Maria Barbara Pisano

A NMR metabolomics study of the ripening process of the Fiore Sardo cheese produced with autochthonous adjunct cultures

Fiore Sardo (FS) is a traditional Italian raw ewes milk cheese carrying a Protected Designation of Origin (PDO). This study investigated the kinetics of FS cheese ripening by physicochemical parameters, microbial counting, and NMR metabolomics using aqueous extracts. Four Fiore Sardo cheeses, manufactured from milk with deliberately added autochthonous lactic acid bacteria (LAB) or commercial starters were studied during a period of 90days of ripening. Major differences in the metabolic profiles were observed amongst the samples as a function of the adjunct culture utilised. (1)H NMR metabolomics in combination with multivariate data analysis was able to classify cheese samples on the basis of their maturation age and the type of added cultures. These findings lay the metabolic basis for the authentication of Fiore Sardo cheese produced in compliance with PDO specifications which allow the use of only native LAB cultures.

Characterization of yeast population and molecular fingerprinting of Candida zeylanoides isolated from goat's milk collected in Sardinia

The occurrence of yeast microflora in raw goats milk collected from 62 dairy farms located in different areas of Sardinia was evaluated. Candida zeylanoides was the most frequently occurring species followed by different Basidiomycetous species. In the strains isolated some biochemical characteristics of technological interest were investigated and a predominance of lipolytic yeast species was found. We employed a simple method of DNA extraction that in a minimal time and with low-cost provided a high quality of DNA for RAPD analysis of 32 isolates of C. zeylanoides. The primers M13 and CDU were used and at 40% of similarity, two distinct clusters were observed. The presence of C. krissii species was supposed but further molecular studies are needed to exclude the presence of an as-yet-undescribed species.

Preliminary Evaluation of Probiotic Properties of Lactobacillus Strains Isolated from Sardinian Dairy Products

Twenty-three Lactobacillus strains of dairy origin were evaluated for some functional properties relevant to their use as probiotics. A preliminary subtractive screening based on the abilities to inhibit the growth of microbial pathogens and hydrolyze conjugated bile salts was applied, and six strains were selected for further characterization including survival under gastrointestinal environmental conditions, adhesion to gut epithelial tissue, enzymatic activity, and some safety properties. All selected strains maintained elevated cell numbers under conditions simulating passage through the human gastrointestinal tract, well comparable to the values obtained for the probiotic strain Lactobacillus rhamnosus GG, and were able to adhere to Caco-2 cells to various extents (from 3 to 20%). All strains exhibited high aminopeptidase, and absent or very low proteolytic and strong β-galactosidase activities; none was found to be haemolytic or to produce biogenic amines and all were susceptible to tetracycline, chloramphenicol, erythromycin, ampicillin, and amoxicillin/clavulanic acid. Our results indicate that the Lactobacillus strains analyzed could be considered appropriate probiotic candidates, due to resistance to GIT simulated conditions, antimicrobial activity, adhesion to Caco-2 cell-line, and absence of undesirable properties. They could be used as adjunct cultures for contributing to the quality and health related functional properties of dairy products.

Metabolomics and microbiological profile of Italian mozzarella cheese produced with buffalo and cow milk

Italian buffalo mozzarella (BM) cheese metabolite profile and microbial communities were characterised and compared to cow mozzarella (CM). Polar metabolite profiles were studied by gas-chromatography mass-spectrometry (GC-MS) and results elaborated by multivariate analysis (MVA). BM produced using natural whey starter cultures (NWS) exhibited a higher microbial diversity with less psychrotrophic bacteria. BM samples were higher in threonine, serine, valine, and lower in orotic acid and urea. CM produced with commercial starters (CMS) had the highest count of Streptococcus thermophilus and higher levels of galactose and phenylalanine. CM obtained by direct acidification (CMA) had lower microbial counts and higher levels of urea and sugars. Orotic acid was the only metabolite linked to milk animal origin. Results indicated that this metabolite pool well reflects the different production protocols and microbial complexity of these dairy products. This approach can help to protect the designation of origin of Italian buffalo mozzarella.

Antilisterial activity of nisin-like bacteriocin producing Lactococcus lactis subsp. lactis isolated from traditional sardinian dairy products.

With the aim of selecting LAB strains with antilisterial activity to be used as protective cultures to enhance the safety of dairy products, the antimicrobial properties of 117 Lactococcus lactis subsp. lactis isolated from artisanal Sardinian dairy products were evaluated, and six strains were found to produce bacteriocin-like substances. The capacity of these strains to antagonize Listeria monocytogenes during cocultivation in skimmed milk was evaluated, showing a reduction of L. monocytogenes counts of approximately 4 log units compared to the positive control after 24 h of incubation. In order for a strain to be used as bioprotective culture, it should be carefully evaluated for the presence of virulence factors, to determine what potential risks might be involved in its use. None of the strains tested was found to produce biogenic amines or to possess haemolytic activity. In addition, all strains were sensitive to clinically important antibiotics such as ampicillin, tetracycline, and vancomycin. Our results suggest that these bac+ strains could be potentially applied in cheese manufacturing to control the growth of L. monocytogenes.

