Investigation of the bactericidal effect of Nisin on lactic acid bacteria of wine

Untersuchung der bakteriziden Wirkung von Nisin auf Milchsäurebakterien des WeinesGeringe Konzentrationen des Polypeptids Nisin genügen, um das Wachstum der für Wein wichtigen Milchsäurebakterien zu hemmen. Die Hemmkonzentrationen sind sehr verschieden: Leuconostoc oenos, Pediococcus damnosus und Lactobacillus brevis werden bei 4, 8 und 100 IU Nisin/ml gehemmt. Unterhalb der Hemmkonzentration wird der Carboxylsäurestoffwechsel nicht beeinflußt. Nisin ist für nicht wachsende Milchsäurebakterien bakterizid, aber erst bei wesentlich höheren als den wachstumshemmenden Konzentrationen. Lactobacillus casei erwies sich als extrem resistent und wurde erst bei Konzentrationen von > 2000 IU Nisin/ml abgetötet

Expression profile of genes involved in hydrogen sulphide liberation by _Saccharomyces cerevisiae_ grown under different nitrogen concentrations

The present work aims to elucidate molecular mechanisms underlying hydrogen sulphide production in _S. cerevisiae_ associated to nitrogen deficiency. To assess, at a genome-wide level, how the yeast strain adapted to the progressive nitrogen depletion and to nitrogen re-feeding, gene expression profiles were evaluated during fermentation at different nitrogen concentrations, using the DNA array technology. The results showed that most MET genes displayed higher expression values at the beginning of both control and N-limiting fermentation, just before the time at which the release of sulphide was observed. MET genes were downregulated when yeast stopped growing which could associate MET gene expression levels with cell growth. The over expression of MET genes after nitrogen addition was confirmed by a new release of H2S during the new set of fermentation experiments. In addition, to confirm gene expression profiles observed from macroarray results, real time RT-PCR was performed on 6 genes using additional sets of biological replicates. These genes were selected based on the assumption that differences in sulphide production observed among strains are due to genetic variations of the expression of genes involved in the Sulphate Reduction Pathway. An integration of expression data of genes involved in sulphur assimilation and sulphur amino acid biosynthesis with hydrogen sulphide production is presented

Uso de Pediococcus parvulus para a degradação e destoxificação biológica de ocratoxina A, respetivo método e kit

National Patent (INPI)A presente invenção refere-se ao uso de um microrganismo para a degradação e destoxificação biológica de micotoxinas, mais especificamente para a degradação da ocratoxina A em ocratoxina a. Concretamente, relaciona-se com o uso de Pediococcus parvulus para a destoxificação de alimentos e rações. Outro aspeto da presente invenção relaciona-se com o método de destoxificação e a sua aplicação a um kit. A invenção insere-se na área farmacêutica, alimentar e veterinária.info:eu-repo/semantics/publishedVersio

Efeito do etanol no crescimento de bactérias lácticas

Neste trabalho foi estudado o efeito do etanol no crescimento-taxa de crescimento, duração da fase lag e produção de biomassa total (medida em absorvância a 600 nm)- de espécies do género Leuconostoc, Pediococcus e Lactobacillus, isoladas de vinhos. This study deals with the effect of ethanol on the growth rate, lag phase and biomass production by several strains classified under the genera Leuconostoc. Pediococcus and Lactobaciflus. Low concentrations of ethanol significantly increased the growth rate of all strains, which intensity was variable with the pH and among the strains. The repressive effect of ethanol, at higher concentrations, on the bacterial growth was more relevant in Leuconostoc than with Lactobaciflus and Pediococcus. Besides, this effect was significantly dependent of the initial pH of the culture medium

Effect of different fining agents and additives in white wine protein stability

Proteins in white wine could become insoluble and precipitate causing the appearance of a haze in bottled wine. Protein instability may be due to intrinsically or extrinsically factor such as protein molecular weight, isoelectric point, ionic strength, alcohol degree and wine pH or storage temperature. These modifications may occur during aging, storage or when diverse wines are blended. The type and concentration of proteins in the wine depends on grape variety, maturation degree and winemaking operations (pre-fem1entative grape maceration, application of tannins, enzymes or bentonite fining). Usually, the treatment for wine protein instability is sodium bentonite fining. The adsorption of wine proteins onto bentonite is due to the cationic exchange capacity of bentonite, which carries a net negative charge and the wine proteins are mostly positive charged at wine pH, and thus can be exchanged onto bentonite. Sometimes even with high level of sodium bentonite wines do not stabilize. Thus, the main purpose of this work is to understand the interaction of different types of bentonites, tannins, carboxylmethylcellulose (CMC) and mannoproteins on white wine protein stability, to get new approaches to stabilize them. Some trials were performed in four white wines with high protein instability. Preliminary results showed that sodium bentonite and mannoproteins increase protein stability, in opposition, CMC and tannins seems to increase turbidity after stability tests, which means more instability. Final results could provide important information to the wine industry to select alternative treatments to remove unstable proteins to maintain or improve wine quality

Characterizing the potential of the non-conventional yeast Saccharomycodes ludwigii UTAD17 in winemaking

