A laboratory yeast strain suitable for spirit production

Yeast strains of the species Saccharomyces cerevisiae currently in use for the production of consumable alcohols such as beer, wine and spirits are genetically largely undefined. This prevents the use of standard genetic manipulations, such as crossings and tetrad analysis, for strain improvement. Furthermore, it complicates the application of the majority of modern methods developed in yeast molecular biology. Here we used two haploid laboratory strains with suitable auxotrophic markers for the construction of a genetically well defined, prototrophic diploid production strain. This strain was tested for its fermentative and sensory performances in comparison to commercially available yeasts. Three different fruit mashes (cherries, plums and pears) were fermented in a 90 kg scale. These were then subjected to distillation and used for the production of spirits with a final ethanol content of 40% (v/v). Fermentation parameters assayed included growth, sugar utilization, ethanol production and generation of volatile compounds, higher alcohols and glycerol. The spirits were also tested for their sensory performances and the data obtained statistically consolidated. Our results clearly demonstrate that this laboratory strain does not display any disadvantage compared with commercial yeasts in spirit production for any of the parameters tested, yet it offers the potential to apply both classical breeding and modern molecular genetic techniques for adjusting yeast physiology to special production schemes.

Mechanism and role of PDZ domains in signaling complex assembly

PDZ domains are protein-protein recognition modules that play a central role in organizing diverse cell signaling assemblies. These domains specifically recognize short C-terminal peptide motifs, but can also recognize internal sequences that structurally mimic a terminus. PDZ domains can therefore be used in combination to bind an array of target proteins or to oligomerize into branched networks. Several PDZ-domain-containing proteins play an important role in the transport, localization and assembly of supramolecular signaling complexes. Examples of such PDZ-mediated assemblies exist in Drosophila photoreceptor cells and at mammalian synapses. The predominance of PDZ domains in metazoans indicates that this highly specialized scaffolding module probably evolved in response to the increased signaling needs of multicellular organisms.