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Quality deterioration of fish as the result of disintegration of proteins, even under chill storage, yields peptides and amino acids, which make the quality susceptible to further degradation as the result of bacterial conversion of these amino acids into hazardous biogenic amines (BAs). In this study, six biogenic amines (putrescine, cadaverine, spermidine, spermine, histamine and tyramine) in 16 days ice stored common carp (Cyprinus carpio) were evaluated at 5 intervals (0, 4, 8, 12 and 16 days). Higher levels of putrescine and cadaverine were detected at all intervals, indicating they can be good markers to determine the carp quality. Spermidine and spermine levels fluctuated during the storage and the levels of dangerous histamine and tyramine were too low to raise any concern.

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  The biogenic amines content of whole rainbow trout (Oncorhynchus mykiss) and its related bacterial load (psychrotroph and psychrophiles, pseudomonads and mesophiles) were monitored during ice storage in a period of eighteen days (zero, 3, 6, 9, 12, 15 and 18). The levels of putrescine, cadaverine and histamine and bacterial loads increased (P<0.05) during storage but tyramine was not detected in any of the samples. Initial concentration of putrescine was 0.4 and finally reached to 8.97 mg/g, and psychrotroph and psychrophiles were the dominant microorganisms. The best correlatios were found among putrescine and psychrotroph and psychrophile and its regression equation derived relating PUT, pse and psy (R=./98): [PUT =0.83 pse + 0.69psy+ 0.41[. In adition another regression equation derived relating CAD and time (R=0.955): [CAD =0.576 time - 3.49[.It is therefore concluded that although the quality control of Rainbow trout can be approximately estimated by measurement of either putrescine or psychrophiles with the usage of derived equation, but it's much better to evaluate some of these factors simultaneously to accomplish a precise quality assessment.

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Probiotics are non-pathogenic and beneficial bacteria that contribute to improving digestive health, preventing various types of cancer, and boosting the body's immune system, among other benefits. The aim of this study was to investigate the probiotic potential and antimicrobial activity of the strain Lacticaseibacillus rhamnosus JCM 1136. In this research, the probiotic and safety characteristics of the strain were assessed, including acid resistance at pH 2, 3, and 4, bile resistance (0%, 0.3%, 0.5%, and 0.7% bile salt concentration), hydropHobicity, potential for producing DNase enzyme and biogenic amines, hemolytic activity, antioxidant activity, cholesterol absorption capacity, and resistance to common antibiotics. The antimicrobial effect of the strain against pathogenic bacteria (Shigella dysenteriae, Salmonella typhimurium, Escherichia coli, Staphylococcus aureus, Listeria innocua, and Bacillus cereus) was evaluated using the agar well diffusion and disk diffusion methods. The results showed that L. rhamnosus JCM 1136 exhibited survival capability at different pH levels. The growth of the strain decreased with increasing bile salt concentration. L. rhamnosus JCM 1136 showed intermediate to the antibiotic Ampicillin and sensitivity to other antibiotics. The hydropHobicity, antioxidant activity by DPPH and ABTS methods, and cholesterol absorption capacity of the strain were 50.0 ± 50.53%, 50.0 ± 23.44%, 62.0 ± 50.48%, and 43.0 ± 55.41%, respectively. No production of DNase enzyme, biogenic amines, or hemolytic activity was observed in the strain. L. rhamnosus JCM 1136 exhibited a greater antimicrobial effect against Gram-positive bacteria. The results indicate that L. rhamnosus JCM 1136 possesses desirable probiotic characteristics and can be used in the production of probiotic food products.
 

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In this study, molecular identification of Lactiplantibacillus pentosus v390 was performed using 16S rRNA gene analysis with FYM27 and R1492 primers. The viability of the strain was assessed under acidic conditions at pH 5.2, 5.3, and 5.4, and resistance to bile at concentrations of 0%, 3.0%, 5.0%, and 7.0% was investigated. Antioxidant activity, cholesterol absorption, hydrophobicity, potential for DNase enzyme production, biogenic amines, hemolytic activity, and resistance to common therapeutic antibiotics were evaluated. The antimicrobial effect of the strain against pathogenic bacteria (Shigella dysenteriae, Salmonella enterica serovar Typhimurium, Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Bacillus subtilis) was examined using the well and disk diffusion method. The results showed that the L. pentosus v390 strain had the ability to survive at different pH levels, but after three hours of storage at pH 5.2, the bacterial count decreased. The strain demonstrated growth capability at various bile salt concentrations. L. pentosus v390 was intermediate to the antibiotic Nitrofurazone, resistant to Nalidixic and Imipenem antibiotics, and sensitive to Vancocin, Gentamicin, Chloramphenicol, Penicillin, and Ciprofloxacin antibiotics. The hydrophobicity, antioxidant activity (DPPH and ABTS), and cholesterol absorption of the strain were 38.0 ± 50.46%, 40.0 ± 20.37%, 45.0 ± 9.39%, and 47.0 ± 50.36%, respectively. No DNase enzyme production, biogenic amines, or hemolytic activity were observed from the strain. L. pentosus v390 exhibited stronger antimicrobial effects against Gram-positive bacteria. The results indicated that L. pentosus v390 has desirable probiotic properties that require further research to confirm its application potential in food product development.
 

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Background: With the growing tendency of people to consume organic dairy products, there is always a risk of pathogenic microbial strains in unhygienic locally prepared products. Local sheep yogurt as an organic product is one of the most valuable dairy products in Iran.
 Objectives: The aims of this study were molecular and phenotypic identification of lactic acid bacteria (LAB) isolated from sheep yogurt from Hamadan and investigation of their pathogenic characteristics.
Materials and Methods: The LAB isolated from yogurt samples were identified phenotypically and molecularly by PCR amplification of the 16S rDNA region and subsequent sequencing. The pathogenic and safety characteristics of the isolates including antibiotic resistance, blood hemolysis, amino acid decarboxylase, DNase, and gelatinase activities were then investigated.
Results: Forty-seven bacteria were isolated from yogurt samples, and only 22 gram-positive isolates reacted negatively to catalase. Based on the results, the isolates were molecularly characterized as 4 Lactobacillus helveticus, 5 Enterococcus mori, 2 Streptococcus salivarius subsp. thermophilus, 5 Lactobacillus kalixensis, and 6 Lactobacillus delbrueckii subsp. bulgaricus. Phenotypic identification also confirmed the isolates assigned to S. thermophilus and L. bulgaricus by molecular identification.
Conclusion: The evaluation of the pathogenic characteristics of the species associated with yogurt production, S. thermophilus and L. bulgaricus, confirmed that two isolates (HL1, HL2) of L. bulgaricus are safe as starter culture for yogurt production.