The speed-controlling reactions in fermentation of quickly dried yeast

Several factors which influence the speed of fermentation of quickly dried yeast are investigated. If the yeast is washed and the bulk of coenzymes and phosphate is removed, addition of 0.5 μmole diphosphopyridine nucleotide (DPN) and 0.5 μmole adenosine triphosphate (ATP) per cc. is necessary for maximal speed. In the optimal pH range, which lies between 6.6 and 6.2, and with optimal amounts of cofactors, there is no influence of nicotinamide mononucleotide (NMN), but with suboptimal amounts of DPN, the speed is raised by synthesis to DPN.The dialyzate of boiled juice contains factors which raise the speed of washed yeast by 20–30% of the maximum obtained in the presence of the usual cofactors. A phosphate concentration of 0.01–0.02 M is likewise necessary even if the phosphate is only partly esterified. At pH 6.0 to 5.9 the speed is less than half that at pH 6.5.Fermentation is completely absent without either K⁺ or NH₄⁺ and without Mg. The optimal amount of the monovalent ions is 5 × 10^?2M. Sodium alone is unable to allow fermentation but is only slightly harmful if enough K⁺ or NH₄⁺ is present.Addition of small amounts of phosphoglycerate at optimal potassium phosphate concentration and pH increases the rate of sugar fermentation and gives rise to an extra CO₂ formation during the time of phosphoglycerate decomposition of about 3 to 5 times the amount added.     

Appearance and establishment of diazotrophic cyanobacteria in Lake Kinneret,Israel

1. We propose that the appearance and establishment of Nostocales (cyanobacteria) species of the genera Aphanizomenon and Cylindrospermopsis in the warm subtropical Lake Kinneret (Sea of Galilee, Israel) from 1994 was linked to changes in climate conditions and summer nitrogen (N) availability. 2. From 1994 to 2009, an increase in frequency of events of elevated water temperature (>29 °C) in summer, and to some extent a greater frequency of lower summer wind speed events, affected water turbulence and water column stratification, thus providing better physical conditions for the establishment of these populations. 3. In recent years, N‐depleted conditions in Lake Kinneret in early summer have promoted the development and domination of Nostocales that could gain an ecological advantage owing to their N₂‐fixing capability. 4. Nitrogen fixation rates coincided both with heterocyst abundance and with Nostocales biomass. The N supplied to the lake via nitrogen fixation ranged from negligible quantities when Nostocales represented only a minor component of the phytoplankton community to 123 tonnes when Cylindrospermopsis bloomed in 2005. This high N₂ fixation rate equals the average summer dissolved inorganic nitrogen load to the lake via the Jordan River.