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Despite the general classification of L. monocytogenes strains as equally virulent by global safety authorities, molecular epidemiology reveals diverse subtypes in food, processing environments, and clinical cases. This study focuses on a highly virulent strain associated with a listeriosis outbreak in Italy in 2022, providing insights through comprehensive foodomics approaches, with a specific emphasis on quantitative proteomics. In particular, the ST155 strain of L. monocytogenes strain was subjected in vitro to growth stress conditions (NaCl 2.4 %, pH 6.2, T 12 °C), mimicking the conditions present in the frankfurter, its original source. Then, the protein expression patterns were compared with those obtained in optimal growth conditions. Through quantitative proteomic analysis and bioinformatic assessment, different proteins associated with virulence during the exponential growth phase were identified. This study unveils unique proteins specific to each environment, providing insights into how L. monocytogenes adapts to conditions that are similar to those encountered in frankfurters. This investigation contributes valuable insights into the adaptive strategies of L. monocytogenes under stressful conditions, with implications for enhancing food safety practices., Competing Interests: Declaration of competing interest The authors have no conflicts of interest to declare., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Thirty-nine strains of Kluyveromyces marxianus from Pecorino di Farindola cheese in comparison with 3 strains from Parmigiano Reggiano cheese, 1 from fermented milk, 3 from cow whey and two type strains K. marxianus CBS 834(T) and Kluyveromyces lactis CBS 683(T) were tested for genetic and metabolic characteristics. Intraspecific diversity of chromosome arrangements was evaluated by pulsed field gel electrophoresis (PFGE) analysis. Among K. marxianus strains chromosome polymorphisms were evident with 11 patterns that differed in size and number of the chromosomal bands. The number of the bands varied from 4 to 7 with sizes ranging from about 1.0 to 2.7 Mb. Twelve strains were selected for determining their growth capacity and volatile compound production in two wheys (raw cheese whey and ricotta cheese whey) under limited oxygen availability. The growth kinetics highlighted four different biotypes and the influence of whey composition on K. marxianus development. The main volatile compounds detected after the growth were alcohols, acids, esters, ketones and aldehydes. Ethanol was the most abundant in both wheys. Aldehydes and other minor compounds were produced only when the strains were inoculated in ricotta cheese whey, while esters, butanoic, decanoic and octanoic acids were qualitatively and quantitatively more present in raw cheese whey. This study highlights a great genetic and metabolic biodiversity within Pecorino di Farindola K. marxianus strains and it could be exploited to improve the knowledge of this yeast for biotechnological uses., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Twenty-eight flocculent wine strains were tested for adhesion and flocculation phenotypic variability. Moreover, the expression patterns of the main genes involved in flocculation (FLO1, FLO5 and FLO8) were studied both in synthetic medium and in presence of ethanol stress. Molecular identification and typing were achieved by PCR-RFLP of the 5.8S ITS rRNA region and microsatellite PCR fingerprinting, respectively. All isolates belong to Saccharomyces cerevisiae species. The analysis of microsatellites highlighted the intraspecific genetic diversity of flocculent wine S. cerevisiae strains allowing obtaining strain-specific profiles. Moreover, strains were characterized on the basis of adhesive properties. A wide biodiversity was observed even if none of the tested strains were able to form biofilms (or 'mats'), or to adhere to polystyrene. Moreover, genetic diversity of FLO1 and FLO5 flocculating genes was determined by PCR. Genetic diversity was detected for both genes, but a relationship with the flocculation degree was not found. So, the expression patterns of FLO1, FLO5 and FLO8 genes was investigated in a synthetic medium and a relationship between the expression of FLO5 gene and the flocculation capacity was established. To study the expression of FLO1, FLO5 and FLO8 genes in floc formation and ethanol stress resistance qRT-PCR was carried out and also in this case strains with flocculent capacity showed higher levels of FLO5 gene expression. This study confirmed the diversity of flocculation phenotype and genotype in wine yeasts. Moreover, the importance of FLO5 gene in development of high flocculent characteristic of wine yeasts was highlighted. The obtained collection of S. cerevisiae flocculent wine strains could be useful to study the relationship between the genetic variation and flocculation phenotype in wine yeasts., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Pecorino di Farindola is a handicraft cheese made by farmers on small scale using raw ewes' milk and pig rennet. In this study, yeast consortia were evaluated during Pecorino di Farindola making and ripening. Molecular identification of 156 isolates was achieved by a combination of PCR-RFLP of the 5.8S ITS rRNA region and sequencing of the D1/D2 domain of the 26S rRNA gene. Kluyveromyces marxianus was the predominant species, while other species (Pichia kudriavzevii, Candida parapsilosis, Candida glaebosa and Candida zeylanoides) were present only during the early weeks of ripening. Moreover, the isolates were