Evaluation of antimicrobial and cytotoxic activities of commercial Lactobacillus acidophilus against foodborne pathogens and the MCF-7 cell line

Lactic acid bacteria (LAB) are distinguished by their ability to produce lactic acid, among other interesting metabolites with antimicrobial activity. A cell-free supernatant (CFS) is a liquid containing the metabolites resulting from microbial growth and the residual nutrients of the medium used. CFS from LAB can have antimicrobial activity due to organic acids, fatty acids, and proteinaceous compounds, among other compounds. This review aims to summarize the information about CFS production, CFS composition, and the antimicrobial (antibacterial and antifungal) activity of CFS from LAB in vitro, on foods, and in active packaging. In addition, the mechanisms of action of CFS on cells, the stability of CFS during storage, CFS cytotoxicity, and the safety of CFS are reviewed. The main findings are that CFS's antibacterial and antifungal activity in vitro has been widely studied, particularly in members of the genus Lactobacillus. CFS has produced strong inhibition of bacteria and molds on foods when applied directly or in active packaging. In most studies, the compounds responsible for antimicrobial activity are identified. A few studies indicate that CFSs are stable for 1 to 5 months at temperatures ranging from 4 to 35°C. The cytotoxicity of CFS on human cells has not been well studied. However, the studies that have been performed reported no toxicity of CFS. Therefore, it is necessary to investigate novel growth mediums for CFS preparation that are compatible with food sensory properties. More studies into CFS stability and cytotoxic effects are also needed.

Background Lactic acid bacteria from fermented foods and fish can antagonistically inhibit the growth of foodborne pathogenic organism in fermented food and they stimulate the immune response to protect the fish from certain kinds of infections. The aim of this study was to evaluate the in vitro antagonistic activities of lactic acid bacteria isolated from fermented beverage (Borde) and finfish on foodborne pathogenic microorganisms. Methods Laboratory-based experimental study was conducted from May 1 to Sep 1, 2020. Total sample numbers were 60 samples of fermented beverage (Borde) and 20 of finfish which were collected from different households and Chamo Lake (Arba Minch, Ethiopia). Each sample was firstly homogenized and serial dilution was prepared and spread on MRS agar plates in order to isolate pure culture. Different biochemical tests were performed to identify isolated bacteria. Then, cell-free supernatant (CFS) was prepared from MRS culture and used in an antimicrobial assay that was performed by agar diffusion method. The effects of pH, temperature, and enzymes on antimicrobial activity were evaluated in the same test. Simultaneously, the effects of lactic acid bacteria on aflatoxin production and on the permeability of the membrane were also evaluated. Data were analyzed using one-way ANOVA and Tukey post hoc analysis was performed by SPSS 25 statistical software. Result A total of 40 lactic acid bacteria were isolated; among them, 4 lactic acid bacteria, belonging to the genera Enterococcus, Leuconostoc, and Weisellia from fermented beverage and Pediococcus from fish, were screened for antimicrobial activity. The cell-free supernatant of those four isolates exhibited a significant (p < 0.05) antibacterial effect against tested pathogens and foodborne pathogenic bacteria. In addition, CFS showed antifungal and antiaflatoxigenic activities. The antimicrobial compounds synthesized by these isolates were sensitive to some proteolytic enzymes, and they were proved to be stable at high temperatures. It maintained/retained antimicrobial activity in a wide range of pH 2.0–10. Enterococcal CFS exhibited antibacterial activity against S. aureus on membrane permeability, as confirmed by the increase in absorbance value between 0.075 and 0.24 at OD280-nm and between 0.68 and 1.2 at OD260-nm. Conclusion Cell-free supernatant produced by isolated lactic acid bacteria showed antimicrobial activity against a wide range of Gram-positive and Gram-negative foodborne bacteria, suggesting its potential application as a natural antimicrobial agent in tackling the rising drug resistance against foodborne pathogens.

