Activity Of Cell-free Supernatant Research Articles

Antibacterial Activity of Cell-Free Supernatants of Probiotic Lactobacillus against Bacterial Pathogens Associated with Vaginal Infections

Vaginal infections are common female disease conditions that account for the prevalence of gynecological disorders which facilitate the increasing antimicrobial resistance and failure of prevalent treatment choices. In this study, the antibacterial activity of cell free supernatants (CFS) of probiotic Lactobacillus obtained from ogi (fermented maize) was evaluated against bacterial pathogens associated with vaginal infections. Bacterial pathogens isolated from high vaginal (n=22) and endocervical swabs (n=18) were bio-typed and assayed for hemolytic activity, biofilm production, antibacterial susceptibility pattern, and the CFS antagonistic activity. The occurrence of the vaginal bacterial pathogens was 33.0% for Streptococcus spp. and 31.0% for Staphylococcus aureus, with more than 70% resistance rates to amoxicillin, cefotaxime, imipenem/cilastatin, nalidixic acid, nitrofurantoin, cefuroxime, ceftriaxone sulbactam, ampiclox, cefixime and levofloxacin. More than 30% of the isolates produced biofilms. Of the four identified probiotic strains, only CFS from L. plantarum and L. acidophilus exhibited observable antagonistic reaction, with L. plantarum showing higher antibacterial activity against Staphylococcus condimenti, and L. acidophilus against Klebsiella pneumoniae. With the results of this study revealing the antibacterial activity of probiotic Lactobacillus CFS against vaginal bacterial pathogens, probiotic Lactobacillus can be suggested for use as prophylactic and bioprotective agents in the therapeutic management of vaginal bacterial infections and preservation of the vaginal microbiota.

The combined effect of Weisella cibaria and Fusarium oxysporum nanoparticles on cervical cancer cells

The predicted global cancer burden is expected to surpass 20 million new cancer cases by 2025. Despite recent advancements in tumor therapy, successful cancer treatment remains challenging. The emerging field of nanotechnology offers great opportunities for diagnosis, imaging, as well as treatment of cancer. The biosynthesis of silver nanoparticles by fungi is an ecologically clean and nontoxic method compared to other physical and chemical methods. The purpose of this study is to determine the Synergistic Effect of Combination Nanoparticles Synthesized from Fusarium oxysporum with Weisella cibaria against cervical cancer cells. The study has done from 2022 to March 2023 in the food microbiology laboratory in the Department of Biology / College of Science / Mustansiriyah University. Lactic acid bacteria (LAB) were isolated from food sources (Turnip, Cabbage, Cauliflower), after serial steps from treated NaCl , then cultured in MRS (Man-Rogosa-Sharpe) broth, finally examined under a microscope. The antibacterial activity of Cell Free Supernatant (CFS) s that was produced by these isolates was detected to choose the best one and diagnosed by PCR and DNA sequencing. The nanoparticles (AgNo3) that were produced from Fusarium oxysporum by biosynthesis were obtained from higher studies laboratory for fungi, and these fungi was submitted to toxicity test. The Synergist effect of chosen LAB and Fusarium oxysporum nanoparticles was studied against cervical cancer cells. Results show that all food sources were rich in LAB and the best antibacterial activity was to turnip source and according to molecular diagnosis was Weisella cibaria , that recorded in NCBI as (MG7865551). The synergistic effect of W. cibaria and nanoparticles showed and decrease the cancer line viability rate after 72 hr. exposure to this effect.

