*Corresponding Author: Dr.R Mahenthiran, Assistant Professor, PG and Research, Department of Microbiology,
Dr.N.G.P. Arts and Science College, Coimbatore- 641048. Email: [email protected]. 83
International Journal of Zoology and Applied Biosciences ISSN: 2455-9571
Volume 10, Issue 5, pp: 83-88, 2025 http://www.ijzab.com
https://doi.org/10.55126/ijzab.2025.v10.i05.011
Research Article
EXPLORING THE ANTIMICROBIAL ATTRIBUTE: CHARACTERIZATION
OF LACTOBACILLUS ISOLATE AND IN VITRO ASSESSMENT OF
ANTIMICROBIAL ACTIVITY OF POSTBIOTIC CELL-FREE
SUPERNATANTS AGAINST PATHOGENIC MICROORGANISMS
Arunavarsini Kumarasamy and * R Mahenthiran
PG and Research, Department of Microbiology, Dr.N.G.P. Arts and Science College, Coimbatore- 641048.
Article History: Received 31st July 2025; Accepted 13th September 2025; Published 30th September 2025
ABSTRACT
This study examines the antimicrobial potential of the cell-free supernatant of a Lactobacillus isolate. The isolate
was identified accurately by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-
TOF MS). Antimicrobial potential against four common pathogenic bacteria, namely Escherichia coli,
Enterococcus faecalis, Salmonella enterica, and Streptococcus bovis, was determined by agar well diffusion assay.
The results demonstrated concentration-dependent increases in inhibition zones for all tested pathogens; the
postbiotic showed significant antimicrobial potential similar to reference antibiotics. This study demonstrates the
potential of probiotic cell-free supernatant as a bioactive postbiotic agent that can inhibit pathogenic bacteria, thus
providing alternative infection control. The results also suggest the potential of the postbiotic in being developed as
a bioactive antimicrobial agent for infection management.
Keywords: Yogurt, Postbiotic, Cell free supernatant, Pathogenic bacteria and Antimicrobial activity.
INTRODUCTION
Fermented products like yogurt have gained widespread
acclaim for their probiotic effects, a considerable amount of
which has been attributed to the live and active cultures of
helpful bacteria like Lactobacillus and Bifidobacterium
with which yogurt is prepared. The probiotics ensure the
establishment of a healthy gut microbiota that is vital for
maintaining digestive health, enhancing nutrient
assimilation, and preventing gastrointestinal upsets
(Hadjimbei et al., 2022). Daily intake of probiotic yogurt
has been associated with improved immune function, less
inflammation, and possibly a reduced risk of infections in
the gastrointestinal and respiratory tracts. Yogurt also
supplies vital nutrients, such as calcium, vitamin D, and
protein, which help build bones and provide general
nutrition (Yadav et al., 2015). There is also evidence that
probiotic yogurt can help control symptoms of lactose
intolerance, decrease the duration of infectious diarrhea,
and be involved in preventing chronic conditions like
osteoporosis, diabetes, and cardiovascular diseases. The
exclusive blend of live probiotic cultures and nutrient-
dense matrix of yogurt makes it an ideal vehicle for
transferring beneficial bacteria to the human gut (Meybodi
et al., 2020).
Probiotics isolated from yogurt consist predominantly of
strains such as Lactobacillus delbrueckii subsp. bulgaricus,
Lactiplantibacillus plantarum, Lactobacillus acidophilus,
Bifidobacterium bifidum, and Lactobacillus casei.
Probiotics not only enrich the nutritional content of yogurt
but also contribute towards health advantages such as the
inhibition of pathogens and improved gut health. Literature
shows that use of specific Lactobacillus and
Bifidobacterium strains in yogurt results in products with
probiotic viability at storage temperatures and reduces
desired physicochemical and sensory characteristics.
Particularly, yogurts containing Lactobacillus plantarum or
Lactobacillus casei have improved texture and organoleptic
attributes, while multi-strain mixtures can also increase
Arunavarsini Kumarasamy and R Mahenthiran Int. J. Zool. Appl. Biosci., 10(5), 83-88, 2025
www.ijzab.com
probiotic functionality and quality of the product. The
stability and effectiveness of these probiotic
microorganisms make yogurt an excellent delivery vehicle
for beneficial microbes to humans (Hoxha et al., 2023).
Postbiotics are preparations from inanimate (non-viable)
microorganisms and their fractions that confer a health
benefit to the host. Differing from probiotics with the need
for live microorganisms, postbiotics are made from
inactivated microbial cells, cell fractions, or both—
occasionally with their metabolic end products. This novel
idea was developed in response to worries about the safety
and viability of probiotics and hence interest in applying
microbial cell components and metabolites that offer a
beneficial effect without any living organisms. Postbiotics
can improve health by modulating the immune response,
improving epithelial barrier function, and influencing other
physiological activities (Ma et al., 2023).
Bioactive postbiotic metabolites have a diverse collection
of molecules produced by probiotic bacteria during
fermentation and include short-chain fatty acids (SCFAs),
exopolysaccharides, bacteriocins, antioxidant enzymes, cell
wall fragments, and other metabolic byproducts.
Metabolites have many health-influential activities, such as
antimicrobial, antioxidant, anticancer, anti-inflammatory,
and immunomodulatory activities (Hijová E. 2024). Short-
chain fatty acids such as butyrate, acetate and propionate
Support intestinal health by reducing intestinal pH,
regulating the immune response, and improving nutrient
uptake (Asefa et al., 2025). Exopolysaccharides that
promote the growth of the beneficial gut bacteria and aid
module immune function. Bacteriocins and cell-free
supernatants show effective antimicrobial activity against
numerous pathogens. Enzymes and peptides add
antioxidant activity and can decrease inflammation. These
bioactice molecules may be safely delivered as postbiotics
without the potential negative consequences of live
probiotic intake, providing a stable predictable method for
enhancing health outcome (Pattapulavar et al.,2025) The
purpose of this research is to isolate and characterize
Lactiplanti bacillus plantarum from homemade yogurt,
screen its probiotic attributes, and assess the antimicrobial
efficacy of its cell-free supernatant (also known as
postbiotic) against typical pathogens. The results join the
increasing body of evidence that validates the use of
postbiotics obtained from probiotics in health promotion,
thereby opening the door to their safe use in therapeutic
regimens.
MATERIALS AND METHODS
Sample preparation and isolation
Overnight fermented homemade yogurt was collected. 10
ml of sample isolated in 100 ml of de Man, Rogosa, and
Sharpe (MRS) Broth at 37 °C for 24–48 hours. Layter, it
was streaked in de Man, Rogosa, and Sharpe (MRS) agar
for 24 hours at 37℃. After subsequent culturing pure
culture is obtained (Abdel et al., 20).
Morphological and Biochemical characterization
The identification and further morphological
characterization of LAB was identified using microscopic
observation that is by gram staining. For biochemical
characterization IMVic, catalase and oxidase was
performed.
MALDI-TOF
Followed by Biochemical characterization, MALDI-TOF
MS (matrix-assisted laser desorption ionization time of
flight mass spectrometry)-based VITEK MS PRIME for
molecular identification of the isolated lactobacillus strain.
Cell free supernatant- postbiotic
Overnight fresh culture of isolated lactobacillus strain was
centrifuged at 6000 rpm for 10 minutes. The cells was
removed by 22μm membrane filter to obtain postbiotic cell
free supernatant.
Antimicrobial activity
The antibacterial activity was done by agar well diffusion
method. Escherichia coli, Streptococcus bovis,
Enterococcus faecalis and Salmonella enterica was used
for the antibacterial activity. These four strains were
inoculated overnight in LB broth. Muller Hinton Agar was
prepared and poured into sterile petri plates. Overnight
incubated strains were swabbed in the freshely poured
MHA agar plated. And well was cut for 4 different
concentrations like 25, 50, 75 and 100 to load the postbiotic
cell free supernatant along with the standard antibiotic disc.
The zone of inhibition was measured in mm.
RESULTS AND DISCUSSION
The isolated probiotic strain possessed standard
morphological and microscopic features of lactic acid
bacteria. Morphologically, the colonies were small,
circular, and off-white in color. Microscopically, Gram
staining revealed that the bacteria had a Gram-positive rod-
shaped (bacilli) morphology. These results establish the
identity of the isolate as a Lactobacillus species.
