New article on the effect of melatonin in transcriptomics of S. cerevisiae

Transcriptomic insight into the effect of melatonin in Saccharomyces cerevisiae in the presence and absence of oxidative stress

Mercè Sunyer-Figueres, Jenny Vázquez, Albert Mas, M. Jesús Torija, Gemma Beltran

Antioxidants 2020, 9, 947.  https://www.mdpi.com/2076-3921/9/10/947

  Melatonin plays important roles in biological processes in humans, so its study has growing interest. Saccharomyces cerevisiae produces melatonin during alcoholic fermentation, and recent studies report that it has an antioxidant role in yeast cells, not only directly neutralizing the effects of oxidative stress, also modulating the expression of genes involved in antioxidant response.

  In order to study the effects of melatonin in the global gene response of yeast, we determined the transcriptomic state of cells that were supplemented with melatonin and exposed or non-exposed to oxidative stress.

  We found that melatonin crossed cellular membranes and regulated the transcription of several genes, related to transport, signaling, antioxidant activity or several metabolisms. The most regulated genes by melatonin were the mitochondrial ones (mainly those related to electron transport chain), and its expression was downregulated in absence of oxidative stress and upregulated in its presence. Therefore, we concluded that melatonin can reprogram different cellular processes to achieve tolerance to oxidative stress.

New article on the favourable impact of Torulaspora delbrueckii on malolactic fermentation

Impact of changes in wine composition produced by non-Saccharomyces on malolactic fermentation

Aitor Balmaseda, Nicolas Rozès, Miguel Ángel Leal, Albert Bordons, Cristina Reguant

International Journal of Food Microbiology 2021, 337, 108954. https://doi.org/10.1016/j.ijfoodmicro.2020.108954

    Nowadays, non-Saccharomyces yeasts have increasing interest in winemaking. This is particularly true of Torulaspora delbrueckii and Metschnikowia pulcherrima, which are inoculated before S. cerevisiae, in so called sequential inoculation. As result of the different yeast combination, wine chemical characteristics are modulated. 

    In this sense, not only aromatic and colour parameters are influenced, but also those compounds related to the performance of the subsequent malolactic fermentation. Oenococcus oeni is the main species which carries out this fermentative process, will be positively, neutrally or negatively affected by the result of the fermenting yeast's metabolisms. Indeed, novel researches in this field postulate some non-Saccharomyces as good culture starter combination together with O. oeni for developing malolactic fermentation. 

    This paper aims to study the effects of those two non-Saccharomyces yeasts on malolactic fermentation carried out by two strains of O. oeni and also a spontaneous fermentation, under cellar conditions. Studying both, white and red winemaking processes. In general, non-Saccharomyces created more MLF friendly conditions, largely because of lower concentrations of SO2 and medium chain fatty acids. The most favourable results were observed in wines inoculated with T. delbrueckii, that seemed to promote the development of O. oeni and improve MLF performance. 

New article on the effect of non-Saccharomyces on malolactic fermentation and Oenococcus oeni

Evaluating the effect of using non-Saccharomyces on Oenococcus oeni and wine malolactic fermentation

Núria Ferrando, Isabel Araque, Alba Ortís, Gabriel Thornes, Joaquín Bautista-Gallego, Albert Bordons, Cristina Reguant

Food Research International 2020, 138 B, 109779 https://doi.org/10.1016/j.foodres.2020.109779

    Interest in using non Saccharomyces yeasts in winemaking has increased recently due to their ability to improve organoleptic characteristics. Since there is little information on their effects on malolactic fermentation (MLF) and Oenococcus oeni, we studied it with different strains of Torulaspora delbrueckii, Metschnikowia pulcherrima, Hanseniaspora uvarum, H. vineae and Starmerella bacillaris (syn. Candida zemplinina). We used them in sequential alcoholic fermentation with S. cerevisiae, followed by inoculation with four O. oeni strains. 