Bioactive compound and chemical characterization of lactic acid bacteria from fermented food as bio-preservative agents to control food-borne pathogens

Context: Lactic acid bacteria (LAB), which are found in many fermented foods, are known to produce antimicrobial compounds that play a vital role in food bio-preservation. Aims: To screen, identify, characterize, and determine the secondary metabolites of LAB isolated from Thai fermented foods that are beneficial against Escherichia coli and Staphylococcus aureus. Methods: The antimicrobial activity of cell free supernatant (CFS) was evaluated by agar well diffusion assay, and determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC). Bacterial strains were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), and chemical compound was conducted by gas chromatography and mass spectrometry (GC-MS). Additionally, microbial dynamic and bile salt tolerance were assessed. Results: Seven of the 90 lactic acid isolates from Thai fermented foods, showed antibacterial activity against E. coli and S. aureus in the 12.00–16.00 mm inhibitory zone. It was identified that the bacteria were Lactobacillus pentosus, Lactobacillus farciminis, Lactobacillus brevis, and Lactobacillus plantarum. The best antibacterial activity was represented by LBST1861 strain, which also provided bile salt resistance at 0.3% for 24 hours and had MIC and MBC values of 12.5 mg/mL and 50.0 mg/mL against S. aureus and E. coli, respectively. Furthermore, the GC-MS discovered a total of 16 chemical compounds that may be used to limit microbial growth and has a potential to be employed as a bio-preservative. Conclusions: The most potent strain of LBST1861 strain against S. aureus and E. coli as L. plantarum, isolated from fermented foods in Thailand, generated significant bioactive chemicals that can be applied to promote food products.

Antimicrobial activity of cell free supernatants from probiotics inhibits against pathogenic bacteria isolated from fresh boar semen

The use of antibiotics with semen extender appears to be a practical solution to minimise bacterial growth in fresh boar semen preservation. Unfortunately, the excessive use of antibiotics promotes antimicrobial resistance (AMR). This becomes a worldwide concern due to the antimicrobial resistance genes transmitted to animals, environment, and humans. Probiotics are one of the alternative methods to reduce antibiotic use. They could inhibit pathogenic bacteria by producing antimicrobial substances in cell free supernatants (CFS). Nevertheless, there is no comprehensive study undertaken on inhibitory activity against pathogenic bacteria isolated from boar semen origin. Our study investigated the efficacy of CFS produced from selected probiotics: Bacillus spp., Enterococcus spp., Weissella spp., Lactobacillus spp., and Pediococcus spp. inhibiting pathogenic bacteria isolated from fresh boar semen. Besides, the semen-origin pathogenic bacteria are subjected to identification, antimicrobial resistance genes detection, and antibiotic susceptibility test (AST). Pseudomonas aeruginosa, Escherichia coli, and Proteus mirabilis are the most common pathogens identified in boar semen with resistance to numerous antibiotics used in pig industry. The CFS with its antimicrobial peptides and/or bacteriocin constituent derived from selected probiotics could inhibit the growth of pathogenic bacteria carrying antimicrobial resistance genes (mcr-3 and int1 genes). The inhibition zones for Pseudomonas aeruginosa, Escherichia coli, and Proteus mirabilis provided more efficient results in the CFS derived from Lactobacillus spp. and Pediococcus spp. than those of the CFS produced from Enterococcus spp., Weissella spp. and Bacillus spp., respectively. It is worth noted that as the incubation time increased, the antibacterial activity decreased conversely. Our results on CFS with its antimicrobial peptides and/or bacteriocin constituent inhibits semen-origin pathogenic bacteria guide the direction as a promising alternative method used in the semen extender preservation of the pig industry.

Antibacterial and Antibiofilm Activity of the Mixed Lactobacilli Against the Most Bacterial Etiology of Otitis Media

The present study aimed to investigate the anti-biofilm activity of Cell Free Supernatant (CFS) and Biosurfactant (BS) of mixed lactobacilli (L. acidophilus and L. plantarum) against biofilm formation by bacterial pathogens isolated from chronic otitis media. In addition, the antimicrobial potential of ciprofloxacin in combination with CFS of lactobacilli species was evaluated againt the tested pathogens. The automated identification of bacterial isolates was peroformed by VITEK2 compact system their antibiotics susceptibility was evaluated using disc diffusion method. The minimum inhibitory concentrations (MIC) of the mixed lactobacilli CFS and ciprofloxacin were determine against the bacterial isolates using broth micro-dilution assay. Anti-biofilm activities of CFS and bio-surfactant of the mixed lactobacilli were evaluated against the biofilm–associated bacterial isolates. The minimum biofilm inhibitory concentrations (MBIC50) were determined. In the current study, one hundred sixty-two ear swab were collected from had otitis media cases with chronic discharging. These patients attended to the ENT department in the medical consultation clinic at Baquba Teaching Hospital and to private doctors’ clinics. Ear swabs were taken from both genders during September 2021 to the end of December. The most bacterial species isolated from otitis media samples were Pseudomonas aeruginosa and Staphylococcus aureus. Ciprofloxacin was an effective antibiotic against the tested pathogenic bacteria. The mixed lactobacilli CFS showed an inhibitory effect at MIC90 (25%) against P. mirabilis but (50%) against P. aeruginosa, S.aureus, and K. pneumoniae. The data illustrated that CFS of mixed lactobacilli was synergized ciprofloxacin against otitis media-bacterial isolates. The CFS of mixed lactobacilli exhibited a higher MBIC50 against K. pneumoniae (50%) compared to other bacterial isolates. In addition, a higher MBIC50 of the mixed lactobacilli bio-surfactant was reported against P. aeruginosa 50%, compred to the other bacterial species. The authors concluded that tested probiotics cells, the mixed lactobacilli, and their products possessed an effective antimicrobial potential and enhanced ciprofloxacin activity to control the chronic otitis media-associated bacteria and inhibit their persistent biofilm formation.

Evaluation of Rye Bran Enzymatic Hydrolysate Effect on Gene Expression and Bacteriocinogenic Activity of Lactic Acid Bacteria

Lactic acid bacteria (LAB) bacteriocins can be considered as a bio-preservatives and an alternative to antibiotics, but the high manufacturing costs limit their commercial application. The screening of LAB strains for bacteriocinogenic activity was carried out and the effect of rye bran enzymatic hydrolysate (RBEH) on gene expression and bacteriocin production was evaluated. qPCR and RT-PCR was applied for bacteriocin gene detection and their expression quantification. The agar diffusion technique with the test strains of Bacillus spp., Staphylococcus spp. and Salmonella enterica was performed for antimicrobial activity assessment of LAB cultivated in MRS broth and RBEH (processed with proteases and cellulases). The genes of different bacteriocins were revealed for thirteen out of eighteen LAB strains, while the antimicrobial activity was detected only for four of them. The strains of Lactobacillus paracasei VKPM B-11657 and L. salivarius VKPM B-2214 with unnamed class IIb bacteriocin gene demonstrated the widest spectrum of activity. The growth patterns and bacteriocin gene expression differed between both strains and media. The activity of cell-free supernatants after cultivation in RBEH was slightly lower. However, the test strain of S. epidermidis was inhibited by L. paracasei cultivated in RBEH but not in MRS. Thus, rye bran can be applied as a sole source of nutrients for LAB fermentation and bacteriocin production.

Anti-Biofilm Activity of Cell Free Supernatants of Selected Lactic Acid Bacteria against Listeria monocytogenes Isolated from Avocado and Cucumber Fruits, and from an Avocado Processing Plant.

Listeria monocytogenes forms biofilms on food contact surfaces, a niche from where it dislodges to contaminate food products including fresh produce. Probiotics and their derivatives are considered promising alternative strategies to curb the presence of L. monocytogenes in varied food applications. Nonetheless, studies on their anti-biofilm effects against L. monocytogenes from avocados and cucumbers are sparse. This study screened the biofilm formation capabilities of L. monocytogenes strains Avo and Cuc isolated from the avocado and cucumber fruits respectively, and strain 243 isolated from an avocado processing plant; and evaluated the anti-biofilm effects of cell free supernatants (CFS) of Lactobacillus acidophilus La14 150B, Lactiplantibacillus plantarum B411 and Lacticaseibacillus rhamnosus ATCC 53103 against their biofilms formed on polyvinyl chloride (PVC) and stainless steel. All the L. monocytogenes strains formed biofilms (classified either as moderate or strong biofilm formers) on these materials. The presence of CFS reduced the biofilm formation capabilities of these strains and disrupted the integrity of their pre-formed biofilms. Quantitative reverse transcriptase polymerase chain reaction revealed significant reduction of positive regulatory factor A (prfA) gene expression by L. monocytogenes biofilm cells in the presence of CFS (p < 0.05). Thus, these CFS have potential as food grade sanitizers for control of L. monocytogenes biofilms in the avocado and cucumber processing facilities.

Characterization and Selection of Potential Antifungal Lactic Acid Bacteria Isolated From Turkish Spontaneous Sourdough.

The aim of this research was to investigate the antifungal potential of lactic acid bacteria (LAB) isolated from Turkish spontaneous sourdough collected in summer and winter seasons from 25 different small bakeries in Trabzon, Giresun, Ordu, and Samsun. Lactic acid bacteria (933 isolates) were screened for inhibition of three common food spoilage molds (Aspergillus flavus, Aspergillus niger, and Penicillium expansum). Eight LAB isolates identified as Weissella cibaria 908, Lactiplantibacillus plantarum subsp. plantarum 2114, Leuconostoc pseudomesenteroides 2619, L. plantarum subsp. plantarum 2702, Fructilactobacillus sanfranciscensis 2709, Levilactobacillus brevis 2216Y, L. pentosus Y118, and L. plantarum subsp. plantarum Y201 by 16 S rRNA sequencing, which were found to have high antifungal activity against all the test molds. The antifungal activity of cell free supernatants from LAB isolates was not altered after thermal treatment and proteolytic enzyme proteinase K. The cell free supernatants obtained from LAB showed a high antifungal effect against molds with inhibition zone diameter up to 20mm at pH 3.0, but no inhibitory activity was determined after pH neutralization. Moreover, all cell free suspension samples were able to maintain their efficacy up to a 1:4 dilution. The antifungal activity of supernatants was mostly related to organic acid content, especially lactic acid ranged from 4.33 to 8.41g/L. The results indicated that eight bacterial isolates obtained from spontaneous Turkish sourdough could constitute biopreservative cultures, which may be used in food industry.

Biofilm Formation and Antibacterial Properties of Lactobacillus Isolated from Indigenous Dairy Products

Background: The health benefits of probiotic bacteria are not unknown to anyone. On the other hand, indigenous dairy sources are a potential source of native probiotics. This study aimed to describe the inhibitory activity of Cell-Free Supernatant (CFS), planktonic cells, and biofilm form of Lactobacillus strains isolated from native dairy sources on food pathogens.&#x0D; Methods: Antibacterial activities of the CFS of Lactobacillus strains were assessed by the microplate method and via violet staining, and in planktonic cells, and biofilm forms were performed by the spread plate method.&#x0D; Results: The results showed that despite the large differences in biofilm formation power among the strains, most of them can produce biofilm. Lactobacillus delbrueckii subsp. bulgaricus, Lactobacillus plantarum, Lactobacillus delbrueckii subsp. Lactis, Lactobacillus brevis, and Lactobacillus lactis subsp. lactis formed the strongest biofilm, respectively. Planktonic states reduce the pathogens bacterial by about 1.43 log, but in biofilm forms, decreased Listeria monocytogenes by about 4.8 log compared to the control, and in the case of Pseudomonas aeruginosa, a growth reduction of about 2.8 logs was observed.&#x0D; Conclusion: According to the study, biofilm produced by probiotic strains can be considered a new approach for biological control. Also, indigenous dairy sources can be considered by researchers to extract natural and beneficial probiotics.

Correlation between the Antimicrobial Activity and Metabolic Profiles of Cell Free Supernatants and Membrane Vesicles Produced by Lactobacillus reuteri DSM 17938.

