The spoilage of raw meat is mainly due to undesired microbial development in meat during storage. The type of bacteria and their loads depend on the initial meat contamination and on the specific ...storage conditions that can influence the development of different spoilage-related microbial populations thus affecting the type and rate of the spoilage process. This review focuses on the composition of raw meat spoilage microbiota and the influence of storage conditions such as temperature, packaging atmosphere and use of different preservatives on the bacterial diversity developing in raw meat. In addition, the most recent tools used for the detection and identification of meat microbiota are also reviewed.
► The most important microbial species occurring during meat storage are described. ► The effect of different storage conditions on microbial composition of meat is highlighted. ► The principal tools used for the identification of meat microbiota are reviewed.
There is increasing concern about the public health impact of methicillin-resistant Staphylococcus aureus. Food and animal are vectors of transmission, but the contribution of a contaminated ...environment is not well characterized. With regard to this, staphylococcal biofilms serve as a virulence factor, allowing MRSA strains to adhere to surfaces and other materials used in the food industry.
Methicillin resistance and biofilm-forming capacity may contribute to the success of S. aureus as a human pathogen in both health care and community settings and the food production chain. This review summarizes current knowledge about the significance of food- and animal-derived MRSA strains and provides data on attachment and biofilm formation of MRSA. In addition, the impact of quorum sensing on MRSA gene expression and biofilm formation is examined.
Listeria monocytogenes biofilms present a significant challenge in the food industry. This study explores the impact of different acidic conditions of culture media and food matrices on the ...development and removal of biofilms developed on stainless steel surfaces by wild-type (WT) L. monocytogenes strains as well as in two mutant derivatives, ΔsigB and ΔagrA, that have defects in the general stress response and quorum sensing, respectively. Additionally, the study investigates the efficacy of nanoencapsulated carvacrol as an antimicrobial against L. monocytogenes biofilms developed in Tryptic Soy Broth (TSB) culture media acidified to different pH conditions (3.5, 4.5, 5.5, 6.5), and in food substrates (apple juice, strained yogurt, vegetable soup, semi-skimmed milk) having the same pH levels. No biofilm formation was observed for all L. monocytogenes strains at pH levels of 3.5 and 4.5 in both culture media and food substrates. However, at pH 5.5 and 6.5, increased biofilm levels were observed in both the culture media and food substrates, with the WT strain showing significantly higher biofilm formation (3.04–6.05 log CFU cm−2) than the mutant strains (2.30–5.48 log CFU cm−2). For both applications, the nanoencapsulated carvacrol demonstrated more potent antimicrobial activity against biofilms developed at pH 5.5 with 2.23 to 3.61 log reductions, compared to 1.58–2.95 log reductions at pH 6.5, with mutants being more vulnerable in acidic environments. In food substrates, nanoencapsulated carvacrol induced lower log reductions (1.58–2.90) than the ones in TSB (2.02–3.61). These findings provide valuable insights into the impact of different acidic conditions on the development of L. monocytogenes biofilms on stainless steel surfaces and the potential application of nanoencapsulated carvacrol as a biofilm control agent in food processing environments.
•Greater biofilm formation at pH 5.5 and 6.5 in both culture media and food•Nanoencapsulated carvacrol was effective in biofilm removal, especially at pH 5.5.•Mutant L. monocytogenes were more vulnerable in acidic conditions.•Food substrates reduced nanoencapsulated carvacrol's efficacy.
The aim of the present study was to investigate the production of 1,3-propanediol (PDO) under non-sterile fermentation conditions by employing the strain
Clostridium butyricum
VPI 1718. A series of ...batch cultures were performed by utilizing biodiesel-derived crude glycerol feedstocks of different origins as the sole carbon source, in various initial concentrations. The strain presented similarities in terms of PDO production when cultivated on crude glycerol of various origins, with final concentrations ranging between 11.1 and 11.5 g/L. Moreover, PDO fermentation was successfully concluded regardless of the initial crude glycerol concentration imposed (from 20 to 80 g/L), accompanied by sufficient PDO production yields (0.52–0.55 g per gram of glycerol consumed). During fed-batch operation under non-sterile culture conditions, 67.9 g/L of PDO were finally produced, with a yield of 0.55 g/g. Additionally, the sustainability of the bioprocess during a continuous operation was tested; indeed, the system was able to run at steady state for 16 days, during which PDO effluent level was 13.9 g/L. Furthermore, possible existence of a microbial community inside the chemostat was evaluated by operating a polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis, and DGGE results revealed the presence of only one band corresponding to that of
C. butyricum
VPI 1718. Finally, non-sterile continuous cultures were carried out at different dilution rates (
D
), with inlet glycerol concentration at 80 g/L. Maximum PDO production was achieved at low
D
values (0.02 h
−1
) corresponding to 30.1 g/L, while the elaboration of kinetic data from continuous cultures revealed the stability of the bioprocess proposed, with global PDO production yield corresponding to 0.52 g/g.
