Screening Of Lactic Acid Bacteria Research Articles

Screening of lactic acid bacteria for antagonism toward pathogens and biofilm-forming activity

Screening of lactic acid bacteria for antagonism toward pathogens and biofilm-forming activity

Screening of lactic acid bacteria with immune modulating property, and the production of lactic acid bacteria mediated fermented soymilk

Background: Lactic acid bacteria (LAB) are reported to have immune activating property. The genetically modified LAB strains producing interleukin (IL) -10 were under consideration for the treatment of inflammatory bowel diseases (IBD). Soybean is rich in necessary nutrients, and the fermented soybean products are known for its health benefits. Aims and Objectives: The current study was aimed to screen LAB with the immune activating property, and production and evaluation of LAB mediated fermented soymilk product. Materials and Methods: Screening of LAB from the fermented foods collected in Chiang Mai. To select a potent LAB strain, the LAB isolates were scrutinized for acid tolerant, bile tolerant, growth rate, antimicrobial ability, adhesion property, and induction of IL-10 production. The physical properties of fermented soymilk (FSM) were evaluated, and in vitro activation of IL-10 by FSM was assessed using Caco-2 cell line. Results: About 742 LAB, strains were isolated from 335 fermented food samples. Based on the tested properties, LAB33 was selected as a potent LAB strain, and used for the fermentation of soymilk for 30 days. The LAB33 FSM was superior in quality regarding probiotic nature and microbiological safety. Conclusion: The results of the study suggested that LAB33 is the potent probiotic strain for the production of soymilk-based fermented functional food supplements for the betterment of IBD patients. Further, strain identification is required to register the strain in a public repository, and sustainable utilization for the benefit of mankind.

Lactic acid bacteria of the <i>Leuconostoc</i> genus with high innate immunity-stimulating activity

We screened lactic acid bacteria that exhibited high innate immunity-stimulating activity by monitoring muscle contraction activity in silkworms. Heat-treated fractions of lactic acid bacteria, Leuconostoc carnosum #7-2, Leuconostoc gelidum #4-2, and Leuconostoc mesenteroides 8/11-3, had high (250-460 units/mg) innate immunity-stimulating activity. These lactic acid bacteria proliferated in milk to concentrations of 1 × 106 colony forming unit/mL. The present findings suggest that the silkworm muscle contraction assay is useful for screening lactic acid bacteria with high innate immunity-stimulating activity, and that the assay can be used for the production of fermented foods made from milk.

Applicability of a colorimetric method for evaluation of lactic acid bacteria with probiotic properties

Rapid colorimetric methods using various indicator reagents have been developed to monitor bacterial viability. Here, we examined the applicability of a method based on the reduction of resazurin or water-soluble tetrazolium salt-8 (WST-8) to screen lactic acid bacteria (LAB) for growth, tolerance against bile acid and low pH. The resazurin reduction test proved unsuitable for screening LAB such as Lactobacillus plantarum and Leuconostoc mesenteroides since it reacted with acid present in the cultures. LAB growth could be indirectly quantified by measuring WST-8 reduction. This method proved more sensitive and quickly results than counting bacterial colony forming units and turbidity at 600 nm in the presence of bile and acid. Our results suggested that the WST-8-based method could be useful for the characterization of growth and tolerance of the lactic acid producing bacteria.

In vitro screening of lactic acid bacteria isolated from gastrointestinal tract of Atlantic Salmon (Salmo salar) as probiont candidates

A total of 20 lactic acid bacteria (LAB) were isolated from the gastrointestinal tracts of Atlantic salmon (Salmo salar) and screened for antimicrobial activity against six fish pathogens using either a microtiter plate assay or a well diffusion assay. The results indicated that three LAB exhibited antimicrobial activity against at least two pathogens. Based on their partial 16S ribosomal deoxyribonucleic acid (16S rDNA) sequences, these isolates were identified as Lactobacillus farraginis, Pediococcus acidilactici, and P. pentosaceus. In addition, these LAB were able to tolerate the simulated gastrointestinal tract conditions (stomach and intestine), had a good adhesion capacity to intestinal mucus as well as were able to grow in intestinal mucus of Atlantic salmon. These results suggest that these LAB are potential probionts in aquaculture. However, further studies are required to evaluate probiotic properties in aquatic animals.

