RESUMEN
Background Saccharomyces cerevisiae is the main microorganism responsible for alcoholic fermentation. In this process, the consumption of nitrogen is of great importance since it is found in limiting quantities and its deficiency produces sluggish and/or stuck fermentations generating large economic losses in the wine-making industry. In a previous work we compared the transcriptional profiles between genetically related strains with differences in nitrogen consumption, detecting genes with differential expression that could be associated to the differences in the levels of nitrogen consumed. One of the genes identified was ICY1. With the aim of confirming this observation, in the present work we evaluated the consumption of ammonium during the fermentation of strains that have deleted or overexpressed this gene. Results Our results confirm the effect of ICY1 on nitrogen uptake by evaluating its expression in wine yeasts during the first stages of fermentation under low (MS60) and normal (MS300) assimilable nitrogen. Our results show that the mRNA levels of ICY1 diminish when the amount of assimilable nitrogen is low. Furthermore, we constructed strains derived from the industrial strain EC1118 as a null mutant in this gene as well as one that overexpressed it. Conclusions Our results suggest that the expression of ICY1 is regulated by the amount of nitrogen available in the must and it is involved in the consumption of ammonium, given the increase in the consumption of this nitrogen source observed in the null mutant strain.
Asunto(s)
Saccharomyces cerevisiae/genética , Vino/microbiología , Levaduras/genética , Fermentación , Saccharomyces cerevisiae/metabolismo , Levaduras/metabolismo , Expresión Génica , Clonación Molecular , Eliminación de Gen , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa/métodos , NitrógenoRESUMEN
The stability and physiological activity of the wine yeast during long-term tank to tank culture, customary enological practice, were studied under the production conditions. The results indicted that, during about one month of tank to tank culture, the yeast cells could remain the fermentative activity and the fine characters selected of the initiative yeast. On the other hand, it was also observed that, yeast cells'alcoholic fermentation of tank to tank culture might be more active than that of the initiative yeast, perhaps due to the selection by grape musts.