Papers by Simona Campolongo
Journal of the Institute of Brewing, 2011
In this study we investigated the biodiversity of Saccharomyces cerevisiae during the brewing of ... more In this study we investigated the biodiversity of Saccharomyces cerevisiae during the brewing of an artisanal beer, as well as during its storage in the bottle for 107 days at 20°C. After inoculation with an active dried yeast (ADY), the yeast counts were followed during fermentation and after bottling. Yeast loads remained stable at 10 6 -10 7 colony forming units (cfu)/mL, and only after day 21, were they were reduced to 10 4 cfu/mL. After three months in the bottle they spanned 10 2 -10 5 cfu/mL. Almost all isolated yeasts were identified as S. cerevisiae and after molecular characterization, unexpected results were obtained. The ADY did not take over the fermentation process and only after 21 days did isolates from the beer share similarities with the inoculated strain. During storage, a high diversity was found, underlining that each bottle developed its own micro-ecosystem. This study highlighted the necessity for better investigations of S. cerevisiae population dynamics during artisanal brewing. Even when the chemical parameters measured confirmed a correct fermentation process, the inoculated strain was not the main yeast involved in the fermentation and consequently, the final product may have different sensory characteristics from the ones expected by the producers.
LWT - Food Science and Technology, 2014
Brettanomyces bruxellensis yeast produces ethyl phenols, which cause wine spoilage and severe eco... more Brettanomyces bruxellensis yeast produces ethyl phenols, which cause wine spoilage and severe economic losses. Ethyl phenols are produced by a class of polyphenols that are present in grapes and musts, called hydrocinnamic acids, which are capable of inhibiting yeasts and bacteria. The viability and intracellular pH changes in B. bruxellensis DSM 7001, in response to extracellular pH, as well as to the presence of an energy source and hydroxycinnamic acids, have been investigated in this paper by means of Fluorescent Ratio Imaging Microscopy (FRIM). The results show that B. bruxellensis DSM 7001 is able to maintain viability and increase its pH gradient with decreasing external pH values, whereas it is not able to maintain a pH gradient at high external pH values (i.e. pH 8) and, as a consequence, dies. The growth inhibitory effects of ferulic and p-coumaric acid do not seem to be caused by a weak-acid inhibition mechanism, since both acids induce a similar, or even higher, intracellular acidification at a high external pH than at a low external pH. The results presented have to be confirmed by using other strains of B. bruxellensins in order to validate the outcomes obtained in this study.
PROTEOMICS, 2012
The use of Enterococcus faecalis in the food industry has come under dispute because of the patho... more The use of Enterococcus faecalis in the food industry has come under dispute because of the pathogenic potential of some strains of this species. In this study, we have compared the secretome and whole-cell proteome of one food isolate (E. faecalis DISAV 1022) and one clinical isolate (E. faecalis H1) by 2-DE and iTRAQ analyses, respectively. Extracellular protein patterns differed significantly, with only seven proteins common to both strains. Notably, only the clinical isolate expressed various well-characterized virulence factors such as the gelatinase coccolysin (GelE) and the extracellular serine proteinase V8 (SprE). Moreover, various other putative virulence factors, e.g. superoxide dismutase, choline- and chitin-binding proteins and potential moonlighting proteins, have been detected exclusively in the secretome of the clinical isolate, but not in the food isolate. The iTRAQ analysis of whole-cell proteins of the two strains highlighted a stronger expression of pathogenic traits such as an endocarditis-specific antigen and an adhesion lipoprotein in the pathogenic strain E. faecalis H1. Subsequently, six food isolates (including E. faecalis DISAV 1022) and six clinical isolates (including E. faecalis H1) were tested for the presence of gelatinase and protease activity in the culture supernatants. Both enzymatic activities were found in the clinical as well as the food isolates which clearly indicates that protease expression is strain specific and not representative for pathogenic isolates. Genetic analyses revealed that not only the gelatinase and serine protease genes but also the regulatory fsr genes must be present to allow protease expression.
