Antagonistic activities of lactic acid bacteria from fermented foods and beverage of Ladakh against Yersinia enterocolitica in refrigerated meat

In vitro characterization of lactic acid bacteria and bifidobacteria from wild and domestic pigs: probiotic potential for post-weaning piglets

BACKGROUND

Gastrointestinal diseases in weaned piglets are a frequent cause of high morbidity and mortality in domestic pigs. The use of antibiotics is problematic due to increasing antibiotic resistance in bacterial populations, for which reason the use of suitable probiotics is highly recommended to maintain animal health and welfare.

RESULTS

In this study, 57 strains of biologically safe lactic acid bacteria (LAB) and bifidobacteria originating from the gastrointestinal tract (GIT) of pigs were identified and characterized in terms of their probiotic properties for potential use in weaned piglets. These strains were divided into two sets based on their origin - from the GIT of wild boars (n = 41) and from the GIT of domestic pigs (n = 16). Strains obtained from wild boars exhibited greater taxonomic diversity compared to isolates from domestic pigs. While searching for coding sequences (CDS) encoding bacteriocins and bile salt hydrolases (BSH), no significant difference was detected between the two tested groups. On the other hand, CDS encoding adhesinlike factors were more frequent in the dataset isolated from wild boars than in the dataset obtained from domestic pigs. Moreover, more CDS encoding carbohydrateactive enzymes (CAZymes) were carried in the genomes of strains obtained from wild boars. Utilization of important selected carbohydrate substrates, such as starch, D-raffinose, D-mannose, Dcellobiose and gentiobiose, was confirmed by API testing. Antimicrobial activity against at least one of the five tested pathogens was found in 51% of wild boar strains but in none of the isolates from domestic pigs.

CONCLUSION

This suggests that the intestinal microbiota of wild boars could serve as a promising source of probiotics for domestic pigs.

Ultra-processed plant-based analogs: Addressing the challenging journey toward health and safety

Currently, plant-based analogs are presented as healthier alternatives to the products they are intended to replace. However, the processing to which ultra-processed plant-based analogs are subjected to acquire the characteristics of animal-derived products might result in the opposite effect, producing unhealthy ultra-processed foods. In the present review, a list of strategies widely known and already employed in animal-derived products is suggested to achieve healthier, safer, and tastier ultra-processed plant-based analogs: fermentation, employment of probiotics and postbiotics, NaCl replacement or substitution, addition of antioxidants, and fatty profile enhancement. In general, these strategies are not yet applied to the plant-based products available on the market; thus, this research paper might induce new investigation pathways for researchers and producers to develop actually healthier alternatives.

Application of lactic acid bacteria for the biopreservation of meat products: A systematic review

The increasing concern of consumers about food quality and safety and their rejection of chemical additives has promoted the breakthrough of the biopreservation field and the development of studies on the use of beneficial bacteria and their metabolites as potential natural antimicrobials for shelf life extension and enhanced food safety. Control of foodborne pathogens in meat and meat products represents a serious challenge for the food industry which can be addressed through the intelligent use of bio-compounds or biopreservatives. This article aims to systematically review the available knowledge about biological strategies based on the use of lactic acid bacteria to control the proliferation of undesirable microorganisms in different meat products. The outcome of the literature search evidenced the potential of several strains of lactic acid bacteria and their purified or semi-purified antimicrobial metabolites as biopreservatives in meat products for achieving longer shelf life or inhibiting spoilage and pathogenic bacteria, especially when combined with other technologies to achieve a synergistic effect.

Isolation of Antibacterial, Nitrosylmyoglobin Forming Lactic Acid Bacteria and Their Potential Use in Meat Processing

The use of nitrite as a colorant and preservative in meat processing is associated with health risks. This study aimed to isolate nitrite-substituting lactic acid bacteria for use as natural biological colorants and preservatives. Among the 106 strains isolated from fermented foods, two strains with excellent ability to convert myoglobin and metmyoglobin (Met-Mb) to red nitrosylmyoglobin (Mb-NO) were selected. The superior ability to form Mb-NO was confirmed through UV-visible spectrophotometry, Fourier transform infrared spectrometry, electron spin resonance analysis, nitric oxide synthase activity assay, and Met-Mb reductase activity assay. The potent antibacterial activity was confirmed through biofilm and cytomembrane breakage of the indicator bacteria. Though performing 16S rDNA sequencing, they were identified as two different strains of Lactobacillus plantarum. Based on their favorable characteristics, their applications in the meat industry were further evaluated. This study identified a novel dual-function natural biological colorant and preservative to substitute nitrite in meat products. The application of the two strains would decrease the hazardous of nitrite to health.

