Background: The identification of bacterial species in fermented PDO (protected designation of origin) cheese is important since they contribute significantly to the final organoleptic properties, the ripening process, the shelf life, the safety and the overall quality of cheese. Methods: Ten commercial PDO feta cheeses from two geographic regions of Greece, Epirus and Thessaly, were analyzed by 16S metagenomic analysis. Results: The biodiversity of all the tested feta cheese samples consisted of five phyla, 17 families, 38 genera and 59 bacterial species. The dominant phylum identified was Firmicutes (49% of the species), followed by Proteobacteria (39% of the species), Bacteroidetes (7% of the species), Actinobacteria (4% of the species) and Tenericutes (1% of the species). Streptococcaceae and Lactobacillaceae were the most abundant families, in which starter cultures of lactic acid bacteria (LAB) belonged, but also 21 nonstarter lactic acid bacteria (NSLAB) were identified. Both geographical areas showed a distinctive microbiota fingerprint, which was ultimately overlapped by the application of starter cultures. In the rare biosphere of the feta cheese, Zobellella taiwanensis and Vibrio diazotrophicus, two Gram-negative bacteria which were not previously reported in dairy samples, were identified. Conclusions: The application of high-throughput DNA sequencing may provide a detailed microbial profile of commercial feta cheese produced with pasteurized milk.

Lactic acid bacteria (LAB) play an important role as natural food preservatives. However, the characterization of the variety of their metabolites is limited. The objective of this study was to determine the production of specific metabolites of Lacticaseibacillus rhamnosus, Levilactobacillus brevis and Lactiplantibacillus plantarum by an optimized liquid chromatography with an ultraviolet/diode detection (HPLC-UV/DAD) method and to investigate their potential antimicrobial activity against specific food pathogens. Based on the results of this study, the main metabolites detected in Levilactobacillus brevis were 103.4 μg mL−1 DL-p-Hydroxyphenyllactic acid (OH-PLA) and 2.59 μg mL−1 vanillic acid, while 216.2 μg mL−1 OH-PLA, 19.0 μg mL−1 salicylic acid, 3.7 μg mL−1 vanillic acid, 6.9 μg mL−1 ferulic acid, 4.2 μg mL−1 benzoic acid and 1.4 μg mL−1 4-Hydrocinnamic acid were identified in the Lactiplantibacillus plantarum strain and 147.6 μg mL−1 OH-PLA and 4.9 μg mL−1 ferulic acid were identified in Lacticaseibacillus rhamnosus. This study provides alternative approaches for the molecules involved in the antimicrobial activity of food microorganism fermentation. These molecules may be used as antimicrobial ingredients in the food industry instead of conventional chemical preservatives.

Lactic acid bacteria (LAB) play an important role as natural food preservatives. However, the characterization of the variety of their metabolites is limited. The aim of this study was to determine specific metabolites produced by Lactobacillus gasseri ATCC 33323 by an optimized liquid chromatography with an ultraviolet/diode detection (HPLC-UV/DAD) method and to investigate their potential antimicrobial activity against specific food pathogens (Salmonella enterica ATCC14028; Staphylococcus aureus ATCC 29213; Escherichia coli ATCC 25922 and Klebsiella pneumoniae ATCC 700603). At the same time, the possible antioxidant activity of metabolites of L. gasseri was tested using the free radical DDPH• (a, a-Diphenyl-β-Picrylhydrazyl). Based on the results of this study, the major metabolites detected in L. gasseri were 6.0 ppm OH-PLA, 3.73 ppm 1,2-dihydroxybenzene, 2.31 ppm benzoic acid in 5 days. This study provides a different alternative approach to the others involved in the antimicrobial activity of food fermented by microorganisms. These molecules can be used as antimicrobial ingredients in the food industry instead of conventional chemical preservative.

The research focused to detect and identify genetic polymorphisms in exon 7 of the β-casein CSN2 gene in blood samples from Greek Holstein cows. For this purpose, DNA was extracted from 120 blood samples of cows. The desired region of exon 7 was amplified by PCR, resulting in a 121 bp product. The PCR product was digested by restriction fragment length polymorphism (RFLP) method. The results suggest that the A1A2 genotype prevails over the others. Specifically, of the 120 cattle, 72 showed triple bands of 121 bp, 86 bp, and 35 bp indicating the A1A2 genotype. The 42 cattle showed a single band at 121 bp, indicating that they carried the A1A1 genotype. The remaining 6 showed only two bands of 86 and 35 bps, indicating that they carried the A2A2 genotype. In the total population of heterozygotes A1A2-0.60 were the most frequent, while homozygotes A2A2-0.06 were the least frequent ones. This suggests a slight superiority of allele A-0.65.

This e research focused on the detection and identification of genetic polymorphisms in exon 7 of the β-casein CSN2 gene in blood samples from Greek Holstein cows and from local breeds of cattle, such as Vrachykeratiki, Katerinis, and Sykias. For this purpose, DNA was isolated from 780 blood samples obtained from Greek Holstein cows, 86 from three local breeds of cattle, namely Brachyceros, Katerinis, and Sykias, and 14 from Greek buffalo. The desired region of exon 7 was amplified by PCR, resulting in 121 and 251 bp products in bovine and buffalo samples. The PCR product was digested with restriction fragment length polymorphism (RFLP) on agarose gels. The restriction enzymes DdeI and TaqI were used. All of the blood samples had the amplified size. The results showed that 74.4% of the Greek Holstein cows had the A2A2 β-casein genotype, the three native breads Vrachykeratiki had 57.7%, and the other two had 100% of the A2A2 β-casein. From the 14 Greek buffalo, 100% had the A2A2 β-casein.