonium was effective in increasing cell population, fermentation rate and ethanol. Conclusions: The yeast strain required a minimum of 267 mg N l−1 to attain complete dryness of media, within the time considered for the experiments. Lower levels were enough to support growth, although leading to sluggish or stuck fermentation. Significance and Impact of the Study: The findings reported here contribute to elucidate the role of nitrogen on growth and fermentation performance of wine yeast. This information might be useful to the wine industry where excessive addition of nitrogen to prevent sluggish or stuck fermentation might have a negative impact on wine stability and quality

Multi-messenger Observations of a Binary Neutron Star Merger

International audienceOn 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim 1.7\,{\rm{s}}$ with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg(2) at a luminosity distance of ${40}_{-8}^{+8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 $\,{M}_{\odot }$. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim 40\,{\rm{Mpc}}$) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ∼10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position $\sim 9$ and $\sim 16$ days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC 4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta