Characterization of lactic acid bacteria from Turkish Pastirma

Genotypic diversity and antagonistic activities of enterococci isolated from pastırma

The biodiversity of enterococci from pastırma (a traditional Turkish dry-cured meat product) by genotypic identification and the antagonistic activities of strains were investigated. Pastırma samples taken from 20 different small-scale factories were subjected to microbiological and physicochemical analysis. A hundred enterococci isolates were identified by 16S rRNA gene sequence analysis. To determine antagonistic activity of strains, Listeria monocytogenes and Staphylococcus aureus were used. The lactic acid bacteria and Micrococcus/Staphylococcus counts were ≥ 6 log cfu/g in 55% of the samples and 75% of the samples, respectively. Enterobacteriaceae was generally below the detectable level (< 2 log cfu/g). The enterococci count was higher than 6 log cfu/g in 30-35% of the samples, depending on the medium used. The enterococci isolates (100 isolates) were identified as E. faecium (80 strains), E. faecalis (19 strains) and E. hirae (1 strain) in genotypic identification. The nine E. faecium strains showed antagonistic activity against L. monocytogenes in the well diffusion test. In contrast, in the same antagonistic activity test, all of the strains had no antagonistic activity against S. aureus. Further studies could be planned to characterize E. faecium strains that show antagonistic activity against L. monocytogenes.

Impact of lactic acid bacteria strains against Listeria monocytogenes biofilms on various food-contact surfaces

Listeria monocytogenes is one of the most important foodborne pathogens, causing listeriosis, a disease characterized by high mortality rates. This microorganism, commonly found in food production environments and transmitted to humans by consuming contaminated food, has the ability to form biofilms by attaching to a wide variety of surfaces. Traditional hygiene and sanitation procedures are not effective enough to completely remove L. monocytogenes biofilms from food-contact surfaces, which makes them a persistent threat to food safety. Alternative approaches to combating Listeria biofilms are needed, and the use of lactic acid bacteria (LAB) and their antimicrobial compounds shows promise. The present study investigated the effect of Lactobacillus strains, previously isolated from various foods and known to possess antimicrobial properties, on the biofilm formation of L. monocytogenes on three different food-contact surfaces. To study L. monocytogenes IVb ATCC 19115 type, culture was preferred to represent serotype IVb, which is responsible for the vast majority of listeriosis cases. The results demonstrated that cell-free supernatants (CFSs) of LAB strains inhibited biofilm formation by up to 51.57% on polystyrene, 60.96% on stainless steel, and 30.99% on glass surfaces. Moreover, these CFSs were effective in eradicating mature biofilms, with reductions of up to 78.86% on polystyrene, 73.12% on stainless steel, and 72.63% on glass surfaces. The strong inhibition rates of one strain of L. curvatus (P3X) and two strains of L. sakei (8.P1, 28.P2) used in the present study imply that they may provide an alternate technique for managing Listeria biofilms in food production environments.

Effect of resistant starch types as a prebiotic

Since the role of intestinal microbiota in metabolism was understood, the importance of dietary components such as fibres and prebiotics, which affect the modulation of microbiota, has been increasing day by day. While all prebiotic components are considered dietary fibre, not every dietary fibre is considered a prebiotic. While fructooligosaccharides, galactooligosaccharides, inulin, and galactans are considered prebiotics, other fermentable carbohydrates are considered candidate prebiotic components based on in vitro and preclinical studies. Resistant starch, one of such carbohydrates, is considered a potential prebiotic component when it is made resistant to digestion naturally or chemically. In this review, both in vitro and in vivo studies in which the prebiotic capacity of type II, type III, and type IV resistant starch isolated from food and produced commercially was assessed were analyzed. According to the results of current studies, certain types of resistant starch are thought to have a high prebiotic capacity, and they may be candidate prebiotic components although positive results have not been achieved in all studies. KEY POINTS: • Resistant starch is undigested in the small intestine and is fermented in the large intestine. • Resistant starch fermentation positively affects the growth of Bifidobacterium and Lactobacillus. • Resistant starch can be considered a prebiotic ingredient.

In vitro evaluation of probiotic potential of Enterococcus faecium strains isolated from Turkish pastırma

This study is aimed at evaluating the probiotic potential of three Enterococcus faecium strains (called 29-P2, 168-P6 and 277-S3) isolated from 'pastırma', a Turkish traditional dry-cured meat product. For this, key probiotic properties and some functional characteristics of strains were tested in vitro. Antimicrobial activity of 3 E. faecium strains was evaluated against 18 indicator microorganisms consisting of 13 foodborne pathogens and 5 lactic acid bacteria and all strains were found as the producer of antimicrobial substance. Especially one strain 168-P6 showed a remarkable activity spectrum and inhibited all of the used foodborne pathogen indicators. Antimicrobial compounds produced by strains were identified by determining the effect of enzyme, pH and temperature on antimicrobial activity. All strains exhibited tolerance to acidic conditions and a simulated gastric environment. Also, strains exhibited high adhesion capacity. The safety of the strains was assessed by determining hemolytic activity and the resistance to 14 different antibiotics. None of the three strains exhibited hemolytic activity, also strains were found reliable in terms of clinically relevant antibiotics, only one strain 29-P2 was found resistant to vancomycin. In addition, metabolic activities of strains including lactic acid, hydrogen peroxide, exopolysaccharide production and proteolytic activity were determined and amounts of all metabolic products were found low. When evaluated all data obtained, it is believed that the strains have enviable characteristics as a probiotic candidate.