The population dynamics of pseudomonads in gilt-head sea bream Mediterranean fish (Sparus aurata) stored under different conditions were studied. Phenotypic analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell proteins were performed to identify a total of 106 Pseudomonas strains isolated from S. aurata stored under different temperatures (at 0, 10, and 20°C) and packaging conditions (air and a modified atmosphere of 40% CO 2 -30% N 2 -30% O 2 ). Pseudomonas lundensis was the predominant species, followed by Pseudomonas fluorescens, while Pseudomonas fragi and Pseudomonas putida were detected less frequently. Fluorescent Pseudomonas strains dominated under air conditions, while proteolytic and less lipolytic strains dominated under modified-atmosphere packaging. Different storage conditions appear to govern the selection of pseudomonads in gilt-head sea bream fish.It is well known that fish spoilage is primarily due to (i) autolysis, (ii) bacterial growth and metabolism resulting in the formation of off-flavor compounds, and (iii) chemical oxidation of lipids. Among these reasons, microbiological activity is by far the most important factor influencing fish quality (22). However, not all microorganisms in seafood are equally important for quality changes. Fish feeding habits, geographical location, season, sea temperature, type of fish, place in which the fish were harvested, and storage conditions, including temperature and composition of the packaging atmosphere, determine the spoilage domains of specific spoilage organisms (SSO) (22,36).Photobacterium phosphoreum, Shewanella putrefaciens, Brochothrix thermosphacta, Pseudomonas spp., Aeromonas spp., and lactic acid bacteria were found to be members of the microbial association in fish from temperate waters (12, 32). However, among these, only S. putrefaciens was the SSO of marine cold-water fish stored in ice, while P. phosphoreum was the SSO of fish stored under modified-atmosphere conditions. On the other hand, Pseudomonas spp. and Shewanella spp. were found to be the SSO in fish obtained from Mediterranean Sea temperate waters and stored in ice aerobically (32). In comparison to data for meat and meat products (19,45,57), identification and characterization of SSO in fish under different storage conditions have not been sufficiently studied. This situation is especially evident with Pseudomonas spp., a group with high heterogeneity and biodiversity within species and/or subspecies. Furthermore, many pseudomonad groups have no clear taxonomic status or natural relationships with other genera (44,47,48,49).For both of the reasons mentioned above, the use of conventional phenotypic methods can offer only limited results (6, 9, 42). In contrast, molecular methods are powerful tools not only for identification at the species level but also for strain characterization (7,14,29,30,63). Although molecular fingerprinting methods have been successfully applied for bacteria of medical interest in epidemiological studies, they are not al...

Indeed, Shewanella putrefaciens, Pseudomonas spp., Photobacterium phosphoreum, Brochothrix thermosphacta, Aeromonas spp. and lactic acid bacteria are not only members of the microbial association found in fish from temperate waters (Koutsoumanis and Nychas 1999;Dalgaard 2000), but they also contribute significantly to the spoilage of fish stored under different conditions. However, not all Keywords 16S rRNA, fish preservation, fish spoilage, modified atmosphere packaging, sodium dodecyl sulfate electrophoresis, taxonomy. AbstractAims: To study the diversity of Shewanella population in Sparus aurata fish harvested in the Aegean Sea, as well as to elucidate the influence of fish storage conditions on the selection in Shewanella strains. Methods and Results: A total of 108 strains of Shewanella spp. were isolated from Sparus aurata during storage under various conditions. Conventional phenotypic analysis along with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of whole cell proteins and 16S rRNA sequence analysis were used for the characterization of the strains. Numerical analysis of whole cell protein profiles showed that the isolates were separated into two distinct clusters A and B with 47% similarity. Cluster B was further subdivided into two subclusters B1 and B2 with 70% similarity. One strain could not be assigned to any of these groups. The different ability of isolates to utilize deoxycholate, d-saccharate, d-glucuronate, n-acetyl-glycosamine, d-maltose, gluconate and citrate, as well as the different type of metabolism on the Hugh and Leifson medium distinguished the different Shewanella biogroups, as these were defined by the SDS-PAGE analysis. Representative strains from the three biogroups were further investigated by 16S rRNA sequence analysis and showed more than 99AE4% similarity. Conclusions: Significant similarities between the isolates and the type strains of S. baltica, S. putrefaciens and S. oneidensis at both phenotypic and molecular level signalize that the new isolates are closely related with the above Shewanella species, but do not provide a clear evidence to which of these species they belong. Significance and Impact of the Study: The lack of information about the diversity of Shewanella population in Sparus aurata fish originated from Mediterranean Sea could be confronted using conventional phenotypic techniques, SDS-PAGE analysis of whole cell proteins and 16S rRNA sequencing.

Aims To assess the ability of various newly isolated or belonging in official collections yeast strains to convert biodiesel‐derived glycerol (Gly) into added‐value compounds. Methods and Results Ten newly isolated yeast strains belonging to Debaryomyces sp., Naganishia uzbekistanensis, Rhodotorula sp. and Yarrowia lipolytica, isolated from fishes, metabolized Gly under nitrogen limitation. The aim of the study was to identify potential newly isolated microbial candidates that could produce single‐cell oil (SCO), endopolysaccharides and polyols when these micro‐organisms were grown on biodiesel‐derived Gly. As controls producing SCO and endopolysaccharides were the strains Rhodotorula glutinis NRRL YB‐252 and Cryptococcus curvatus NRRL Y‐1511. At initial Gly (Gly0) ≈40 g l−1, most strains presented remarkable dry cell weight (DCW) production, whereas Y. lipolytica and Debaryomyces sp. produced non‐negligible quantities of mannitol and arabitol (Ara). Five strains were further cultivated at increasing Gly0 concentrations. Rhodotorula glutinis NRRL YB‐252 produced 7·2 g l−1 of lipid (lipid in DCW value ≈38% w/w), whereas Debaryomyces sp. FMCC Y69 in batch‐bioreactor experiment with Gly0 ≈80 g l−1, produced 30–33 g l−1 of DCW and ~30 g l−1 of Ara. At shake‐flasks with Gly0 ≈125 g l−1, Ara of ~48 g l−1 (conversion yield of polyol on Gly consumed ≈0·62 g g−1) was achieved. Cellular lipids of all yeasts contained in variable concentrations oleic, palmitic, stearic and linoleic acids. Conclusions Newly isolated, food‐derived and non‐previously studied yeast isolates converted biodiesel‐derived Gly into several added‐value metabolites. Significance and Impact of the Study Alternative ways of crude Gly valorization through yeast fermentations were provided and added‐value compounds were synthesized.

To our knowledge this is the first report on the development of an HRM-PCR assay for the identification of black Aspergillus species in grape samples. © 2018 Society of Chemical Industry.

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