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Characterization and profiling of bacteriocin-like substances produced by lactic acid bacteria from cheese samples.

ABSTRACT: Bacteriocins have become biological weapons against harmful food pathogens and have attracted interest as tools for biopreservation. The aim of this study was to isolate, identify and characterize lactic acid bacterial (LAB) strains from cheese samples, partially purify potential bacteriocins and characterize their antimicrobial activity against pathogens. Bacteriocin-producing organisms were screened by Agar spot assay test. Initially, 25 LAB isolates were isolated from the cheese samples and identified as Lactobacillius spp., among them five strains were able to produce bacteriocin whose antimicrobial activates were analysed by agar-well-diffusion assay test against pathogenic organisms. Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Streptococcus thermophillus and Listeria monocytogens were inhibited, while Enterococcus faecalis, Salmonella typhi, Escherichia coli and Pseudomonas aeruginosa were resistant to the antimicrobial substances from LAB isolates. For optimal production of bacteriocin, LAB broth cultures were harvested at exponential phase. The molecular weights of the bacteriocins are between 7.0-15.0 kDa. The bacteriocins were characterized on the basis of their sensitivity to heat, pH, enzymes, NaCl and treatments with organic solvents. These results revealed that the bacteriocins from Lactobacillius spp. isolated from the cheese might have potential antimicrobial properties and give new insight in the development of bio-preservative agents to prevent and control pathogenic bacterial infection.

SUBMITTER: Afrin S

PROVIDER: S-EPMC8374546 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The multifunctional properties of autochthonous lactic acid bacteria can be of use for enhancing the sensorial properties of food, as well as in food preservation. An initial screening for antimicrobial, proteolytic, and lipolytic capacities was done in 214 presumptive lactic acid bacteria isolates obtained from Chihuahua cheese manufacturing and during a ripening period of nine months. The antimicrobial screening was done by spot-on-the-lawn tests, using Listeria monocytogenes and Escherichia coli as indicator microorganisms; proteolysis was tested in casein-peptone agar and lipolysis in Mann-Rogosa-Sharpe (MRS)-tributyrin agar. More than 90% of the isolates hydrolyzed the casein, but only 30% hydrolyzed tributyrin; the inhibition of L. monocytogenes in the spot-on-the-lawn assay was used to select 39 isolates that had a bigger inhibition zone (>11.15 mm ± 0.3) than the control (Nisin producer Lactococcus lactis BS-10 Chr Hansen). The selected isolates were grown in MRS to obtain the neutralized cell-free supernatants and verify their antimicrobial activity by agar diffusion and the percentage of growth inhibition techniques. The selected isolates were also growth in casein peptone broth, and the cell-free supernatants were used for the determination of antioxidant activity by the radical scavenging of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2-azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS) techniques. The results were analyzed to identify similarities by cluster analysis, based on their antimicrobial and antioxidant capacities. The isolates were arranged into six clusters; one cluster that included 12 isolates demonstrated L. monocytogenes (784-2811 mm2/mL AU by agar diffusion assay) and E. coli (41%-47% growth inhibition) antimicrobial activity. The isolates clustered in these groups also showed competitive inhibition of both radicals (11%-19% of DPPH and 50%-60% of ABTS). The isolates from cluster one were also identified by 16S rDNA amplification and were identified as Enterococcus faecium. Traditional products such as Chihuahua cheese can be a source or lactic acid bacteria with metabolic properties that can be used in food preparation and preservation.

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Characterization and profiling of bacteriocin-like substances produced by lactic acid bacteria from cheese samples.

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