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.