Meat Native Lactic Acid Bacteria Capable to Inhibit Salmonella sp. and Escherichia coli

In this study, lactic acid bacteria (LAB) strains were isolated from ground beef, and it was analyzed if they have any effect on the growth of two reference bacteria (Salmonella sp. and Escherichia coli). It was found that five isolates showed an inhibitory effect in both reference bacteria by spot at the lawn assay. These bacteria were selected to perform growth kinetics in co-culture to determine if they modify the growth parameters of the reference bacteria. Subsequently, LAB cultures and three treatments (crude extract, thermally treated and thermally treated with neutral pH) of cells free supernatants (CFS) were screened by the agar well diffusion assay. In co-culture, selected LAB altered the growth rate and reduce the maximum population of both reference bacteria. While, LAB cultures and CFS also showed antimicrobial activity, and there was no significant difference among CFS treatments. LAB isolated from ground beef showed an antimicrobial effect against the reference bacteria that could be used for meat biopreservation purposes.

Probiotic properties of a phytase producing Pediococcus acidilactici strain SMVDUDB2 isolated from traditional fermented cheese product, Kalarei

The nutritional challenge faced by the monogastric animals due to the chelation effects of phytic acid, fuel the research on bioprospecting of probiotics for phytase production. Pediococcus acidilactici SMVDUDB2 isolated from Kalarei, exhibited extracellular phytase activity of 5.583 U/mL after statistical optimization of fermentation conditions viz. peptone (1.27%); temperature (37 °C); pH (6.26) and maltose (1.43%). The phytase enzyme possessed optimum pH and temperature of 5.5 and 37 °C, respectively and was thermostable at 60 °C. The enzyme was purified 6.42 fold with a specific activity of 245.12 U/mg with hydrophobic interaction chromatography. The purified enzyme had K_m and V_max values of 0.385 mM and 4.965 μmol/min respectively, with sodium phytate as substrate. The strain depicted more than 80% survival rate at low pH (pH 2.0, 3.0), high bile salt concentration (0.3 and 0.5%), after gastrointestinal transit, highest hydrophobicity affinity with ethyl acetate (33.33 ± 0%), autoaggregation (77.68 ± 0.68%) as well as coaggregation (73.57 ± 0.47%) with Staphylococcus aureus (MTCC 3160). The strain exhibited antimicrobial activity against Bacillus subtilis (MTCC 121), Mycobacterium smegmatis (MTCC 994), Staphylococcus aureus (MTCC 3160), Proteus vulgaris (MTCC 426), Escherichia coli (MTCC 1652) and Lactobacillus rhamnosus (MTCC 1408). The amount of exopolysaccharide produced by the strain was 2 g/L. This strain having the capability of phytate degradation and possessing probiotic traits could find application in food and feed sectors.

Inhibitory Substances Produced by NativeLactobacillus plantarumUTNCys5-4 Control Microbial Population Growth in Meat

Microbial contamination is the cause of extensive economic loss in the food sector. Previously, the wide-range antimicrobial capacity of inhibitory substances secreted by theLactobacillus plantarumUTNCys5-4 strain was demonstratedin vitro; however, its mechanism of action in the food matrix remains unclear. This study was aimed to evaluate the effect of antimicrobials produced by the Cys5-4 strain in raw meat applied as pure cell cultures, cell-free supernatant (CFS), and partially purified peptides. The bacteriological results indicated the presence of commensal microbes exhibiting resistance to several antibiotics in meat samples purchased from the local market. Dipping solutions containing antimicrobial substances produced by Cys5-4 resulted in a decrease by 1.91,1.69, and 1.55 log10in cell counts upon addition of CFS, peptides and respectively pure cell culture in raw meat at day 9 of storage with refrigeration. The microbial population was maintained in the untreated meat samples during storage. An increase in pH and a concentration of released ammonia was detected in nontreated meat, indicating protein degradation. The Cys5-4 peptides exerted their bacteriolytic mode of action inducing damage in the cell membrane of the target bacteria, allowing the leaching of DNA/RNA content. The results indicate that coating meat with CFS containing Cys5-4 is a promising approach to protect against further contamination by microorganism spoilage, as well as an alternative for increasing the shelf life of raw meat.

