20 research outputs found
Susceptibility of wine spoilage yeasts and bacteria in the planktonic state and biofilms as disinfectants
The aim of this work was to determine the ability
of six yeast and two bacterial species associated with wine
spoilage to form biofilms in mono- or co-culture using the
Calgary Biofilm Device (CBD). Moreover, the efficacy of
several disinfectants was evaluated against these spoilage
microorganisms, both in the planktonic and the biofilm
states. Results showed that Dekkera bruxellensis, Saccharomyces
cerevisiae, Saccharomycodes ludwigii, Schizosaccharomyces
pombe and Acetobacter aceti formed biofilms
both in wine and in synthetic medium. Zygosaccharomyces
bailii formed biofilm only in wine and Pichia guilliermondii
and Lactobacillus hilgardii formed biofilms only in
synthetic medium. In wine, D. bruxellensis presented the
same biofilm population when grown in pure culture or in
mixed culture with acetic acid bacteria. There was a 3-log
increase in biofilm formed by A. aceti in mixed culture with
L. hilgardii. Alkaline chlorine-based disinfectant was the
most effective in decontaminating spoilage yeast and
bacteria both in planktonic and biofilm tests. Sodium
hydroxide-based detergents and peracetic-based disinfectant
were also efficient against suspended cells, but at least 10-
fold more concentrated solutions were needed to remove
the biofilms. Furthermore, the results showed that, except
for the neutral detergent VK10, the tested agents wereactually effective when used under the conditions recommended
by manufacturers. In any case, biofilms showed
greater tolerance to biocides when compared to the same
microorganisms in the planktonic state. To our knowledge,
this is the first study in which the CBD is used to assess the
ability of wine spoilage microorganisms to form biofilms
and their susceptibilities to disinfectant agent
Autochthonous fermentation starters for the industrial production of Negroamaro wines
Abstract
The aim of the present study was to establish a new procedure for the oenological selection of Saccharomyces cerevisiae strains isolated from natural must fermentations of an important Italian grape cultivar, denoted as "Negroamaro". For this purpose, 108 S. cerevisiae strains were selected as they did not produce H2S and then assayed by microfermentation tests. The adopted procedure made it possible to identify 10 strains that were low producers of acetic acid and hydrogen sulphide and showed that they completed sugar consumption during fermentation. These strains were characterized for their specific oenological and technological properties and, two of them, strains 6993 and 6920, are good candidates as industrial starter cultures. A novel protocol was set up for their biomass production and they were employed for industrial-scale fermentation in two industrial cellars. The two strains successfully dominated the fermentation process and contributed to increasing the wines' organoleptic quality. The proposed procedure could be very effective for selecting "company-specific" yeast strains, ideal for the production of typical regional wines. "Winery" starter cultures could be produced on request in a small plant just before or during the vintage season and distributed as a fresh liquid concentrate culture
New insights into the oenological significance of Candida zemplinina. Impact of selected autochthonous strains on the volatile profile of Apulian wines
In this investigation, we explored the oenological significance of Candida zemplinina (syn. Starmerella bacillaris) isolates from Apulian grape musts. Moreover, we provide the first evidence of the impact of different C. zemplinina strains on the wine aromatic properties tested as monocultures. We described the diversity of C. zemplinina strains isolated from grapes and the variability of âvolatileâ phenotypes associated with this intraspecific variability. Thirty-three isolates were characterized at strain level by PCR-based approach and, among these, 16 strains were identified and then tested by microfermentation tests carried out in grape must. Analyzed strains were low producers of acetic acid and hydrogen sulphide, not able to decarboxylate a panel of representative amino acids, whereas they showed fructophilic character and significant glycerol production. Volatile profiles of produced wines were investigated by gas chromatographyâmass spectrometry. The Odor Activity Values of all molecules were calculated and 12 compounds showed values above their odor thresholds. Two selected strains (35NC1 and 15PR1) could be considered as possible starter cultures since they were able to positively affect the sensory properties of obtained wine. This report firstly supplies evidence on the strain-specific impact of different C. zemplinina strains on the final aroma of produced wines
Molecular and Technological Characterization of Saccharomyces cerevisiae