The aim of the work is to assess the antimicrobial activities of Cell Free Supernatants (CFS) and Membrane Vesicles (MVs), produced by Lactobacillus reuteri DSM 17938, versus Gram-positive and Gram-negative bacteria and investigate their metabolic profiles. The Minimum Inhibitory Concentration was determined through the broth microdilution method and cell proliferation assay while the Minimum Bactericidal Concentration was determined by Colony Forming Units counts. The characteristics of the antimicrobial compounds were evaluated by pH adjustments, proteinase treatment, and size fractionation of the CFS. The cytotoxicity of CFS was tested on two human cell lines. A detailed snapshot of the L. reuteri metabolism was attained through an untargeted metabolic profiling by means of high resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) coupled with Electrospray Ionization Source (ESI). The results showed (i) a greater efficacy of CFS and its fractions towards Gram-negative compared to Gram-positive bacteria; (ii) an antimicrobial effect related to pH-dependent compounds but not to MVs; (iii) a molecular weight < 3 KDa as well as an a non-proteinaceous nature of the antimicrobial compounds; and (iv) more than 200 and 500 putative metabolites annotated in MVs and supernatants, covering several classes of metabolites, including amino acids, lipids, fatty and organic acids, polyalcohols, nucleotides, and vitamins. Some putative compounds were proposed not only as characteristic of specific fractions, but also possibly involved in antimicrobial activity.

Biochemical and molecular characterization of lactase producing bacterium isolated from dairy effluent

In the present study, the microbial source for potent lactase producers was explored to supplement the lactase intolerant individuals. Dairy effluent was screened for lactase producing bacteria by conventional microbiological methods. Among the positive isolates, one isolate VUVD001 was found to be a strong producer of lactase enzyme and this strain identified by 16S rDNA analysis. The lactase producing bacterium is identified as Bacillus subtilis by biochemical and 16S rDNA analysis. The VUVD001 strain found to survive in a temperature range of 20–55 °C, pH range of 5–8 and a salt concentration up to 8%. Further, the partially purified enzyme preparation was tested by zymogram analysis for activity testing using x-gal and the enzyme activity of cell free supernatant was estimated to be 15.10 U/ml at 37 °C, 4% NaCl and pH of 7.0. Our finding reports a new isolate Bacillus subtilis VUVD001 strain which can be used as potential strain for commercial production of lactase.

Preliminary characterization and inhibitory activity of bacteriocin like substances from Lactobacillus casei against multi-drug resistant bacteria

Antimicrobial resistance is a mounting threat to the control of infectious diseases worldwide. Due to the increasing rate of drug resistance, there is continuous requirement for new and safe antimicrobial agents both for therapeutic purposes and food industries. The potential of bacteriocin has attracted much attention in recent years.We characterized bacteriocin like substances produced by Lactobacillus casei. This bacterium produces bacteriocin like substances that have the ability to inhibit multi-drug resistant pathogenic bacteria such as Staphylococcus aureus, Klebsiella pneumoniae, and Proteus vulgaris. To investigate the antimicrobial property of the bacteriocin like substances produced by L.casei, cell free supernatant (CFS) was prepared and antagonistic activity of cell free supernatant was determined by agar well diffusion method. Production of bacteriocin like substances was greatly affected by nutrient media, pH, temperature and incubation period. Highest inhibitory activity was observed when L.casei was grown in MRS broth (De Man, Rogosa and Sharpe broth) (pH 4.0) for 72 hoursat 37°C. The active components of CFS responsible for antagonistic activity are proteinaceous in nature since they are susceptible to heat treatment. Partial purification of this CFS was done by organic solvent extraction method. Among the eight isolates tested, only S. auereus, Proteus vulgaris and K. pneumoniae showed more sensitivity to the partially purified crude bacteriocin like substances (CBLS) than CFS.&#x0D; Bangladesh J Microbiol, Volume 36 Number 1 June 2019, pp 01-06

Identification of lactic acid bacteria as antimicrobial from milk Toraja Belang buffalo

Lactic acid bacteria can produce antimicrobial compound. The bacteria can be found in milk. The objective of this research is to study antibacterial activity and identification of lactic acid bacteria from milk of Toraja Belang Buffalo South Sulawesi. The lactic acid bacteria were isolated by pour plate method using MRSA containing 1 % CaCO3. Antimicrobial activity of the isolates against Salmonella typhi, Staphylococcus aureus and EPEC were assayed using agar well diffusion method. The result showed that among 14 isolates of LAB, the most potent antibacterial activity of Cell Free Supernatant against to EPEC is K1B, Staphylococcus aureusis K4A2 and Salmonella typhi is K5B2. Based on the 16S rDNA sequence, K1B, K4A2 and K5B2 isolates were identified as Enterococcus faecalis ATCC19433T with similarity 99.758 %, 100% and 99.759% respectively.

Antibacterial Activity of Lactobacillus (LB) Strains Isolated from Goat Milk against ESBL Producing E. coli Causing Wound Infections

Lactobacillus (LB) species are well known probiotics with beneficial effects to human health. Their antimicrobial activity is one of the most important probiotic characteristics. Wound infections are the most frequent bacterial infections encountered in community settings. Extended spectrum β-lactamases (ESBLs) are enzymes produced by pathogenic bacteria that enable such pathogenic bacteria as multi drug resistant. Treatment of infections by these drug resistant bacteria require newer anti microbialsthat are highly expensive and possibility of many side effects. Microbial products consideredas the best source for therapeutic agents worldwide. Lactobacillus species were isolated from 2 days fermented goat Milk. Theantimicrobial activity of cell-free supernatant and partially purified bacteriocin was determined by well diffusion method and equal mixed culture method. All isolated ESBL were processed and identified as per the CLSI guide lines. The organism was identified by GN ID and AST 280 of Vitec-II campact system and AES (Advance extended spectrum) tests. The current study showed that ESBL E. coli resistant to Cefazoline (96.6%), Ceftazidime (43.3%), Ceftriaxone (3.3%), Ciprofloxacin (76.6%), Meropenem (0%), Tobramycin (43.3%), Cefotaxime (93.3%), Ceftazidime + cluvalonic acid (3.3%), Cefotaxime + cluvalonic acid (3.3%), Cefperodoxime (96.6%), Piperacillin + Tazobactam (0%), Ampicillin (100%). Lactobacillus species exhibited an antibacterial effect on a narrow range of ESBL strains. However invitro effect is better than large number broad-spectrum antibiotics such: third-generation cephalosporins

Correlation between Biofilm Production and Bacterial Urinary Tract Infections: New Therapeutic Approach

BIOFILMS production during bacterial urinary tract infections (UTIs), being responsible for persistence and relapses. Bacterial producing biofilms are difficult to be eradicated as they reveled antibiotics resistant phenotype that correlated to provided protections by biofilms. The present study revealed that the gram negative bacteria (G-ve) were the most common uropathogenic bacteria causing UTIs with 64.28% biofilm producing ability especially Escherichia coli and Klebsiella pneumoniae. While, gram positive bacteria (G+ve) represented 23.63% of UTIs with 57.69% biofilm producing ability. The isolated uropathogenic bacteria demonstrated a high and widespread resistance (50% to 95 %) to all used antibiotics except Nitrofurantoin and Imipenem. The most antibiotics resistant uropathogenic isolates were biofilm producers and some of them revealed haemolytic activity. The present study indicated the importance of studying biofilm producing ability of uropahogenic bacteria as it represented 62.72% during UTIs. The anti-biofilm activity of cell free supernatant of Lactobacillus plantarum subsp. plantarum DSMZ 20174 and Lactobacillus acidophilus DSMZ 20079T against biofilms of both G-ve and G+ve uropathogenic bacteria beside their acid and bile salt tolerance gave potentiality for their use during UTIs as a beneficial tool for dissociation or prevention of biofilms and enable antimicrobial drugs from eradication of infections.

Bio-efficiency of Antifungal Lactic Acid Bacterial Isolates for Pomegranate Fruit Rot Management

Out of 360 lactic acid bacteria (LAB) from leaves, flowers, buds and fruits of pomegranate, 224 were antagonistic towards Aspergillus flavus. In all, 81.6% of antifungal LAB were cocci and 18.3% were rod shaped. Majority (39.7%) of them was obtained from flowers and 27 isolates showed strong antifungal activity. Antifungal isolates were identified by Gram positive card kit and 16S rRNA gene sequencing as Enterococcus faecium, E. durans, Lactococcus lactis spp. cremoris, L. lactis spp. lactis, Leuconostoc mesenteroides, Lactobacillus brevis and Pediococcus pentosaceus. All the isolates showed maximum antifungal activity at pH 6.5 and 30 °C on MRS agar. The antifungal activity of cell free supernatants from the entire isolates was same under static and shaking conditions except PFL9 that showed decreased production under shaking conditions. The isolates, PFL4, PFL9, PB6, PB119, PL14, PFR61 and PFR77 showed broad antifungal activity. PFL9 and PFR77 had the longest survival on fruits and there was no significant reduction (P > 0.05) in their population till 8th day post inoculation as determined under field conditions. Cell formulations of PFL9 and PFR77, and Dithane (fungicide preparation) delayed the development of rot caused by Alternaria alternata, Phomopsis varsoniana and Corynespora cassiicola with equivalent potential (P > 0.05). Thus, pomegranate is the source of diverse antifungal LAB which can be used as an effectual biocontrol agent in the management of fungal fruit rot of pomegranate.

Antimicrobial effect of selected lactic acid bacteria against microorganisms with decarboxylase activity

The main purpose of this study was to evaluate the antimicrobial activity of twenty-one bacteriocinogenic lactic acid bacteria (12 strains of Lactococcus lactis subsp. lactis, 4 strains of Lactobacillus gasseri, 3 strains of Lb. helveticus and 2 strains of Lb. acidophilus, LAB) against 28 Staphylococcus and 33 Enterococcus strains able to produce tyramine, putrescine, 2-phenylethylamine and cadaverine. The antimicrobial activity of cell-free supernatants (CFS) from tested LAB was examined by an agar-well diffusion assay. Nine out of twenty-one strains (33%) showed the inhibitory effect on tested enterococci and staphylococci, namely 9 strains of Lactococcus lactis subsp. lactis. The diameters of inhibition zones ranged between 7 mm and 14 mm. The biggest diameter of 14 mm inhibition was obtained with the CFS's from strains CCDM 670 and CCDM 731 on Enterococcus sp. E16 and E28. The cell-free supernatants from Lactococcus lactis subsp. lactis CCDM 71 and from Lactococcus lactis subsp. lactis CCDM 731 displayed the broadest antibacterial activity (52% inhibition of all tested strains). On the other hand, the cell-free supernatants from the screened Lactobacillus strains did not show any inhibitory effect on the tested Staphylococcus and Enterococcus strains. Nowadays, the great attention is given to the antibacterial substances produced by lactic acid bacteria. With the ability to produce a variety of metabolites displaying inhibitory effect, the LAB have great potential in biopreservation of food.

Biopreservation potential of lactic acid bacteria from Andean fermented food of vegetal origin