Isolation and screening lactic acid bacteria for riboflavin production and their use for bioenrichment of curd

As many as 47 lactic acid bacteria were isolated from various vegetables and fruits and raita collected from local households and characterized. All of them were Gram positive and catalase negative. The isolates were screened for riboflavin production. The riboflavin production varied from 0.86 to 10.90 mg L-1. The isolate Ra1 produced the highest riboflavin (10.90 ppm). Incidentally, it also produced 5.6 per cent lactic acid and 21.4 ppm exopolysaccharide (EPS). Similarly, N2 and F2 isolates produced 10.90 and 10.20 ppm riboflavin and 21.17 and 21.24 ppm EPS, respectively. These three selected isolates were used for preparing a functional curd andevaluated. The curd produced by inoculating N2 and Ra1 were of very good quality with excellent flavor, taste and texture and smooth cutting quality. Ra1 produced a functional curd with the highest riboflavin content (13.97 ppm). N2 and RA1 resulted in very high acceptability index of 95.37 and 94.44 per cent, respectively. The betterorganoleptic parameters of the functional curd may also be due to high lactic acid and exopolysaccharide production by these isolates. Thus, by inoculating riboflavin synthesizing LAB isolates to curd, riboflavin-enriched functional curd with enhanced consumer appeal, can be produced.

SCREENING OF SOME FERMENTED MILK FOR DECARBOXYLASE AND BIOGENIC AMINES PRODUCING MICROORGANISMS AND THEIR PUBLIC HEALTH SIGNIFICANCE

The objectives of this study were based on screening for presence of decarboxylase producing microorganisms (Enterobacteriaceae, Enterococci and Lactobacilli) in sour milk, yoghurt and labenh, collected from supermarkets in Ismailia City. The isolated strains were tested for decarboxylase activity and the levels of histamine, tyramine, putrescine and cadaverine were determined in the examined samples. The results revealed that all the examined samples were contaminated with EnterobacteriaceaeandEnterococci at variable counts. All the isolated strains of Enterobacteriaceae, Enterococci and Lactobacillus spp. have the potential to release decarboxylase enzymes with biogenic amines formation. The examined samples were found to contain the estimated amines with variable levels, expect yoghurt that didn't contain tyramine. In conclusion, there was a positive correlation between the type of microorganisms present in fermented milk and the type of biogenic amines formed. The prevention of biogenic amines formation in fermented milks could be achieved by following good hygienic measures and careful screening of lactic acid bacteria for amino acid decarboxylase activity before selecting as starter or probiotic strains in dairy industry.

PHENOTYPIC CHARACTERIZATION AND MOLECULAR IDENTIFICATION OF SOME LACTIC ACID PRODUCING BACTERIA IN RAW MILK OF DIFFERENT ANIMAL SPECIES

A total number of 228 apparently healthy milk samples were collected from individual and bulk tank milk of cows (100 and 86 samples, respectively), goats (30) and she camel (12) for isolation of some lactic acid bacteria (LAB) especially that have coccal form. The preliminary screening LAB community at the genus level depending on the basis of morphological characteristics showed that, the isolates were differentiated into 4 groups; Enterococci, Leuconostocs, Pediococci and Streptococci with a total percentage of 61%. The highest % of LAB was recorded for Enterococcus species in the different animal species especially in camel milk (41.7%). Antibacterial activity of selected 75 LAB strains against S. aureus, S. uberis, E. coli and Yersinia enterocolotica as bovine mastitis pathogens were detected. 53 out of 75 of the selected strains showed antibacterial effect against the tested pathogens. Eighteen Enterococcus isolates have inhibitory effects on all of the tested bacteria with inhibition zone diameter ranged between 10-25 mm. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was used as an aid step for identification of LAB strains. Thus the SDS-PAGE results confirmed the biochemical identification of the isolated cultures for Leuconostoc mesenteroides with a percentage of similarity (90.8%), for Pediococcus acidilactici (92.5%), for Enterococcus hirae (99.84%) and for Streptococcus thermophilus (99.89%). Representative strains of genus Enterococci that had higher antibacterial activity against mastitis pathogens were subjected to sequence-based identification. The obtained sequences of these isolates were submitted to the Gen Bank database with accession numbers KU847974 and KU847975 for E. faecium and E. hirae, respectively and showed 99% 16S rRNA sequence homology. It was concluded that raw animal milk may be a po­tential source for the isolation of probiotic LAB with antibacterial properties against mastitis pathogens that may be presented as an interesting alternative to antibiotic drugs to overcome the antibiotic resistance of mastitis pathogens as well as antibiotic residues in milk.