The characterization of autochthonous Saccharomyces cerevisiae strains is an important step towards the conservation and employment of microbial biodiversity. The utilization of selected autochthonous yeast strains would be a powerful tool to enhance the organoleptic and sensory properties of typical regional wines. In fact, indigenous yeasts are better tailored to a particular must and because of this they are able to praise the peculiarities of the derived wine. The present study described the biodiversity of indigenous S. cerevisiae strains isolated from natural must fermentations of an ancient and recently rediscovered Apulian grape cultivar, denoted as âSusumaniello.â The yeast strains denoted by the best oenological and technological features were identified and their fermentative performances were tested by either laboratory assay. Five yeast strains showed that they could be excellent candidates for the production of industrial starter cultures, since they dominated the fermentation process and produced wines characterized by peculiar oenological and organoleptic features
From grape berries to wine: population dynamics of cultivable yeasts associated to âNero di Troiaâ autochthonous grape cultivar
The aim of this work was to study the biodiversity of yeasts isolated from the autochthonous grape variety called âUva di Troiaâ, monitoring the natural diversity from the grape berries to wine during a vintage. Grapes were collected in vineyards from two different geographical areas and spontaneous alcoholic fermentations (AFs) were performed. Different restriction profiles of ITSâ5.8S rDNA region, corresponding to Saccharomyces cerevisiae, Issatchenkia orientalis, Metschnikowia pulcherrima, Hanseniaspora uvarum, Candida zemplinina, Issatchenkia terricola, Kluyveromyces thermotolerans, Torulaspora delbrueckii, Metschnikowia chrysoperlae, Pichia fermentans, Hanseniaspora opuntiae and Hanseniaspora guilliermondii, were observed. The yeast occurrences varied significantly from both grape berries and grape juices, depending on the sampling location. Furthermore, samples collected at the end of AF revealed the great predominance of Saccharomyces cerevisiae, with a high intraspecific biodiversity. This is the first report on the population dynamics of âcultivableâ microbiota diversity of âUva di Troiaâ cultivar from the grape to the corresponding wine (âNero di Troiaâ), and more general for Southern Italian oenological productions, allowing us to provide the basis for an improved management of wine yeasts (with both non-Saccharomyces and Saccharomyces) for the production of typical wines with desired unique traits. A certain geographical-dependent variability has been reported, suggesting the need of local based formulation for autochthonous starter cultures, especially in the proportion of the different species/strains in the design of mixed microbial preparations
Biodiversity and safety aspects of yeast strains characterized from vineyards and spontaneous fermentations in the Apulia Region, Italy Food Microbiol
This work is the first large-scale study on vineyard-associated yeast strains from Apulia (Southern Italy).
Yeasts were identified by Internal Transcribed Spacer (ITS) ribotyping and bioinformatic analysis. The
polymorphism of interdelta elements was used to differentiate Saccharomyces cerevisiae strains. Twenty
different species belonging to 9 genera were identified. Predominant on the grape surface were
Metschnikowia pulcherrima, Hanseniaspora uvarum and Aureobasidium pullulans, whereas M. pulcherrima
and H. uvarum were dominant in the early fermentation stage. A total of 692 S. cerevisiae isolates were
identified and a number of S. cerevisiae strains, ranging from 26 to 55, was detected in each of the eight
fermentations. The strains were tested for biogenic amines (BAs) production, either in synthetic media or
grape must. Two Pichia manshurica, an Issatchenkia terricola and a M. pulcherrima strains were able to
produce histamine and cadaverine, during must fermentation. The production of BAs in wine must was
different than that observed in the synthetic medium. This feature indicate the importance of an âin
grape mustâ assessment of BAs producing yeast. Overall, our results suggest the importance of microbiological
control during wine-making to reduce the potential health risk for consumer represented by
these spoilage yeasts
Biodegradation of Ochratoxin A by Bacterial Strains Isolated from Vineyard Soils
Ochratoxin A (OTA) is a mycotoxin with a main nephrotoxic activity contaminating several foodstuffs. In the present report, five soil samples collected from OTA-contaminated vineyards were screened to isolate microorganisms able to biodegrade OTA. When cultivated in OTA-supplemented medium, OTA was converted in OTα by 225 bacterial isolates. To reveal clonal relationships between isolates, molecular typing by using an automated rep-PCR system was carried out, thus showing the presence of 27 different strains (rep-PCR profiles). The 16S-rRNA gene sequence analysis of an isolate representative of each rep-PCR profiles indicated that they belonged to five bacterial genera, namely Pseudomonas, Leclercia, Pantoea, Enterobacter, and Acinetobacter. However, further evaluation of OTA-degrading activity by the 27 strains revealed that only Acinetobacter calcoaceticus strain 396.1 and Acinetobacter sp. strain neg1, consistently conserved the above property; their further characterization showed that they were able to convert 82% and 91% OTA into OTα in six days at 24 °C, respectively. The presence of OTα, as the unique OTA-degradation product was confirmed by LC-HRMS. This is the first report on OTA biodegradation by bacterial strains isolated from agricultural soils and carried out under aerobic conditions and moderate temperatures. These microorganisms might be used to detoxify OTA-contaminated feed and could be a new source of gene(s) for the development of a novel enzymatic detoxification system