Metabolomics analysis of shucked mussels’ freshness

In this work a NMR metabolomics approach was applied to analyze changes in the metabolic profile of the bivalve mollusk Mytilus galloprovincialis upon storage at 0°C and 4°C for 10 and 6 days, respectively. The most significant microbial groups involved in spoilage of mussels were also investigated. The time-related metabolic signature of mussels was analysed by Orthogonal Partial Least Squares Discriminant Analysis (OPLS-DA) which revealed a clear discrimination between the fresh samples and those stored at 0°C and 4°C. The results evidenced a noticeable increase in acetate, lactate, succinate, alanine, branched chain amino acids, trimethylamine and a progressive decline of osmolytes like betaine, homarine and taurine during storage. Exploration of the correlations of these metabolites with microbial counts suggested their use as potential biomarkers of spoilage. The results support the use of NMR metabolomics as a valuable tool to provide information on seafood freshness.

Chitinase III in Euphorbia characias latex: Purification and characterization

This paper deals with the purification of a class III endochitinase from Euphorbia characias latex. Described purification method includes an effective novel separation step using magnetic chitin particles. Application of magnetic affinity adsorbent noticeably simplifies and shortens the purification procedure. This step and the subsequently DEAE-cellulose chromatography enable to obtain the chitinase in homogeneous form. One protein band is present on PAGE in non-denaturing conditions and SDS-PAGE profile reveals a unique protein band of 36.5 ± 2 kDa. The optimal chitinase activity is observed at 50 °C, pH 5.0. E. characias latex chitinase is able to hydrolyze colloidal chitin giving, as reaction products, N-acetyl-D-glucosamine, chitobiose and chitotriose. Moreover, we observed that calcium and magnesium ions enhance chitinase activity. Finally, we cloned the cDNA encoding the E. characias latex chitinase. The partial cDNA nucleotide sequence contains 762 bp, and the deduced amino acid sequence (254 amino acids) is homologous to the sequence of several plant class III endochitinases.

Biological activities of aerial parts extracts of Euphorbia characias

The aim of the present study was to evaluate antioxidant, antimicrobial, anti-HIV, and cholinesterase inhibitory activities of aqueous and alcoholic extracts from leaves, stems, and flowers of Euphorbia characias. The extracts showed a high antioxidant activity and were a good source of total polyphenols and flavonoids. Ethanolic extracts from leaves and flowers displayed the highest inhibitory activity against acetylcholinesterase and butyrylcholinesterase, showing potential properties against Alzheimers disease. Antimicrobial assay showed that leaves and flowers extracts were active against all Gram-positive bacteria tested. The ethanolic leaves extract appeared to have the strongest antibacterial activity against Bacillus cereus with MIC value of 312.5 μg/mL followed by Listeria monocytogenes and Staphylococcus aureus that also exhibited good sensitivity with MIC values of 1250 μg/mL. Moreover, all the extracts possessed anti-HIV activity. The ethanolic flower extract was the most potent inhibitor of HIV-1 RT DNA polymerase RNA-dependent and Ribonuclease H with IC50 values of 0.26 and 0.33 μg/mL, respectively. The LC-DAD metabolic profile showed that ethanolic leaves extract contains high levels of quercetin derivatives. This study suggests that Euphorbia characias extracts represent a good source of natural bioactive compounds which could be useful for pharmaceutical application as well as in food system for the prevention of the growth of food-borne bacteria and to extend the shelf-life of processed foods.

Lipid components and water soluble metabolites in salted and dried tuna (Thunnus thynnus L.) roes

The salted and dried product of tuna roe (bottarga) is a seafood characteristic of the Mediterranean area and exported all over the world. Samples of bottarga from bluefin tunas (Thunnus thynnus, L.) caught in the southwest Mediterranean sea were analysed. The samples were characterised by high content of marine wax esters (55-67 mol% of lipid classes), of docosahexaenoic (22:6 n-3, 25 w%) and oleic (18:1 n-9, 19 w%) fatty acids. Cholesterol was detected as 7-9 w% of lipids. Free fatty acids, index of lipid hydrolysis, represented 32-39 mol% over total fatty acids. Among metabolites, nutrients as taurine, nicotinamide and β-alanine, were found. The microflora comprised staphylococci, enterococci (2.2 log(10)CFU/g) and lactic acid bacteria (3 log(10) CFU/g). The food-borne pathogens Staphylococcus aureus, Listeria monocytogenes and Salmonella spp. were not detected. These findings indicate tuna bottarga as valuable source of nutrients.

Data on the changes of the mussels' metabolic profile under different cold storage conditions

One of the main problems of seafood marketing is the ease with which fish and shellfish undergo deterioration after death. 1H NMR spectroscopy and microbiological analysis were applied to get in depth insight into the effects of cold storage (4 °C and 0 °C) on the spoilage of the mussel Mytilus galloprovincialis. This data article provides information on the average distribution of the microbial loads in mussels׳ specimens and on the acquisition, processing, and multivariate analysis of the 1H NMR spectra from the hydrosoluble phase of stored mussels. This data article is referred to the research article entitled “Metabolomics analysis of shucked mussels’ freshness” (Aru et al., 2016) [1].