Celotno besedilo
Dostopno za:
CEKLJ, DOBA, EMUNI, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK
is an important beer-spoiling species, exhibiting high hop tolerance. Here, we present the annotated whole genome sequence of two recently isolated strains,
KKP 3565 and KKP 3566. Firstly, to study ...the genetic basis of the persistence of the two isolates in beer, a comprehensive bioinformatic analysis ensued. Their chromosome map was constructed, using whole-genome sequencing and assembly, revealing that the two strains carry genomes with a length of 2.79 Mb with a GC content of 40.68%. An average nucleotide identity (ANI) analysis demonstrated that the novel strains possess unique genomic sequences, also confirming their classification into the
species. Their genome harbors numerous insertion sequences and plasmids, originating from other beer-spoiling species. Regarding their adaptation in brewery environment, homologous genes that confer resistance to hop were spotted, while the impact of hop bitters and pure beer on bacterial growth was investigated, in vitro. In brief, low hop concentrations were found to induce the proliferation of strains, while a higher concentration negatively affected their growth. Nonetheless, their ability to survive in pure beer indicated their tolerance to high hop concentrations. These results offer insight into the capacity of
KKP 3566 and
KKP 3566 to tolerate the extreme conditions prevalent in the brewery environment.
Feta cheese is the most recognized Greek Protected Designation of Origin (PDO) product in the world. The addition of selected autochthonous lactic acid bacteria (LAB) strains to cheese milk as ...adjunct cultures is gaining more attention, since they can impact the nutritional, technological and sensory properties of cheeses, as well as improve the safety of the product. The aim of this study was to produce Feta cheese with enhanced quality and safety, and distinctive organoleptic characteristics by applying autochthonous lactic acid bacteria (LAB) with multi-functional properties as adjunct cultures. Feta cheeses were produced with the commercial lactococcal starter culture and the addition of 9 LAB strains (
Lactococcus lactis
SMX2 and SMX16
, Levilactobacillus brevis
SRX20
, Lacticaseibacillus paracasei
SRX10,
Lactiplantibacillus plantarum
FRX20 and FB1
, Leuconostoc mesenteroides
FMX3, FMX11, and FRX4, isolated from artisanal Greek cheeses) in different combinations to produce 13 cheese trials (12 Feta trials with the adjunct LAB isolates and the control trial). In addition, Feta cheese manufactured with FMX3 and SMX2 and control Feta cheese were artificially inoculated (4 log CFU/g) with
Listeria monocytogenes
(a cocktail of 4 acid or non-acid adapted strains). Cheese samples were monitored by microbiological and physicochemical analyses during ripening, and microbiological, physicochemical, molecular and sensory analyses during storage at 4°C. The results showed that after manufacture, the LAB population was
ca.
9.0 log CFU/g at all samples, whereas during storage, their population declined to 6.5–7.0 log CFU/g. In the
Listeria
inoculated samples,
Listeria
was absent after 60 days (end of ripening) and after 90 days in the adjunct culture, and in the control trials, respectively. Moreover, the addition of selected strains, especially
Lcb. paracasei
SRX10, led to cheeses with desirable and distinctive organoleptic characteristics. Furthermore, randomly amplified polymorphic PCR (RAPD-PCR) molecular analysis confirmed that the multi-functional LAB strains were viable by the end of storage. Overall, the results of this study are promising for the use of autochthonous strains in various combinations with the commercial starter culture to satisfy industry requirements and consumer demands for traditional and high added value fermented products.