Partial Characterization of Bacteriocin Produced by Halotolerant Pediococcus acidilactici Strain QC38 Isolated from Traditional Cotija Cheese.

During a screening of lactic acid bacteria producing bacteriocin from Cotija cheese, the strain QC38 was isolated. Based on the 16S rRNA gene nucleotide sequencing (516 pb accession no KJ210322) and phylogenetic analysis, the isolate was identified as Pediococcus acidilactici. Neutralized cell-free supernatant was tested for antimicrobial activity against 17 Gram-negative and Gram-positive pathogens. Growth inhibition was achieved against Listeria monocytogenes (supplier or indication or source), Staphylococcus aureus, Vibrio vulnificus, Vibrio cholerae O1 Ogawa, Vibrio cholerae NO 01 and Salmonella enterica subsp. Enterica serovar Typhimurium. Bacteriocin-like substance, after heating at 121°C for 15 min it remained stable and its antimicrobial activity was observed at pH ranging from 1.0 to 10.0 but inactivated by α-chymotrypsin and proteinase K. Strain QC38 was able to grow in 1-9% NaCl concentration. The plate overlay assay showed an approximate size of bacteriocin-like substance between 3.4 and 6.5 kDa. P. acidilactici QC38 harboured a plasmid that contains a gene for a pediocin (PA-1).

The screening of lactic acid bacteria with antioxidant properties

Lactic acid bacteria (LAB) have been given special attention due to their probiotic functions and also the possible antioxidant effects. The 378 strains of LAB isolated from the wide range of samples were studied. In this study large part of the strains was obtained from plant surfaces (phylloplane) from locations at different climatic zones expecting variable antioxidative properties due to the difference in solar irradiation intensity. The total antioxidative activity as well as polyphenolic- and thiol-producing ability of screened isolates were tested. Polyphenolic and thiol content were strain- and media-dependent. The new simple modification of screening for potential antioxidant properties estimation has been developed. For the first time the link between solar irradiation and hydrogen peroxide sensitivity of isolated strains has been shown.

Antimicrobial activity and the presence of virulence factors and bacteriocin structural genes in Enterococcus faecium CM33 isolated from ewe colostrum.

Screening of lactic acid bacteria (LAB) isolated from ewe colostrum led to the identification and isolation of Enterococcus faecium CM33 with interesting features like high survival rates under acidic or bile salts condition, high tolerance for the simulated gastrointestinal condition, and high adhesive potential to Caco-2 cells. According the inhibition of pathogen adhesion test results, this strain can reduce more than 50% adhesion capacity of Escherichia coli, Shigella flexneri, Klebsiella pneumoniae, Listeria monocytogenes, and Staphylococcus aureus to Caco-2 cells. Based on the antibiotic sensitivity test findings, E. faecium CM33 was susceptible to gentamycin, vancomycin, erythromycin, ampicillin, penicillin, tetracycline, and rifampicin, but resistant to chloramphenicol, clindamycin, and kanamycin. Upon assessment of the virulence determinants for E. faecium CM33, this strain was negative for all tested virulence genes. Furthermore, the genome of this strain was evaluated for the incidence of the known enterocin genes by specific PCR amplification and discovered the genes encoding enterocins A, 31, X, and Q. Based on this study findings, the strain E. faecium CM33 can be considered as a valuable nutraceutical and can be introduced as a new potential probiotic.