Antifungal activity of lactobacilli and its relationship with 3-phenyllactic acid production

This study was performed to investigate the use of plant-based lactic acid bacteria (LAB) to reduce microbiological hazards in kimchi. Cell-free supernatants (CFS) from four LAB strains isolated from kimchi were tested for antimicrobial activity against five foodborne pathogens and two soft-rot pathogens. Each CFS showed antimicrobial activity against both foodborne and soft-rot pathogens. Washing salted kimchi cabbages inoculated with B. cereus with 5% CFS inhibited B. cereus to a greater extent than NaClO. The CFS from WiKim 83 and WiKim 87 exhibits inhibition rates of 25.09% and 24.21%, respectively, compared to the 19.19% rate of NaClO. Additionally, the CFS from WiKim 116 and WiKim 117 showed inhibition rates of 18.74% and 20.03%, respectively. Direct treatment of kimchi cabbage with soft-rot pathogens and CFS for five days inhibited the pathogens with similar efficacy to that of NaClO. To elucidate the antimicrobial activity mechanisms, pH neutralization, heat treatment, and organic acid analyses were performed. pH neutralization reduced the antimicrobial activity, whereas heat treatment did not, indicating that lactic, acetic, citric, and phenyllactic acids contribute to the thermal stability and antimicrobial properties of CFS. This study suggests that the four kimchi-derived LAB, which maintain a low pH through organic acid production, could be viable food preservatives capable of reducing biological hazards in kimchi.

Aim: To evaluate the antibacterial activity of lactic acid bacteria against selected food pathogens (Escherichia coli and Staphylococcus aureus). Method: A total of twenty (20) traditionally fermented food samples were purchased from a market in Owerri metropolis. Isolation and identification of lactic acid bacteria (LAB) were conducted using standard microbiological techniques. LAB was identified using standard morphological and biochemical tests. They were tested against food pathogens using the Agar well diffusion method. Results: The isolated lactic acid bacteria include Lactobacillus fermentum, Lactobacillus acidophilus, Lactobacillus casei and Lactobacillus plantarum and were label as SP1, SP2, SP3, and SP4 respectively. The isolated LAB species had a considerable inhibitory effect on food borne pathogens. Cell free supernatant of four species were tested for antagonistic activity at 24hrs and 48hrs incubation time. Cell free supernatant from 48hrs broth of SP1 showed the highest zone of inhibition on Escherichia coli (28mm) while the cell free supernatant from 24hrs broth of SP4 showed the lowest zone of inhibition on Staphylococcus aureus (13 mm). Conclusion: The antimicrobial activity increases with time. LAB demonstrated high antimicrobial properties against food borne pathogens. This potential can be employed as starters in food industry to inhibit food spoilage microbes and contaminants.

This paper aims at studying antimicrobial efficacy and in vitro cytoxic activity of epiphytic orchids namely Acampe praemorsa, Aeridis odorata distributed in Eastern Ghats of Visakhapatnam district. Plants were collected, identified following literature, shade dried and Methanol, ethyl acetate extracts were prepared for the systematic investigation of antimicrobial activity of plant extracts. Antibacterial activity against three gram positive bacteria Bacillus megaterium, Lactobacillus acidophillus and Enterococcus faecalis, three gram negative bacteria Proteus vulgaris, Klebsiella pneumoniae and Escherichia coli was done using Agar well diffusion method, antifungal activity was carried against Candida albicans, Aspergillus flavus by Cpzapak dox agar media, MIC by broth dilution method, zones of inhibition were recorded. Ethyl acetate extracts showed maximum antimicrobial activity against all bacteria and fungi, Aeridis odarata ethyl acetate extract showed highest zone of inhibition 17mm against Lactobacillus acidophilus in bacteria, Ethyl acetate extract of Acampe praemorsa showed highest zone of inhibition 17mm against Candida albicans in fungi, the leaf extracts were tested for its inhibitory effect on HeLa and MCF-7 cell lines were evaluated by the MTT assay and methanolic extract of Aeridis odarata has significant cytotoxicity effect on MCF-7 cell line in concentration range between 5 to 100µg/ml, with IC 50 (µg/ml) value is 26.2. These plants have good antimicrobial activity, further investigation on the phytochemistry of bioactive compounds of these plants would result in discovery of new drugs and further pharmacological investigation of anti-cancer activity of Aeridis odarata should be done.

Bacteriocins from lactic acid bacteria (LAB) are natural antimicrobial peptides or proteins with interesting potential applications in food preservation and health care. The present study was aimed to isolate bacteriocinogenic LAB from dairy products, fermented food and environmental waste samples. One thirty five colonies of LAB were isolated and screened for bacteriocin production by agar overlay method. Among them, Lactobacillus acidophilus NCIM5426 isolated from home made paneer showed maximum zone of inhibition i.e 22-24mm in diameter against food borne ( Listeria monocytogenes , Staphylococcus aureus ) and human pathogens ( Escherichia coli , Salmonella typhi ). The antibacterial compound from the culture supernatant was found to be proteinaceous in nature and therefore, identified as bacteriocin. The bacteriocin of L. acidophilus NCIM5426 was found to be heat-stable (121°C for 15 min) and active over a wide pH range of 4.0-10.0. It showed stability (60%) for 30 days at room temperature (30-32°C). Addition of surfactants (EDTA, SDS, Hexadecyl trimethylamonium bromide) up to 1% to crude bacteriocin showed increase in antibacterial activity where as metal ions (Calcium Chloride, Zinc Sulphate and Mercuric Chloride) in low concentration (0.5-1mgL -1 ) decreased the activity. The bacteriocin was purified to its homogeneity by ammonium sulfate precipitation followed by gel filtration chromatography and HPLC. Molecular weight of bacteriocin was found to be 5.6 and 5.8 KDa by SDS page and LC/MS respectively. Production and activity of bacteriocin was significant (50%) even at higher salt (NaCl) concentration i.e 3%. Our present study demonstrates the possibility of using L. acidophilus NCIM5426 or its bacteriocin as a biopreservative in dairy industry.

Green glutinous rice tape is a fermented food made from glutinous rice, katuk leaves (Sauropus androgynus), and yeast, originating from Tembilahan, Riau Province. This product can serve as a source of lactic acid bacteria (LAB) capable of producing antimicrobial compounds to inhibit pathogenic microorganisms, including Aspergillus flavus, a well-known spoilage fungus in food products. However, to date, no reports have explored the ability of LAB from green glutinous rice tape to inhibit the growth of Aspergillus flavus. This study aimed to isolate LAB from green glutinous rice tape, conduct macroscopic, microscopic, and biochemical characterizations, and evaluate the antifungal activity of the LAB isolates against Aspergillus flavus using the good diffusion method. The isolation process yielded four LAB isolates from Tembilahan green tape (TKHT-2, TKHT-3, TKHT-5, and TKHT-7), which were identified as members of the genus Lactobacillus sp., with antifungal activities of 25.50 ± 5.78 mm, 24.33 ± 0.62 mm, 22.16 ± 6.56 mm, and 18.66 ± 4.28 mm, respectively. The corresponding cell-free supernatants (CFS) from these isolates (TKHT-S2, TKHT-S3, TKHT-S5, and TKHT-S7) also demonstrated antifungal activity with inhibition zones of 19.83 ± 3.47 mm, 19.83 ± 4.24 mm, and 14.50 ± 3.26 mm, respectively. LAB cells and their cell-free supernatants partially inhibited Aspergillus flavus, indicating a fungistatic effect. These findings suggest the potential application of LAB from green glutinous rice tape as a natural preservative or antifungal agent in food products.

Antifungal activity determination for the peptides generated by Lactobacillus plantarum TE10 against Aspergillus flavus in maize seeds

Lactobacillus plantarum with broad antifungal activity: A promising approach to increase safety and shelf-life of cereal-based products

Biopreservation of tomatoes using fermented media by lactic acid bacteria

Background: There has been an increase in public health concern over post-harvest spoilage fungi in plantain. This study aimed to explore the role of Lactic Acid Bacteria (LAB) from fermented foods against spoilage fungi of plantain. Methods: Seventy-five LAB were isolated from agadagidi and ogi between February and April 2021. Cell-Free Supernatants (CFS) of the broth cultures were obtained by centrifugation. Spoilage fungi were obtained from plantain with visible mould growth. Initial screening of the LAB isolates for antifungal activities was carried out using the agar overlay method. The agar well diffusion method was used to assay the inhibitory spectrum of the CFS. Data obtained for the inhibition diameters were analysed using descriptive statistics (IBM SPSS 22). LAB isolates with the highest antifungal activity were assessed for their safety via the DNase, gelatinase, and haemolysis tests, and were identified by 16S rRNA sequencing. Results: Twenty-six LAB isolates exhibiting antifungal activity were obtained from the samples. The isolated spoilage fungi included Aspergillus flavus, Fusarium oxysporum, Fusarium verticilliodes, Penicillium sp, and Rhizopus sp. Nine of the 26 LAB isolates produced inhibition zones &gt;14 mm in diameter. The CFS of isolate 5AG8 had antifungal activity against the spores of A. flavus, F. oxysporum, and Penicillium sp. The CFS of isolate AG1 inhibited the mycelial growth of F. verticilliodes and Penicillium sp, while the CFS of isolate OP was active against the spores of A. flavus and Penicillium sp. None of the isolates tested positive in the safety assessment tests. The isolates were identified as Lactobacillus plantarum OP, L. plantarum AG1, and Lactobacillus fermentum 5AG8. Conclusion: This study revealed that LAB strains from agadagidi and ogi are safe for use in food matrices and their metabolites can be used in the control of spoilage fungi in plantain.