Dalton Transactions, 2009
Catechol 1,2-dioxygenases are iron containing enzymes able to convert catechol into cis,cis-mucon... more Catechol 1,2-dioxygenases are iron containing enzymes able to convert catechol into cis,cis-muconate, a precursor of the industrially important compound adipic acid. Catechol 1,2-dioxygenase from Acinetobacter radioresistens S13 was immobilized on beta-cyclodextrins cross-linked with carbonate groups (nanosponges) with a yield of 29 mg of enzyme per gram of support. This support was chosen for its low cost and its ability to offer different types of interactions with the enzyme. The activity profiles at different pH and temperatures showed a shift of the optimal pH from 8.5, for the free protein, to 9.5, for the immobilized protein and, similarly, a shift in optimal temperature from 30 degrees C to 50 degrees C. The Michaelis-Menten constant, KM, increased from 2.0 +/- 0.3 microM, for the free form, to 16.6 +/- 4.8 microM for the immobilized enzyme, whereas the rate constant, k(cat), values were found to be 32 +/- 2 s(-1) and 27 +/- 3 s(-1) for the free and immobilized forms respectively. The immobilization process also increased the thermostability of the enzyme with 60% residual activity after 90 min at 40 degrees C for the immobilized protein versus 20% for the free enzyme. A residual activity of 75% was found after 15 min at 60 degrees C for the immobilized enzyme while the free form showed a total loss of activity under the same conditions. The activity toward other substrates, such as 3- and 4-methylcatechol and 4-chlorocatechol, was retained by the immobilized enzyme. A small scale bioreactor was constructed and was able to convert catechol into cis,cis-muconic acid with high efficiency for 70 days.
Annals of Microbiology, 2011
Wine fermentations are complex microbial ecosystems, with both yeasts and bacteria taking part in... more Wine fermentations are complex microbial ecosystems, with both yeasts and bacteria taking part in the transformation process with their metabolic activities. Traditional microbiological methods do not allow a complete understanding of the microbial ecology of complex systems. This is due mainly to the capacity of certain microorganisms to grow on microbiological media preferentially with respect to others. Moreover, with these methods, stressed or damaged cells cannot be detected on the plates. In the last 10 years new methods based on the analysis of nucleic acids (DNA and RNA) extracted directly from the sample without the need for microbial cultivation have been developed. A method often used in this type of study is the polymerase chain reaction (PCR) coupled with denaturing gradient gel electrophoresis (DGGE). This paper aims to report the most important contributions of PCR-DGGE to the study of microbiological ecology during wine fermentation.
American Journal of Enology and Viticulture, 2010
ABSTRACT Brettanomyces bruxellensis is a catalyst in the transformation of hydroxycinnamic acids ... more ABSTRACT Brettanomyces bruxellensis is a catalyst in the transformation of hydroxycinnamic acids compounds that naturally occur in grapes producing volatile phenols that reduce the sensory quality of wine Depending on their concentrations volatile phenols can confer off odors described as phenolic animal mousy wet wool medicinal smoky and spicy We used a multidisciplinary approach for the detection and quantification of the presence of B bruxellensis in 87 Italian wines applying culture independent and dependent methods (quantitative PCR and traditional microbiological analysis respectively) Headspace solid phase microextraction was used to quantify ethylphenols and vinylphenols Results showed that there was no correlation between culture dependent and culture independent methods Strain biodiversity was investigated by SAU PCR and showed a differentiation of the isolates based on geographical origin
In this study, attention has been focused on microbial ecology, during an on-vine withering perio... more In this study, attention has been focused on microbial ecology, during an on-vine withering period of 120 days, of Mondeuse grapes, an autochthonous variety cultivated in the Western Alps in Europe, and on their fate during alcoholic fermentation. Laboratory fermentations have been followed in order to describe the yeast dynamics in both spontaneous and inoculated fermentations by means of culture-dependent and -independent methods (PCR-DGGE). The ability of Saccharomyces cerevisiae to take over the fermentation has also been assessed by means of minisatellite analysis. The chemical composition has been evaluated on the final products. A biodiversity of the grapes has been detected during the withering period, despite the predominance of Aureobasidium pullulans and Rhodotorula glutinis thus empathising that withering conditions could affect yeast populations. The spontaneous laboratory fermentation was characterized by a predominance of Hanseniaspora uvarum, Metschnikowia fructicola and S. cerevisiae. In the inoculated ones, counts of S. cerevisiae, belonging to the inoculated starter culture, became predominant after 7 days, even though the PCR-DGGE analysis showed the starter profile for the entire fermentation period. Finally, when the S. cerevisiae isolates were characterized by the minisatellite analysis, it was determined that the inoculated culture was responsible for the alcoholic fermentation. As far as spontaneous fermentation is concerned, the autochthonous S. cerevisiae showed a good ethanol production yield, but left a high concentration of residual sugars.
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Papers by Simona Campolongo