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Abstract In this study we investigated how cell origin could affect the efficacy of an antimicrobial treatment (mild heating combined with terpenoids) in Listeria monocytogenes Scott A, considering cells from: 1. single colony, 2. glycerol stock, 3. cold adapted culture, and 4. fresh culture in stationary phase. After treatment, culturability on BHI medium and viability assessed by flow cytometry were evaluated. Our results showed that the cell origin significantly impacted viability and culturability of L. monocytogenes towards antimicrobial treatment. The mild heat treatment combined or not with terpenoids mainly affected culturability rather than viability, although the culturability of cells from single colony was less impacted. Therefore, to mimic the worst scenario, these latter were selected to contaminate Gorgonzola rind and roast beef slices and we evaluated the ability of L. monocytogenes cells to recover their culturability (on ALOA agar medium) and to growth on the food matrix stored at 4 °C for 7 days. Our results suggest that only Gorgonzola rind allowed a partial recovery of the culturability of cells previously heated in presence or not of terpens. In conclusion, we found a connection between the cell history and sensitivity toward an antimicrobial treatment, underlying the importance to standardize the experimental procedures (starting from the cells to be used in the assay) in the assessment of cell sensitivity to a specific treatment. Finally, our study clearly indicated that VBNC cells can resuscitate under favorable conditions on a food matrix, becoming a threat for consumer’s health.

The use of starter cultures in the meat industry is common, even if the number of available commercial cultures is limited, inducing product standardisation and microbial diversity reduction. On the other hand, some artisanal products relying on spontaneous fermentation can represent a source of isolation of new interesting strains. In this work, four LAB strains derived from Mediterranean spontaneously fermented sausages were tested as new starter cultures for the industrial production of fermented sausages, in comparison to a commercial starter culture. The products obtained were analysed for physico-chemical parameters, microbiota, biogenic amines and aroma profile. A consumer test was also performed to evaluate product acceptability. The strains induced different acidification kinetics. LAB counts showed high persistence when Latilactobacillus curvatus HNS55 was used as the starter culture, while the addition of Companilactobacillus alimentarius CB22 resulted in a high concentration of enterococci (6 log CFU/g), 2 log higher than in other samples. Tyramine was detected at concentrations of 150–200 mg/kg, except for in the sample produced with Lactiplantibacillus plantarum BPF2 (60 mg/kg). Differences were observed in the aroma profile, with a high amount of 2-butanone found in the samples obtained with Comp. alimentarius CB22. These latter sausages also showed the lowest score in terms of acceptability. This study allowed us to select new LAB strains for fermented sausage starter cultures, increasing the product diversification. [ABSTRACT FROM AUTHOR]

Fermented nut-based products, obtained after soaking and fermentation, are gaining increasing interest as animal food substitutes because of ethical, environmental and health reasons. In these products, Lactic Acid Bacteria (LAB) perform the fermentation, leading to matrix acidification and contributing to controlling spoilage and pathogenic microbiota. In this work, LAB strains isolated from an artisanal product and combined with a commercial strain were added as starter cultures during nut soaking to produce a cheese-like fermented plant-based product. Three different LAB consortia were used in challenge tests at laboratory scale against Listeria monocytogenes, Escherichia coli or Salmonella Enteritidis, inoculated in nuts at 5 log CFU/g, and monitored for pathogen survival and matrix acidification. The combination of Lactiplantibacillus plantarum 82 and Leuc. carnosum 4010 resulted in faster acidification (pH value < 4.4 after 18 h instead of 48 h) and the reduction of target pathogens; L. monocytogenes was already absent after seven days from production, and the counts of E. coli or S. Enteritidis were lower with respect to other samples. Thus, this microbial consortium was used for a pilot-scale production in which, beyond safety, the fermented plant-based product was also characterized for aroma profile and phenolic compounds, parameters that are known to be affected by LAB fermentation. The results showed an enhancement of the aroma profile, with an accumulation of molecules able to confer cheese-like notes (i.e., acetoin and diacetyl) and higher phenolic content, as well as the presence of compounds (i.e., phenyllactic acid and hydroxyphenyllactic acid) that could exert antimicrobial activity. This study allowed us to set up a guided fermentation for a cheese-like vegan product, guaranteeing safety and improving aromatic and functional features. [ABSTRACT FROM AUTHOR]

Pedodiversity is generally neglected in studies concerning soil organic carbon (SOC). Therefore, this investigation aimed to explore the effect of soil types on the following: (1) soil processes related to organic matter (OM) dynamics along the profile; and (2) the microbial community and functionality within the uppermost horizon. Humic Dystrudepts (HD), Typic Dystrudepts (TD), and Humic Lithic Dystrudepts (HLD) were selected in beech forests of the Apennine ridge in the Emilia-Romagna Region (Italy). Soils were sampled by horizons until parent material, and physico-chemical and functional analyses were performed. The results showed that both HD and HLD soils had a higher SOC accumulation than TD, particularly within the deeper horizons. Such accumulation might be due to the lower turnover rate of soil OM forms, namely fulvic acid-like substances, humic acid-like substances, and non-extractable OM. Noteworthy, the A horizons showed slight differences in SOC among the soil types, suggesting similar SOC decomposition processes. This fact was confirmed by the lack of differences in microbial DNA-based diversity and functionality. This study highlighted the importance of combining pedodiversity and microbial diversity for a wider perspective on SOC dynamics. [ABSTRACT FROM AUTHOR]