Contamination of Aspergillus flavus can attacks food and feed ingredients, especially seeds during the storage. The using of biological agents, like microbes that have antifungal activity becomes a promising and important solution to be studied. This research aims to find out the antifungal activity of lactic acid bacteria (LAB) from digestive tract of “Kampung” chickens against the growing of A. flavus. Source of the isolates are from colon, ventriculus, and crop. The inoculums of LAB which using were suspension of cell and cell free supernatant (CFS). There were 6 isolates of LAB (Bub1, Bub3, Bub4, V52, C51, and NNB) tested to obtain the potential of antifungal activity, by with well diffusion and and submerged culture method. The results showed that the 5 isolates suspension cell of LAB showed inhibitory zones, except Bub1, whereas all CFS LAB showed the inhibitory zones against the growth of A. flavus in MRSA medium. Furthermore, antifungal activity of LAB against A. flavus to be observed by measuring the dry weight of the mycelium production, as well as the percentage of inhibition during the incubation period. All isolates of LAB, from suspension cell and CFS showing antifungal activity against growth of A. flavus. The Bub3 and NNB isolates, from suspension cell and CFS showed that the best antifungal activity compared to the others.

Black cherry fruit as a source of probiotic candidates with antimicrobial and antibiofilm activities against Salmonella

This study was carried out to investigate the effect of LAB (Lactic acid bacteria: Lactobacillus acidophilus, Bifidobacterium bifidum and Streptococcus thermophilus) on detoxication of damaged liver in carbon tetrachloride (<TEX>$CCl_4$</TEX>) and ethanol (25%)-treated rats. Rats had been daily (twice a day) pre-treated with saline (0.5 ml/kg: untreated group), <TEX>$CCl_4$</TEX> (0.5 ml/kg: other groups) for 6 days. At seventh day, after treating rat with <TEX>$CCl_4$</TEX> and then, mixture of LAB (<TEX>$10^{11}$</TEX>/0.5 ml: LAB group), saline (0.5 ml/kg: untreated group, <TEX>$CCl_4$</TEX> group), and biphenyl dimethyl dicarboxylate (DDB) (50 mg/kg: DDB group) were treated orally with <TEX>$CCl_4$</TEX> for 8 days. Ethanol is treated as the same manner instead of <TEX>$CCl_4$</TEX>. To investigate the hepatoprotective effect, rats treated with <TEX>$CCl_4$</TEX> and ethanol were analyzed with serum GOT and GPT level. The GOT and GPT levels of LAB group was lower than the level of <TEX>$CCl_4$</TEX> and DDB group. Especially, compared with data of <TEX>$CCl_4$</TEX> group, GPT activity showed statistically significant result in the significance level of p < 0.05. The LAB group treated with ethanol also showed lower level of GOT and GPT than the other control groups treated with ethanol. The triglyceride level of serum decreased more in a group treated special materials (DDB and LAB group) than ethanol group. As well, the effect of LAB on the antifatigue has been investigated. The animals (10/group) were divided into 4 groups (untreated group, Carrier group, Red-ginseng group, LAB group). Each group was given carrier (0.9 mg/0.2 ml), red ginseng extract (200 mg/kg), and mixture of LAB (<TEX>$10^{11}$</TEX>/0.2 ml). Special materials were given for three weeks. After finishing treating through oral, horizontal wire test, rotarod test, and forced swimming test were performed. The time of resistance to fatigue of the group, fed with mixture of LAB, was longer than the time when mice treated with red-ginseng that the effect was already revealed. The result of this study revealed that LAB could decrease hepatocelluar injury compared with rats treated orally with <TEX>$CCl_4$</TEX> and ethanol, and could also decrease fatigue.