The prevalence of three pathogens in marinated chicken products and the evaluation of their quality by microbiological and sensory analysis were assessed. Eighty (80) samples obtained from several ...meat retail markets in Greece were analyzed for the presence of Campylobacter spp., Salmonella and Listeria monocytogenes. Concerning Campylobacter, rep-PCR and species specific PCR were applied for the differentiation and identification of isolates, respectively. The samples were subsequently stored aerobically at 4 °C for 5 days. Microbiological analysis, sensory assessment and HPLC analysis were carried out for the evaluation of spoilage microorganisms, sensory quality and the presence of preservatives (potassium sorbate and sodium benzoate). Τhe prevalence of Campylobacter spp., Salmonella, and Listeria monocytogenes was 50%, 11% and 44%, respectively. In the case of Campylobacter, from a total of 40 isolates, 27 were identified as Campylobacter coli, 4 as Campylobacter jejuni, whereas the remaining 9 belonged to unidentified Campylobacter species. Pseudomonas spp. was the dominant spoilage microbial genus in 43% of the samples, while in 31% of them a co-dominance of Pseudomonas spp. and Brochothrix thermosphacta was observed. Total aerobic counts increased to 7.0 log CFU/g at the 1st, 2nd or 3rd day of storage in 71% of the samples, while sensory analysis showed that 80% of the samples were characterized as spoiled after 3, 4 or 5 days. The presence of preservatives was confirmed in 31% of the samples and slightly affected the microbiological profile. In conclusion, the obtained data demonstrated the occurrence of foodborne pathogens and allowed the acquisition of an overall view about the microbiological quality of marinated chicken products.
•Foodborne pathogens were detected in marinated chicken products of the Greek market.•Campylobacter coli was the most prevalent pathogenic microorganism.•High initial microbial load and short shelf life were observed in most products.•The flavor of marinades could mask the spoilage off-odors.
The advent of high-throughput sequencing technologies in recent years has revealed the unexpected presence of genus Photobacterium within the chicken meat spoilage ecosystem. This study was ...undertaken to decipher the occurrence, the growth patterns and the genotypic biodiversity of Photobacterium phosphoreum on chicken breast fillets stored aerobically at 4 °C through conventional microbiological methods and molecular techniques. Samples were periodically cultured on marine broth agar (MA; supplemented with meat extract and vancomycin) for the enumeration of presumptive bioluminescent Photobacterium spp. In total, 90 bioluminescent bacteria were recovered from the initial (time of first appearance), middle and end stages of storage. Concomitantly, 95 total psychrotrophic/psychrophilic bacteria were isolated from the same medium to assess the presence and diversity of non-luminous photobacteria. Genetic diversity between bioluminescent isolates was assessed with two PCR-based DNA fingerprinting methods, i.e. RAPD and rep-PCR. Moreover, the characterization of selected bacterial isolates at the genus and/or species level was performed by sequencing of the 16S rRNA and/or gyrB gene. Bioluminescent bacteria were scarcely encountered in fresh samples at population levels of ca. 2.0 log CFU/g, whilst total psychrotrophic/psychrophilic bacteria were found at levels of ca. 4.4 log CFU/g. As time proceeded and close to shelf-life end, bioluminescent bacteria were encountered at higher populations, and were found at levels of 5.3 and 7.0 log CFU/g in samples from the second and third batch, respectively. In the first batch their presence was occasional and at levels up to 3.9 log CFU/g. Accordingly, total psychrotrophic/psychrophilic bacteria exceeded 8.4 log CFU/g at the end of storage, suggesting the possible underestimation of bioluminescent populations following the specific cultivation conditions. Sequence analysis assigned bioluminescent isolates to Photobacterium phosphoreum, while genetic fingerprinting revealed high intra-species variability. Respectively, total psychrotrophs/psychrophiles were assigned to genera Pseudomonas, Shewanella, Psychrobacter, Acinetobacter, Vibrio and Photobacterium. Non-luminous photobacteria were not identified within the psychrotrophs/psychrophiles. Results of the present study reveal the intra- and inter-batch variability on the occurrence and growth responses of P. phosphoreum and highlight its potential role in the chicken meat spoilage consortium.
•Insights into genetic variability of bioluminescent photobacteria in refrigerated chicken breast fillets.•P. phosphoreum levels varied within and between batches in fresh and spoiled samples.•P. phosphoreum population was found at levels potentially connected with spoilage processes.•Non-luminous photobacteria were not detected in spoilage microbiota.