Simultaneous inoculation of yeasts and lactic acid bacteria: Effects on fermentation dynamics and chemical composition of Negroamaro wine
Traditional vinification process is undertaken with the inoculation of the lactic acid bacteria (LAB) at the end of alcoholic fermentation (AF) to induce malolactic fermentation (MLF). MLF is an important phase during winemaking and the LAB co-inoculation with yeast starter represents a promising approach to enhance the quality and safety of wine. In this investigation we have studied: i) the effect of timing of LAB inoculation on the vinification dynamics and chemical features of Negroamaro wines; ii) the interactions between two commercial yeast and two commercial Oenococcus oeni strains. The fermentations dynamics were monitored by microbial counts, quantifying l-malic acid concentration and analyzing the volatile compounds contents in the obtained wines. Our results indicate that simultaneous yeasts/bacteria inoculation at the beginning of vinification reduces the processes duration and simultaneously lowers of volatile acidity. Wine obtained after co-inoculum showed a profile dominated by red and ripe fruits notes associated to esters and to buttery and creamy notes linked to diethyl succinate and ethyl lactate. Furthermore, compatibility specification between commercial yeasts and LAB strains were observed, suggesting the importance of the assessment of microbial-compatibility before their utilization in large-scale vinification
Occurrence of Listeria monocytogenes and Salmonella spp. in meat processed products from industrial plants in Southern Italy
The main goal of the present investigation was to assess the microbiological safety of two typical meat-derived products, i.e. raw pork sausages and entrails lamb rolls, produced in Salento (Apulia, Southern Italy). Analyses were carried out for 7 years (from 2008 to 2014) and a total number of 6720 samples was collected by specialized personnel. The presence of Listeria monocytogenes and Salmonella spp. was detected by a PCR-based assay, combined with culturing in enrichment broth. The prevalence of L. monocytogenes was assessed in 2.4% entrails lamb rolls and in 4.2% raw pork sausages samples, whereas the occurrence of Salmonella spp. was revealed in 2.7% lamb rolls and in 3.5% pork sausages. A statistically significant seasonal variation was found in the occurrence of L. monocytogenes; in fact a higher number of samples contaminated by this pathogen was recorded in spring and autumn. On the contrary, no significant seasonal changes occurred in the prevalence of Salmonella spp. The data reported indicate that, due to the presence of these pathogens, the Italian food processors need to improve the microbiological monitoring of the processing chains, in order to guarantee health safety
An innovative oligonucleotide microarray to detect spoilage microorganisms in wine
The aim of this investigation has been the design and validation of an oligonucleotide microarray in order to detect 17 different wine-spoilage microorganisms, i.e. 9 yeasts, 5 lactic bacteria and 3 acetic acid bacteria species. Furthermore, several strains belonging to these species has been found to produce undesirable compounds for wine consumers. Oligonucleotide probes specific for each microorganism were designed to target the intergenic spacer regions (ISR) between 18S-5.8S region for yeasts and 16S-ITS1 region for bacteria. Prior to hybridization the ISR were amplified by polymerase chain reactions using designed consensus primers. Each oligonucleotide-probes exclusively recognized its target without undesired aspecific cross-hybridizations. Under our experimental condition, the microarray assay analysis was able to detect the amount of DNA equivalent to 24 (Saccharomyces cerevisiae), 160 (Lactobacillus brevis) and 124 (Gluconobacter oxydans) cells, three species chosen as experimental models for the three studied microbial classes. Moreover, a novel procedure that allowed the extraction of genomic DNA from a mixture of eukaryotic and prokaryotic cells from contaminated wine was developed. The obtained results confirm that the microarray assay is able to detect specifically different spoilage microorganisms present in mixture in contaminated wines. For the first time the microarray methodology has been applied for the simultaneous identification of different mixed population of spoilage yeast and bacteria directly isolated from wine, thus indicating the practicability of oligonucleotide microarrays as a contamination control in wine industry