In vitro and in situ screening of lactic acid bacteria and propionibacteria antifungal activities against bakery product spoilage molds

In the agri-food context, bioprotective cultures represent an interesting alternative to chemical preservatives. The aim of this study was to evaluate the in vitro and in situ antifungal activity of lactic acid bacteria (LAB) and propionibacteria against bakery product spoilage fungi. Firstly, the biodiversity of fungal contaminant in pound cakes and milk bread rolls, as well as the resistance to chemical preservatives of representative isolates (n = 21), were studied. Aspergillus and Eurotium species were the most dominant spoilage fungi and the most resistant towards the tested chemical preservatives. They were followed by Penicillium, Cladosporium and Wallemia spp. Secondly, an in vitro screening showed that the most active isolates against selected fungal targets belonged to the Leuconostoc spp., Lactobacillus reuteri and Lactobacillus buchneri groups among the 270 tested LAB, as well as to the Propionibacterium freudenreichi and Propionibacterium acidipropionici species for the 50 tested propionibacteria. Finally, in situ tests showed that cultures of isolates belonging to the Leuconostoc citreum, Lactobacillus sakei, Lactobacillus plantarum, Lactobacillus spicheri, L. reuteri and Lactobacillus brevis species could delay one or several target fungal growths after bakery product surface spraying. Moreover, different strain cultures led to delayed fungal growths after incorporation in milk bread rolls preparation. The combination of in vitro and in situ approaches allowed for the identification of bacteria exhibiting antifungal activity, providing future prospects for use as bioprotective cultures in bakery products.

Screening of Lactic Acid Bacteria as Potential Probiotics in Beef Cattle

Screening of Lactic Acid Bacteria as Potential Probiotics in Beef Cattle

Screening for lactic acid bacteria based on antihyperglycaemic and probiotic potential and application in synbiotic set yoghurt

Twenty lactic acid bacteria were screened for the abilities of rat intestinal α-glucosidase inhibition, short-chain fatty acids production, utilization of prebiotics as well as gastrointestinal tract tolerance. Nine strains inhibited α-glucosidase, four of which, Lactobacillus acidophilus CCFM6, Lactobacillus plantarum CCFM47, CCFM232 and Lactobacillus rhamnosus GG (LGG) were tolerant to simulated gastrointestinal juices with survival rates up to 60% following simulated digestion. When grown on soybean oligosaccharides (SBOs), CCFM47 produced propionic (39.9 mM) and butyric (3.5 mM) acids while strain CCFM6 produced 17.2 mM propionic acid. Strains CCFM6 and CCFM47 were further tested for their viability and survival in set yoghurt supplemented with SBOs. SBOs enriched yoghurt improved probiotic survival in the simulated gastric juice and significantly improved α-glucosidase inhibition (P < 0.05). Thus strains CCFM47 and CCFM6 can be used as probiotics with antihyperglycaemic potential in the formulation of functional foods such as yoghurt.

Screening of lactic acid bacteria that can form mixed-species biofilm with Saccharomyces cerevisiae.

The abilities of lactic acid bacteria (LAB) to form mixed-species biofilm with Saccharomyces cerevisiae in a static co-culture were investigated out of 168 LAB stock cultures, and two Lactobacillus plantarum strains (D71 and E31) and one Leuconostoc mesenteroides strain K01 were found to form mixed-species biofilm with S. cerevisiae BY4741. SEM observation showed that there was no significant difference in morphological properties among these three mixed-species biofilms and they resembled that formed by S. cerevisiae with L. plantarum ML11-11 previously isolated from a brewing sample of Fukuyama pot vinegar. The co-aggregation assays showed that L. plantarum D71 and L. plantarum E31 could co-aggregate with S. cerevisiae similarly to L. plantarum ML11-11, while L. mesenteroides K01 had no ability to co-aggregate with yeast. The above results indicate that aggregation followed by direct cell-to-cell contact is required for mixed-species biofilm formation between these L. plantarum strains and S. cerevisiae, though some different mechanism may be involved in biofilm formation between L. mesenteroides strain and S. cerevisiae.

Screening lactic acid bacteria with high yielding-acid capacity from pickled tea for their potential uses of inoculating to ferment tea products.

For there were very short of excellent strains inoculated to ferment tea products, the lactic acid bacteria from pickled tea were isolated, characterized and identified, and the acid production capacity of part better strains was determined. There are only 22 strains isolated from pickled tea, and 2 of them were yeast, and 8 strains selected from the other 20 strains all were identified as Lactobacillus plantarum. A1, L2 and L5 of L. plantarum with a high acid production capacity were screened out and could obviously shorten the fermentation time of pickled tea by the verification, which suggests that they have a potential use of inoculating to ferment tea products. It was the first report on screening lactic acid bacteria with high yielding-acid capacity from pickled tea, which will bring benefits to fermenting tea products by artificial inoculation.

