Disentangling the genetic bases of Saccharomyces cerevisiae nitrogen consumption and adaptation to low nitrogen environments in wine fermentation

The budding yeast Saccharomyces cerevisiae has been considered for more than 20 years as a premier model organ- ism for biological sciences, also being the main microorganism used in wide industrial applications, like alcoholic fermentation in the winemaking process. Grape juice is a challenging environment for S. cerevisiae , with nitrogen deficiencies impairing fermentation rate and yeast biomass production, causing stuck or sluggish fermentations, thus generating sizeable economic losses for wine industry. In the present review, we summarize some recent efforts in the search of causative genes that account for yeast adaptation to low nitrogen environments, specially focused in wine fermentation conditions. We start presenting a brief perspective of yeast nitrogen utilization under wine fermentative conditions, highlighting yeast preference for some nitrogen sources above others. Then, we give an outlook of S. cerevisiae genetic diversity studies, paying special attention to efforts in genome sequencing for population structure determination and presenting QTL mapping as a powerful tool for phenotype-genotype correlations. Finally, we do a recapitulation of S. cerevisiae natural diversity related to low nitrogen adaptation, specially showing how different studies have left in evidence the central role of the TORC1 signalling pathway in nitrogen utilization and positioned wild S. cerevisiae strains as a reservoir of beneficial alleles with potential industrial applications (e.g. improvement of industrial yeasts for wine production). More studies focused in disentangling the genetic bases of S. cerevisiae adaptation in wine fermentation will be key to determine the domestication effects over low nitrogen adaptation, as well as to definitely proof that wild S. cerevisiae strains have potential genetic determinants for better adaptation to low nitrogen conditions.

Profiling carbohydrate composition, biohydrogen capacity, and disease resistance in potato

Background: Potato (Solanum tuberosum) is one of the most important sources of carbohydrates in human diet. Because of its high carbohydrate levels it recently has also received attention in biohydrogen production. To exploit the natural variation of potato with respect to resistance to major diseases, carbohydrate levels and composition, and capacity for biohydrogen production we analyzed tubers of native, improved, and genetically modified potatoes, and two other tuberous species for their glucose, fructose, sucrose, and starch content. Results: High-starch potato varieties were evaluated for their potential for Caldicellulosiruptor saccharolyticus-mediated biohydrogen production with Desirée and Rosita varieties delivering the highest biohydrogen amounts. Native line Vega1 and improved line Yagana were both immune to two isolates (A291, A287) of Phytophthora infestans. Conclusions: Our data demonstrate that native potato varieties might have great potential for further improving the multifaceted use of potato in worldwide food and biohydrogen production.