Non-Saccharomyces yeasts have received increased attention by researchers and winemakers, due to their particular contributions to the characteristics of wine. In this group, Saccharomycodes ludwigii is one of the less studied species. In the present study, a native S. ludwigii strain, UTAD17 isolated from the Douro wine region was characterized for relevant oenological traits. The genome of UTAD17 was recently sequenced. Its potential use in winemaking was further evaluated by conducting grape-juice fermentations, either in single or in mixed-cultures, with Saccharomyces cerevisiae, following two inoculation strategies (simultaneous and sequential). In a pure culture, S. ludwigii UTAD17 was able to ferment all sugars in a reasonable time without impairing the wine quality, producing low levels of acetic acid and ethyl acetate. The overall effects of S. ludwigii UTAD17 in a mixed-culture fermentation were highly dependent on the inoculation strategy which dictated the dominance of each yeast strain. Wines whose fermentation was governed by S. ludwigii UTAD17 presented low levels of secondary aroma compounds and were chemically distinct from those fermented by S. cerevisiae. Based on these results, a future use of this non-Saccharomyces yeast either in monoculture fermentations or as a co-starter culture with S. cerevisiae for the production of wines with greater expression of the grape varietal character and with flavor diversity could be foreseen. View Full-Textinfo:eu-repo/semantics/publishedVersio

Volatile composition and sensory properties of mead

Mead is a traditional beverage that results from the alcoholic fermentation of diluted honey performed by yeasts. Although the process of mead production has been optimized in recent years, studies focused on its sensory properties are still scarce. Therefore, the aim of this work was to analyse the sensory ttributes of mead produced with free or immobilized cells of the Saccharomyces cerevisiae strains QA23 and ICV D47, and to establish potential correlations with its olatile composition. In the volatile composition of mead, the effect of yeast condition was more important than the strain. In respect to sensory analysis, the most pleasant aroma descriptors were correlated with mead obtained with free yeast cells, independently of the strain. Both sensory analysis and volatile composition indicates that the most pleasant mead was produced by free yeast cells. Although this study has provided a significant contribution, further research on the sensory quality of mead is still needed.Portuguese Foundation for Science and Technology (FCT) through a PhD grant (SFRH/BD/45820/2008). This research was partially supported through the PTDC project (PTDC/AGR-ALI/68284/2006) awarded by the FCT. This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by European Regional Development Fund under the scope of Norte2020 – Programa Operacional Regional do Norteinfo:eu-repo/semantics/publishedVersio

Mead production: selection and characterization assays of Saccharomyces cerevisiae

Mead is a traditional alcoholic drink which results from the fermentation of diluted honey. Yeasts used in mead production are, usually, wine Saccharomyces cerevisiae strains. Most of these yeasts are not adapted to the conditions of mead production namely, high sugar levels, low pH values and reduced nitrogen concentrations. The inability of yeast strains to respond and adapt to unfavorable stressful growth conditions, leads to several problems, such as lack of uniformity of the final product, delays and “pouts” fermentations, as well as the production of off-flavors by the yeasts. Therefore, it is necessary to find yeast strains more suitable for mead production

Biodegradation of ochratoxin A by Pediococcus parvulus isolated from Douro wines

Lactic acid bacteria (LAB) are a promising solution to reduce exposure to dietary mycotoxins because of the unique mycotoxin decontaminating characteristic of some LAB. Ochratoxin A (OTA) is one of the most prominent mycotoxins found in agricultural commodities. The present work reports on the ability of Pediococcus parvulus strains that were isolated from Douro wines that spontaneously underwent malolactic fermentation to detoxify OTA. These strains were identified and characterised using a polyphasic approach that employed both phenotypic and genotypic methods. When cultivated on OTA-supplemented MRS media, OTA was biodegraded into OTα by certain P. parvulus strains. The presence of OTα was confirmed using LC-MS/MS. The conversion of OTA into OTα indicates that the OTA amide bond was hydrolysed by a putative peptidase. The rate of OTA biodegradation was found to be dependent on the inoculum size and on the incubation temperature. Adsorption assays with dead P. parvulus cells showed that approximately 1.3% ± 1.0 of the OTA was adsorbed onto cells wall, which excludes this mechanism in the elimination of OTA by strains that degrades OTA. Under optimum conditions, 50% and 90% of OTA was degraded in 6 and 19 h, respectively. Other LAB strains that belonged to different species were tested but did not degrade OTA. OTA biodegradation by P. parvulus UTAD 473 was observed in grape must. Because some P. parvulus strains have relevant probiotic properties, the strains that were identified could be particularly relevant to food and feed applications to counteract the toxic effects of OTA.This work was funded by FEDER funds through the "Programa Operacional Factores de Competitividade - COMPETE" and by national funds through "Fundacao para a Ciencia e a Tecnologia - FCT", Ref. FCOMP-01-0124-FEDER-028029 and PTDC/AGR-TEC/3900/2012, respectively. The authors also thank the FCT Strategic Project PEst-OE/EQB/LA0023/2013 and the Project "BioInd - Biotechnology and Bioengineering for improved Industrial and Agro-Food processes, REF. NORTE-07-0124-FEDER-000028" co-funded by the Programa Operacional Regional do Norte (ON.2 - O Novo Norte), QREN, FEDER. Luis Abrunhosa was supported by the grant SFRH/BPD/43922/2008 from FCT

The Role of Yeasts and Lactic Acid Bacteria on the Metabolism of Organic Acids during Winemaking

The main role of acidity and pH is to confer microbial stability to wines. No less relevant, they also preserve the color and sensory properties of wines. Tartaric and malic acids are generally the most prominent acids in wines, while others such as succinic, citric, lactic, and pyruvic can exist in minor concentrations. Multiple reactions occur during winemaking and processing, resulting in changes in the concentration of these acids in wines. Two major groups of microorganisms are involved in such modifications: the wine yeasts, particularly strains of Saccharomyces cerevisiae, which carry out alcoholic fermentation; and lactic acid bacteria, which commonly conduct malolactic fermentation. This review examines various such modifications that occur in the pre-existing acids of grape berries and in others that result from this microbial activity as a means to elucidate the link between microbial diversity and wine composition