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

The influence of supplementary light on Dorper lambs fed intensively

The objective of this trial was to quantify the differences in average daily gain (ADG), backfat thickness (BFT), eye muscle area (EMA), fat thickness (FT) on different body parts, the feed conversion ratio (FCR), body measurements and the weight of internal organs of Dorper lambs exposed to supplemented light. For this study 120 Dorper lambs (115 ± 10 days old), weighing 29.8 ± 5.01 kg, were used. The lambs were randomly divided into three homogeneous groups (20 castrated and 20 intact males/group). Two groups were then exposed to either 16 h or 24 h of supplemented light at 145 lux, and a control the normal photoperiod. The animals were fedad libitum with pellets containing 9.5 MJ ME/kg DM and 120 g CP/kg in open pens. The animals were weighed every seven days while ultrasound scanning of the EMA and BFT was done at the beginning and the end of the 35 d trial. The ADG, FCR and feed intake (FI) were calculated at the end of the trial. Linear body measurements including shoulder height, body length and heart girth were taken at days 1 and 35. All the animals were slaughtered at the end of the trial. The carcasses were weighed, graded and the FT was measured with a caliper. It was concluded that there are no differences between treatments in terms of body measurements, ultrasound scanning, ADG and FCR

Differential utilisation of sulfur compounds for H(2)S liberation by nitrogen-starved wine yeasts

Hydrogen sulfide (H2S) liberation by Saccharomyces cerevisiae wine yeast was studied as a function of different inorganic sulfurous precursors using a model winemaking system. In a medium analogous to grape juice, and following nitrogen starvation of the yeast culture, a combination of 5 mM sulfate and 300 μM sulfite was more potent than 5 mM sulfate alone as a substrate for H2S liberation. Sulfate plus sulfite allowed H2S liberation in greater amounts, at higher rates and over a longer period than sulfate alone, by most of the five yeast strains examined. Nevertheless, a sulfate-only medium still supported the liberation of between 11 and 86% of the H2S observed in the sulfate plus sulfite medium. After nitrogen depletion of the medium, sulfate uptake by yeast cells was stable for at least 7 h and even increased in a cycloheximide-sensitive manner by ca 35%. The relatively limited formation of H2S from sulfate is therefore not attributable to losses of sulfate transport by the culture as might occur through elevated permease turnover. Similarly, an inhibition of sulfate transport could not account for the lesser formation of H2S from sulfate because cultures starved of nitrogen in the presence of sulfate continued to accumulate sulfate in excess of the rates of H2S liberation. Instead, sulfate deprivation/supplementation experiments implied that limited utilisation of sulfate was due to an inhibition of sulfate reduction to sulfide. Experiments also highlighted a contribution by intracellular sulfur pools of between 35 and 70% to the total H2S liberated from sulfate by nitrogen starved yeasts. As a component of this pool, glutathione was a precursor for 40% of the H2S liberated from sulfate-containing medium.Hallinan, Christopher P. ; Saul, David J. ; Jiranek, Vladimi

The 3rd DBCLS BioHackathon: improving life science data integration with Semantic Web technologies

Background: BioHackathon 2010 was the third in a series of meetings hosted by the Database Center for Life Sciences (DBCLS) in Tokyo, Japan. The overall goal of the BioHackathon series is to improve the quality and accessibility of life science research data on the Web by bringing together representatives from public databases, analytical tool providers, and cyber-infrastructure researchers to jointly tackle important challenges in the area of in silico biological research. Results: The theme of BioHackathon 2010 was the 'Semantic Web', and all attendees gathered with the shared goal of producing Semantic Web data from their respective resources, and/or consuming or interacting those data using their tools and interfaces. We discussed on topics including guidelines for designing semantic data and interoperability of resources. We consequently developed tools and clients for analysis and visualization. Conclusion: We provide a meeting report from BioHackathon 2010, in which we describe the discussions, decisions, and breakthroughs made as we moved towards compliance with Semantic Web technologies - from source provider, through middleware, to the end-consumer. source provider, through middleware, to the end-consumer