    The main results were that some of O. oeni strains could not perform MLF in H. uvarum wine and in some cases, MLF was inhibited in S. bacillaris wines. Also, all the H. uvarum and H. vineae strains increased notably acetic acid and some of them increased SO₂. On the contrary, the best conditions for MLF were provided by some T. delbruecckii and M. pulcherrima strains, with increased concentrations of mannoproteins, no production of SO₂, and low consumption of L-malic acid. In conclusion, these species T. d. and M. p. showed the best compatibility with MLF development.

 

Call for abstracts ENOFORUM WEB CONTEST 2021

A global virtual competition to showcase innovative research to the wine industry. 

The winning research work will bring 10.000€ to the main author research. 

Award evaluation procedure coupled with the program of Enoforum Web Conference (23-25 Feb 2021). 

Authors who wish to candidate to Enoforum Web Contest 2021 by presenting one or more research papers performed in the last three years, must complete the following online form by November 6th, 2020, including an abstract of the research (in English and in original language), max 1800 characters. 

More info: Enoforum Web Contest 2021 call for abstract

and https://www.enoforum.eu/en/enoforum-web-conference-2021/

New article on monitoring yeast population by viability-PCR in mixed fermentations

Viability-PCR allows monitoring yeast population dynamics in mixed fermentations including viable but non-culturable yeasts

Yurena Navarro, M. Jesús Torija, Albert Mas, Gemma Beltran

Foods 2020, 9, 1373 : https://www.mdpi.com/2304-8158/9/10/1373

    The use of mixed controlled inocula of Saccharomyces cerevisiae and non-Saccharomyces yeasts is becoming a common practice in winemaking. The control of the process requires better knowledge of yeast growth and interactions. Although S. cerevisiae is usually the dominant yeast at the end of mixed fermentations, some non-Saccharomyces species can also reach the later stages. 

    Some of these species may not grow in traditional culture media, which is a status known as Viable but not cultivable (VBNC). The presence of this VBNC status produces an underestimation of the final population. To avoid this problem, quantitative PCR (qPCR) has been found to be a good and sensitive method to determine the identity of the cell population. The main problem is that the amplification of DNA can also include dead cells. 

    Thus, viability dyes (such as PMAxx) have been proposed to avoid the amplification and, therefore, the quantification of DNA from non-viable cells. In this study we demonstrated that PMAxx coupled with qPCR is a reliable, specific and rapid method to accurately quantify the viable yeast species most commonly used. 

    We have used 4 different species (S. cerevisiae, T. delbrueckii, L. thermotolerans and M. pulcherrima) in mixed wine fermentations, to compare PMAxx-PCR to non-dyed qPCR and colony counting on differential medium. We have observed, for the first time, the entry into the VBNC status in L. thermotolerans and S. cerevisiae during alcoholic fermentation. 

New position offer for Doctoral Grant in our group

Research subject: "Establishment of microbial consortia for the improvement of wine quality and stability"

Application is open until 27th October 2020.

Info contact: M. Jesús Torija (mjesus.torija@urv.cat)

More details and application of this grant (Spanish Ministry of Science): click here.

New article on comparison of methods in wine metabolomics

Qualitative factor-based comparison of NMR, targeted and untargeted GC-MS and LC-MS on the metabolomic profiles of Rioja and Priorat red wines. 

Dimitrios Kioroglou, Albert Mas, M. Carmen Portillo

Foods 9, 1381 : https://www.mdpi.com/2304-8158/9/10/1381

    Wine origin and ageing are two factors related to wine quality which in turn is associated to wine metabolome. Currently, new metabolomic techniques and proper statistics procedures allow accurate profiling of wine metabolome. 

    In the current study, we implement NMR, targeted and untargeted GC-MS and LC-MS metabolomic analytical techniques so as to gain insights into the volatile and nonvolatile wine metabolome composition of red wines from two cellars located in the only two Spanish Qualified Appellations of Origin:DOQ Priorat and DOCa Rioja regions. 

    The results suggest that a combination of different metabolomic techniques is necessary for a complete overview of the metabolome changes and ease the selection of the correct methodology depending on the specific factor investigated.