Microbial fermentations have long represented a way of natural biopreservation of raw materials, which frequently originated new food products. Among them, traditionally fermented products still manufactured by native populations all around the world are source of lactic acid bacteria (LAB) strains with high biotechnological potential. LAB are food grade microorganisms and therefore a good alternative to chemicals to be applied in food preservation. A total of 130 LAB isolates recovered from “chicha” and “tocosh”, traditional fermented Andean products of vegetal origin, were screened for antimicrobial activities against spoiler fungi Meyerozyma guilliermondii CECT 1021 (synonym Pichia guilliermondii), Penicillium roqueforti CECT 2905NT, Aspergillus oryzae CECT 2094NT and Aspergillus niger CECT 2807 as well as against foodborne pathogens Escherichia coli O157:H7 CECT 5947, Listeria innocua CECT 910T and Salmonella enterica subsp. enterica serovar Typhi CECT 4138. LAB isolates represented nine species and four genera that exhibited a general inhibition of food pathogens and were also active against A. oryzae and M. guilliermondii while a poor inhibition of A. niger and P. roqueforti was produced. Antifungal activity of cell free supernatants (CFS) from seven selected strains grown in MRS was confirmed against toxigenic fungi Aspergillus parasiticus CECT 2681, Penicillium expansum CECT 2278 and Fusarium verticilloides CECT 2987 and also on the three foodborne bacteria included in the study. Phenyllactic and 3,5-Di-O-caffeoylquinic acids were identified as the predominant bioactive compounds in CFS by QuEChERS extraction with LC-MS-LIT detection approach. Four out of seven strains free of antibiotic resistances involving L. plantarum M5MA1 and M9MM1 from chicha and L. fermentum T3M3 and Lc. mesenteroides T1M3 from tocosh showed high potential to be used as biopreservatives in food applications.

Antimicrobial Activity of Cell Free Supernatant of Lactic Acid Bacteria Isolated from Fermented Durian Flesh against Multiple Antibiotic Resistance’s Salmonella Associated with Food Poisoning Cases in Malaysia

Epidemic of food poisoning cases and outbreaks associated with Salmonella spp. have been increased all over the world. Most of food poisoning cases in Malaysia related to Salmonella are associated with contaminated water compared to other sources. Finding alternative treatment to reduce foodborne cases becomes crucial, and bio-preservation using lactic acid bacteria (LAB) is one of strategy that can be used in food industries. The objective of this study was to determine the antimicrobial activities in vitro of cell free supernatant from eight LAB strains isolated from fermented durian flesh, which were 5 strains from Lactobacillus buchneri, 1 strain from each culture, Lactobacillus plantarum, Lactobacillus brevis 1 and Lactobacillus acidophilus 1 against 23 species of various serotypes of pathogenic Salmonella obtained from food poisoning cases in Malaysia. The antimicrobial activity of crude bacteriocins from cell free supernatant (CFS) of LAB strains were tested using well diffusion method. Susceptibility test of eight selected Salmonella strains was done using disk diffusion method (DDT) against twelve selected antibiotics. Results showed that crude bacteriocins of Lb. plantarum, Lb. buchneri, Lb. brevis 1 and Lb. acidophilus 1 from fermented durian flesh had strong inhibitory effect against most of 23 species of MAR's Salmonella associated with food poisoning cases with intermediate to high inhibitory zone by average mean from 16 mm to 22 mm diameter zone. All eight Salmonella strains were resistant to bacitracin, nalidixic acid and vancomycin and some strains were also resistant to ampicillin, penicillin, streptomycin and tetracycline. Further study could be utilised to understand the mechanism of selected LAB bacteriocin producer from fermented durian flesh as antimicrobial substance.

Novel Antibacterial Activity of Lactococcus Lactis Subspecies Lactis Z11 Isolated from Zabady

The purpose of this study was to select and characterize a probiotic bacterium with distinctive antimicrobial activities. In this respect, Lactococcus lactis subspecies lactis Z11 (L. lactis Z11) isolated from Zabady (Arabian yoghurt) inhibited other strains of lactic acid bacteria and some food-born pathogens including Listeria monocytogenes, Bacillus cereus and staphylococcus aureus. The inhibitory activity of cell free supernatant (CFS) of L. lactis Z11 isolated from zabady was lost by proteolytic enzymes, heat resistant. Consequently, the active substance(s) of CFS was characterized as a bacteriocin. This bacteriocin has been shown to consist of protein but has no lipidic or glucidic moieties in its active molecule. Its activity was stable in the pH range 2.0 to 7.0 and was not affected by organic solvents. The L. lactis Z11 bacteriocin was produced in CFS throughout the mide to the late exponential phase of growth of the producer organism and maximum bacteriocin production was obtained at initial pH 6.5 at incubation temperature of about 30°C.