Screening of lactic acid bacteria with potential protective effects against cadmium toxicity

Cadmium (Cd) is a toxic heavy metal that causes adverse health effects in humans and animals. In the present study, 33 strains of lactic acid bacteria (LAB) were screened for their potential probiotic capacity against Cd toxicity. The Cd binding ability was investigated first, and 10 strains with comparatively higher Cd binding properties were selected for further study through the evaluation of Cd tolerance, antioxidative capacity and acid and bile salt tolerance. The results revealed that as a reference strain, Lactobacillus rhamnosus GG had good Cd tolerance, antioxidative capacity and acid and bile tolerance, but the Cd binding ability of this strain was poor. Another strain, Lactobacillus plantarum CCFM8610, showed significantly better binding ability and Cd tolerance than the other tested strains. This strain also exhibited relatively good antioxidative properties and resistance to the simulated gastrointestinal conditions. This study suggests that L. plantarum CCFM8610 could be used as a potential probiotic in food applications against Cd toxicity.

In vitro screening of lactic acid bacteria for multi-strain probiotics

The aim of this research was to screen and evaluate some probiotic properties of lactic acid bacteria strains isolated from 150 animal fecal samples, such as cows, pigs, chickens, and ducks. To achieve an objective, 81 isolates were tested for antimicrobial activity, tolerance to bile salts and acid, potential adhesion to cell surface, and in vitro adhesion. The results of the antimicrobial activity against pathogenic bacteria showed that, out of 81 isolates, 61, 59, 43, 78, and 79 isolates had antimicrobial activity against Escherichia coli, Staphylococcus aureus, Salmonella sp., Shigella sp., and Kiebsiella sp., respectively. Most lactic acid bacteria (LAB) isolates were tolerant to 1.0% bile salts and were able to survive at pH 3.5 for 3h. Twelve isolates were then evaluated on their hydrophobic character. Five isolates with probiotic properties were subsequently selected. Sequence analysis of 16S rDNA demonstrated that 2 isolates belong to Lactobacillus reuteri (strains P8 and P30), 2 to Lactobacillus plantarum (strains P6 and P31), and another one to Lactobacillus paraplantarum (strain P25). To assess their viability in broiler chicken diets, 3 strains, L. plantarum (strain P6), L. paraplantarum (strain P25), and L. reuteri (strain P30), containing 108cfu/g were inoculated into a commercial chicken diet in the form of single strain and multi-strain preparations. We found that in all of the treatments, the numbers of viable cells of LAB (cfu/g of diet) were decreased below 107cfu/g after 3d of incubation. Therefore, based on our study, the single- and multi-strains may have a potential use as novel probiotics in broiler chicken diets.

Xylan-mediated aggregation of Lactobacillus brevis and its relationship with the surface properties and mucin-mediated aggregation of the bacteria.

Some Lactobacillus brevis strains were found to aggregate upon the addition of xylan after screening for lactic acid bacteria that interact with plant materials. The S-layer proteins of cell surface varied among the strains. The strains that displayed xylan-mediated aggregation retained its ability even after the removal of S-layer proteins. L. brevis had negative zeta potentials. A correlation between the strength of aggregation and zeta potential was not observed. However, partial removal of S-layer proteins resulted in decreases in the electric potential and aggregation ability of some strains. Therefore, xylan-mediated aggregation of L. brevis was considered to be caused by an electrostatic effect between the cells and xylan. L. brevis also aggregated in the presence of mucin, and the strengths of aggregation among the strains were similar to that induced by xylan. Thus, xylan- and mucin-mediated L. brevis aggregation was supposed to be caused by a similar mechanism.

Screening of Lactic Acid Bacteria from the Gut of Chrysichthys nigrodigitatus for Use as Probiotics in Aquaculture Production

Screening of Lactic Acid Bacteria from the Gut of Chrysichthys nigrodigitatus for Use as Probiotics in Aquaculture Production