Trabajo presentado en el 33rd International Specialised Symposium on Yeast (ISSY33), celebrado en Cork (Irlanda), del 26 al 29 de junio de 2017, Sulphur dioxide is used at several stages in winemaking, mainly as antioxidants and as antimicrobial, even before
the onset of fermentation. Sulphites are also used as preservatives in many canned and processed foods. Its
usefulness during wine fermentation depends on the relatively high tolerance to sulphites of wine strains of
Saccharomyces cerevisiae. Sulphite tolerance in wine yeast strains has been related to mutations that boost
transcription of SSU1, the gene coding for a plasma membrane sulphite pump required for efficient sulphite
efflux. We used competition of bar-coded Yeast Knockout (YKO) collections to better understand microbial
sulphite resistance, and sulphite cellular targets. Our results point to some of the cell functions that are more
specifically required to survive sulphite-induced stress. For example, we found increased sulphite sensitivity for
most KO strains involving genes required for autophagy, so pointing to this process as a key one in the
detoxification of sulphite, probably through recycling of damaged proteins. In addition, some deletion strains,
gained some competitiveness in the presence of sulphite (usually strains that were already impaired under
standard growth conditions). These late functions are probably targets of sulphite (i.e. specifically sensitive to
it)., MINECO(AGL2015-63629-R, RTC-2014-2186-2) EU(7FP-IRSES-GA612441); Junta de
Andalucía(P10-AGR6544), Peer reviewed

Trabajo presentado en el 33rd International Specialised Symposium on Yeast (ISSY33), celebrado en Cork (Irlanda), del 26 al 29 de junio de 2017 -- Trabajo presentado al 7th Congress of European Microbiologists (FEMS), celebrado en Valencia (España) del 9 al 13 de julio de 2017, Advances in microbial wine biotechnology have led to the recent commercialization of several non-Saccharomyces starter cultures. These are intended to be used in either simultaneous or sequential inoculation with Saccharomyces cerevisiae. We analysed the transcriptional response to co-cultivation of S. cerevisiae and Torulaspora delbrueckii. The study is focused in the initial stages of wine fermentation with the goal of better understand the microbial interactions that can be stablished during wine fermentation with mixed-starters. Fermentations were carried out in bioreactors using synthetic grape must to mimic industrial conditions. Experiments were carried out in triplicate for fermentation kinetics, CO2 performance and RNAseq analysis.
Both species showed a clear response to the presence of each other, even though the portion of the genome showing altered transcriptional levels was relatively small. Changes in the transcription pattern suggested a stimulation of metabolic activity and growth, as a consequence of the presence of competitors in the same medium. The response of S. cerevisiae seems to take place earlier, as compared to T. delbrueckii. Enhanced glycolytic activity of the mixed culture was confirmed by the CO2 production profile during these early stages of fermentation. Interestingly, HSP12 expression appeared induced by co-cultivation for both of S. cerevisiae and Torulaspora delbrueckii in the two time points studied. This might be related with a recently described role of Hsp12 in intercellular communication in yeast. Expression of S. cerevisiae PAU genes was also stimulated in mixed cultures., MINECO (AGL2015-63629-R,RTC-2014-2186-2); EU (7FP-IRSES-GA612441); (JdC- JA.Curiel)., Peer reviewed

Trabajo presentado en el 33rd International Specialised Symposium on Yeast (ISSY33), celebrado en Cork (Irlanda), del 26 al 29 de junio de 2017, Our group is interested in reducing ethanol yield during wine fermentation, to counter the growing sugar content in grapes due to climate change, and avoid the negative impact of increasing ethanol content in the wine market. While respiratory metabolism appears as an attractive alternative to pure fermentation, to redirect carbon flux towards sensory neutral products (CO2), both the Crabtree effect of Saccharomyces cerevisiae and the tendency to increased acetic acid production during aeration (as we have previously shown), constitute a hurdle to industrial application of respiration compatible fermentation conditions. However, mechanisms involved in acetic acid production by S. cerevisiae in the presence of oxygen are yet poorly understood. We addressed this topic by deletion of several genes, HXK2, REG1, PDE2, PDC1 (homozygous) and PYK1 (heterozygous) in the wine yeast strain FX0 (Laffort) background. Some of them had been previously related with the Crabtree effect. Our results show that oxygenation helps reducing ethanol content of wines. However, there is little impact of the deletions on this reduction. Interestingly, some of these deletions do results in a reduction in acetate yields during oxygenated fermentation of natural grape must., MINECO(AGL2015-63629-R, RTC-2014-2186-2) EU(7FP-IRSES-GA612441); Junta de Andalucía(P10-AGR6544), Peer reviewed

Trabajo presentado al 7th Congress of European Microbiologists (FEMS), celebrado en Valencia (España) del 9 al 13 de julio de 2017, Sulphur dioxide (often dosed as bisulphite salts) has had widespread use in winemaking for centuries. It is used at several stages of the process, and for several purposes, mainly as antioxidants and as antimicrobials, even before the onset of fermentation. Sulphites are also used as preservatives in many canned and processed foods. Its usefulness during wine fermentation depends on the relatively high tolerance to sulphites of industrial wine strains of the yeast Saccharomyces cerevisiae. Sulphite tolerance of these yeast strains is related to mutations that promote high level transcription of SSU1, the gene coding for a plasma membrane sulphite pump required for efficient sulphite efflux.

This work was designed, in order to better understand sulphite cellular targets in yeast, as well as microbial sulphite resistance.

By competition of bar-coded Yeast Knockout (YKO) collections we have identified some of the cell functions that are more specifically required in order to survive sulphite insult.

Our results show increased sulphite sensitivity for most KO strains involving genes required for autophagy, so pointing to this process as a key one in the detoxification of sulphite, probably through recycling of damaged proteins. Conversely, some deletion yeast strains, that were impaired under no-stressed conditions, recovered some competitiveness in the presence of sulphite. These functions are probably specifically sensitive to sulphite, so that already defective strains do not suffer from an additional impairment in the presence of sulphite., MINECO(AGL2015-63629-R, RTC-2014-2186-2) EU(7FP-IRSES-GA612441); Junta de Andalucía(P10-AGR6544), Peer reviewed