Evaluation of Probiotic-Beverage Matrix Interaction for Efficient Control of Enterobacter aerogenes and Staphylococcus aureus

HIGHLIGHTS

L. rhamnosus GG in sea buckthorn matrix inhibited E. aerogenes and S. aureus. L. rhamnosus GG was more efficient in sea buckthorn than in apple matrix. Enhanced protection in sea buckthorn matrix may be due to higher phenolic content. WPC and the probiotic increased the pseudoplasticity of the juice matrices.

Control de crecimiento de Listeria monocytogenes en co- cultivo con Lactobacillus plantarum

Listeria monocytogenes (Lm) es un patógeno emergente causante de enfermedades transmitidas por alimentos de consumo masivo principalmente cárnicos y lácteos. Actualmente se buscan diferentes estrategias para su control, entre ellas compuestos naturales producidos por otros microorganismos como  ácidos orgánicos y otros compuestos como lactoferrina, lisozima y bacteriocinas, estas últimas producidas por especies de bacterias como Lactobacillus plantarum (Lp). El objetivo de esta investigación fue determinar el efecto de cepas de Lp aisladas de suero costeño sobre el control de crecimiento de L. monocytogenes inoculada en co-cultivos. Se realizaron curvas de crecimiento para Lm, Lp 60-1 y Lp 62-1 y co-cultivos de cada Lp con Lm.  La cinética de crecimiento fue evaluada determinando la viabilidad durante 24h en agares selectivos. La tasa de crecimiento de L. monocytogenes inoculada como control en leche UHT y en co-cultivos, presentaron diferencias significativas (p<0,05) entre los tratamientos, evidenciando que el control alcanzó un valor promedio de tasa de crecimiento mayor (μmax =0,65 h-1), que el obtenido para los co-cultivos  con Lp 60-1 y Lp 62-1 (μmax =0,22 h-1 y μmax =0,27 h-1 respectivamente). La mayor diferencia fue alcanzada en el co cultivo con Lp  60-1, obteniendo el menor valor promedio de tasa de crecimiento de Lm. Los resultados demuestran la eficiencia de las cepas de Lp (60-1 y 62-1) para el control de crecimiento de Lm en leche UHT comercial, siendo esta una alternativa  para reducir el uso de aditivos químicos durante la producción de lácteos.

Lighting the anaerobic digestion process in rural areas: obtainment of struvite from bovine manure digestate

The objective of this research was to obtain struvite from digested matter from a bio rural digester fed with bovine manure. To determine operating variables to recover struvite (PO43- and NH4+ ions), researchers developed an experiment design in which they evaluated the combined effect of the Mg2+: PO43- molar ratio (1.5:1; 2.5:1 and 3.5:1), reaction time (10, 50 and 90 min) and stirring speed (100, 450 and 800 rpm). The recovery rates obtained were 55±4.94 % and 58±7.72 % for NH4+ and PO43- respectively. The favorable conditions were 1.5 molar ratio, 50 minute reaction time and 450 rpm stirring speed. Struvite crystal formation and composition were confirmed using petrographic microscopy and infrared radiation. Struvite yield was 295.75 mg /l from digestate employed.

Differential Proteomic Analysis of Lactic Acid Bacteria-Escherichia coli O157:H7 Interaction and Its Contribution to Bioprotection Strategies in Meat

Human infection by Enterohemorrhagic Escherichia (E.) coli (EHEC) occurs through the ingestion of contaminated foods such as milk, vegetable products, water-based drinks, and particularly minced meats. Indeed EHEC is a pathogen that threatens public health and meat industry. The potential of different Lactic Acid Bacteria (LAB) strains to control EHEC in a meat-based medium was evaluated by using a simple and rapid method and by analyzing the growth kinetics of co-cultures (LAB-EHEC) in a meat-based medium. The activity of LAB toward EHEC in co-cultures showed variable inhibitory effect. Although, LAB were able to control EHEC, neither the produced acid nor bacteriocins were responsible of the inhibition. The bacteriocinogenic Enteroccus (Ent.) mundtii CRL35 presented one of the highest inhibition activities. A proteomic approach was used to evaluate bacterial interaction and antagonistic mechanisms between Ent. mundtii and EHEC. Physiological observations, such as growth kinetics, acidification ability and EHEC inhibitory potential were supported by the proteomic results, demonstrating significant differences in protein expression in LAB: (i) due to the presence of the pathogen and (ii) according to the growth phase analyzed. Most of the identified proteins belonged to carbohydrate/amino acid metabolism, energy production, transcription/translation, and cell division. These results contribute to the knowledge of competition strategies used by Ent. mundtii during its co-culture with EHEC setting new perspectives for the use of LAB to control this pathogen in meat.