Safety aspects of Lactobacillus plantarum strains isolated from Siahmazgi cheese

Abstract

In order to use lactic acid bacteria as starter and non-starter cultures in fermentative products, their safety qualities should be evaluated. The objective of the present study was to evaluate safety characteristics including antibiotic sensitivity pattern, antimicrobial effect, H2O2 production, and biogenic amine production by Lactobacillus plantarum strains isolated from Siahmazgi cheese. Lactobacillus plantarum strains were unable to produce tyramine except for SD6 strain. All strains in the current study were able to produce histamine but unable to decarboxylate neither lysine nor ornithine. Lactobacillus plantarum strains showed considerable antimicrobial activity against Salmonella typhimurium and Listeria monocytogenes. All L. plantarum strains showed stronger antimicrobial activity against S. typhimurium (3.5-42.55 mm) than L. monocytogenes (1.5-30.49 mm). The SC9 strain had the strongest inhibitory effect against both pathogens. After titering pH of the medium to approximately 6.5, no antimicrobial activity was noticed indicating that the antimicrobial activity of L. plantarum strains was contributed to their acid production and not to bacteriocin. All L. plantarum strains were capable of producing H2O2. SA32 and SD13 strains with 2.37 and 0.77 mmol/L were the strongest and the weakest strains regarding H2O2 production, respectively (P˂ 0.05). All L. plantarum strains were sensitive to chloramphenicol, erythromycin, rifampicin, and tetracycline, yet resistant against vancomycin, and norfloxacin. Four patterns of antibiotic resistance were observed among L. plantarum strains. Only two strains of SC9 and SE4 were resistant against four antibiotics. L. plantarum strains naturally found in Siahmazgi cheese do not generally possess dangerous characteristics to be used in fermentative dairy products.

Brazilian artisanal cheeses are rich and diverse sources of nonstarter lactic acid bacteria regarding technological, biopreservative, and safety properties—Insights through multivariate analysis

“…This antagonistic effect was not very related to the production of bacteriocins because only 27 out of the 220 strains showed positive results in the production of compounds with proteinaceous nature. Thus, these findings are in agreement with those reported by other authors, who also attested that after neutralizing the pH of LAB supernatant, there was an absence or reduction in the inhibitory activity against indicator pathogens (Pisano et al, 2014;dos Santos et al, 2015;Sornplang and Piyadeatsoontorn, 2016;Ołdak et al, 2017;Partovi et al, 2019). Such behavior can be explained by other mechanisms of inhibition related to LAB in addition to bacteriocin production, such as competition for substrates and decreased pH levels by organic acid production (e.g., lactic, formic, propionic, and acetic acids; Favaro et al, 2015;Ołdak et al, 2019).…”

Technological and probiotic potential of autochthonous lactic acid bacteria from spontaneously fermented dromedary milk

“…(2020) reported lower ΔpH (6 hr) for Lactococcus lactis strains isolated from spontaneously fermented cow milk, which did not exceed 0.6 pH units. The variability in the acidifying capacity between the isolated LAB could be attributed to variations in the metabolic activities of the strains (Partovi, Gandomi, & Akhondzadeh Basti, 2018). LAB strains with rapid acidification potential could be used as starter cultures in the elaboration of fermented foods since lower pH values are desired for organoleptic properties as well as for the prevention from the growth of spoilage microorganisms.…”