differentiated both by RAPD-PCR and a sequence alignment of D1/D2 26S rRNA gene, revealing different K. marxianus profiles and variants, and suggesting the role of local selective pressure as the origin of distinctive K. marxianus populations. The strains were characterized also on the basis of different dairy properties such as growth temperature, lactose, galactose, lactate and citrate assimilation at different NaCl concentrations, as well as lipolytic and caseinolytic activities. Moreover, 39 selected K. marxianus strains were inoculated in pasteurized whey to evaluate their growth kinetics, besides lactose, lactate and free amino acids metabolism. The growth kinetics distinguished different biotypes and different metabolic behavior were determined. The general picture of K. marxianus population from Pecorino di Farindola shows a high biodiversity at genetic and phenotypic levels that potentially offers many opportunities for new and advanced knowledge at species level, providing in the meantime a good basis to study the relationship between genetic variability and functional diversities., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The yeast communities associated with the fermentation of six different cultivars of Italian table olives were studied. Molecular identification of a total of 117 isolates was achieved by a combination of PCR-RFLP of the 5.8S ITS rRNA region and sequencing of the D1/D2 domain of the 26S rRNA gene. In addition, the isolates were differentiated by RAPD-PCR. The yeast population was also monitored by a culture-independent method based on PCR-DGGE analysis. This combined strategy resulted to be a powerful and reliable tool to investigate table olives yeast ecology and revealed that Saccharomyces cerevisiae was present in all the processed olives. Moreover, strains were characterized on the basis of different properties of technological interest. In particular, β-glucosidase, catalase, pectinolytic, xylanolytic, esterase and lipase activities were investigated and the ability to grow up in presence of different salt concentration (5-7.5-10-14-20% w/v) was evaluated. The majority of strains showed catalase activity and none of them expressed pectinolytic, xylanolytic, esterase or lipase activities. Six strains belonging to Pichia galeiformis and six strains of Wicheramomyces anomalus showed β-glucosidase activity. Only 10 S. cerevisiae strains were able to grow in presence of 14% NaCl. The obtained results offer valuable information on yeast population biodiversity and dynamics in naturally fermented Italian table olives and show the potential use of some yeast strains, besides lactic acid bacteria, as a part of mixed starter cultures for table olive fermentation., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Yeasts isolated from Italian beverages and foods (wine and cheeses) were identified as Saccharomyces cerevisiae and Debaryomyces hansenii by sequencing the D1/D2 domain of the 26S rRNA gene and differentiated, at strain level, by microsatellite PCR fingerprinting and RAPD-PCR. All the strains showed antioxidant activity, as demonstrated by their ability to scavenge the free radical diphenyl-1-picrylhydrazyl (DPPH). Furthermore, tested strains revealed high in vitro inhibitory activity against two model genotoxins, 4-nitroquinoline-1-oxide (4-NQO) and N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), as showed by short-term methods with different target cells: SOS-Chromotest with Escherichia coli PQ37 and Comet assay with HT-29 enterocytes. High inhibitory activity towards 4-NQO was associated with cell viability, while heat-inactivated cells showed a reduced antigenotoxic capability. Surprisingly, high inhibition of MNNG genotoxicity was observed even with heat-treated cells. Moreover, the strains able to inhibit the genotoxins induced some changes in the spectroscopic properties of the original compound. This result perfectly agrees with the information obtained by the two bioassays. Interestingly, strains characterized for antioxidant and antigenotoxic properties, also presented acid-bile tolerance, indicating that food autochthonous yeasts could be expected to reach gut in viable form and thus prevent genotoxin DNA damage in situ., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The objective of this study was to examine the Saccharomyces and non-Saccharomyces yeast populations involved in a spontaneous fermentation of a traditional high sugar must (Vino cotto) produced in central Italy. Molecular identification of a total of 78 isolates was achieved by a combination of PCR-RFLP of the 5.8S ITS rRNA region and sequencing of the D1/D2 domain of the 26S rRNA gene. In addition, the isolates were differentiated by RAPD-PCR. Only a restricted number of osmotolerant yeast species, i.e. Candida apicola, Candida zemplinina and Zygosaccharomyces bailii, were found throughout all the fermentation process, while Saccharomyces cerevisiae prevailed after 15 days of fermentation. A physiological characterization of isolates was performed in relation to the resistance to osmotic stress and ethanol concentration. The osmotolerant features of C. apicola, C. zemplinina and Z. bailii were confirmed, while S. cerevisiae strains showed three patterns of growth in response to different glucose concentrations (2%, 20%, 40% and 60% w/v). The ability of some C. apicola and C. zemplinina strains to grow at 14% v/v ethanol is noteworthy. The finding that some yeast biotypes with higher multiple stress tolerance can persist in the entire winemaking process suggests possible future candidates as starter for Vino cotto production.