Biochemical analysis of the Lactobacillus strain
confirmed a number of significant characteristics similar to
those of probiotic lactobacilli. The test result for the methyl
red was positive, showing that the bacteria were actively
producing acid during fermentation. On the other hand, the
test results for indole production, Voges-Proskauer
reaction, citrate utilization, catalase, and oxidase activity
were negative, indicating that the bacteria are incapable of
producing indole, not fermenting citrate, and not producing
catalase or oxidase enzymes. These biochemical properties
are characteristic of Lactobacillus species, affirming their
function as producers of lactic acid and substantiating their
potential probiotic features (Table 1).
www.ijzab.com
probiotic functionality and quality of the product. The
stability and effectiveness of these probiotic
microorganisms make yogurt an excellent delivery vehicle
for beneficial microbes to humans (Hoxha et al., 2023).
Postbiotics are preparations from inanimate (non-viable)
microorganisms and their fractions that confer a health
benefit to the host. Differing from probiotics with the need
for live microorganisms, postbiotics are made from
inactivated microbial cells, cell fractions, or both—
occasionally with their metabolic end products. This novel
idea was developed in response to worries about the safety
and viability of probiotics and hence interest in applying
microbial cell components and metabolites that offer a
beneficial effect without any living organisms. Postbiotics
can improve health by modulating the immune response,
improving epithelial barrier function, and influencing other
physiological activities (Ma et al., 2023).
Bioactive postbiotic metabolites have a diverse collection
of molecules produced by probiotic bacteria during
fermentation and include short-chain fatty acids (SCFAs),
exopolysaccharides, bacteriocins, antioxidant enzymes, cell
wall fragments, and other metabolic byproducts.
Metabolites have many health-influential activities, such as
antimicrobial, antioxidant, anticancer, anti-inflammatory,
and immunomodulatory activities (Hijová E. 2024). Short-
chain fatty acids such as butyrate, acetate and propionate
Support intestinal health by reducing intestinal pH,
regulating the immune response, and improving nutrient
uptake (Asefa et al., 2025). Exopolysaccharides that
promote the growth of the beneficial gut bacteria and aid
module immune function. Bacteriocins and cell-free
supernatants show effective antimicrobial activity against
numerous pathogens. Enzymes and peptides add
antioxidant activity and can decrease inflammation. These
bioactice molecules may be safely delivered as postbiotics
without the potential negative consequences of live
probiotic intake, providing a stable predictable method for
enhancing health outcome (Pattapulavar et al.,2025) The
purpose of this research is to isolate and characterize
Lactiplanti bacillus plantarum from homemade yogurt,
screen its probiotic attributes, and assess the antimicrobial
efficacy of its cell-free supernatant (also known as
postbiotic) against typical pathogens. The results join the
increasing body of evidence that validates the use of
postbiotics obtained from probiotics in health promotion,
thereby opening the door to their safe use in therapeutic
regimens.
MATERIALS AND METHODS
Sample preparation and isolation
Overnight fermented homemade yogurt was collected. 10
ml of sample isolated in 100 ml of de Man, Rogosa, and
Sharpe (MRS) Broth at 37 °C for 24–48 hours. Layter, it
was streaked in de Man, Rogosa, and Sharpe (MRS) agar
for 24 hours at 37℃. After subsequent culturing pure
culture is obtained (Abdel et al., 20).
Morphological and Biochemical characterization
The identification and further morphological
characterization of LAB was identified using microscopic
observation that is by gram staining. For biochemical
characterization IMVic, catalase and oxidase was
performed.
MALDI-TOF
Followed by Biochemical characterization, MALDI-TOF
MS (matrix-assisted laser desorption ionization time of
flight mass spectrometry)-based VITEK MS PRIME for
molecular identification of the isolated lactobacillus strain.
Cell free supernatant- postbiotic
Overnight fresh culture of isolated lactobacillus strain was
centrifuged at 6000 rpm for 10 minutes. The cells was
removed by 22μm membrane filter to obtain postbiotic cell
free supernatant.
Antimicrobial activity
The antibacterial activity was done by agar well diffusion
method. Escherichia coli, Streptococcus bovis,
Enterococcus faecalis and Salmonella enterica was used
for the antibacterial activity. These four strains were
inoculated overnight in LB broth. Muller Hinton Agar was
prepared and poured into sterile petri plates. Overnight
incubated strains were swabbed in the freshely poured
MHA agar plated. And well was cut for 4 different
concentrations like 25, 50, 75 and 100 to load the postbiotic
cell free supernatant along with the standard antibiotic disc.
The zone of inhibition was measured in mm.
RESULTS AND DISCUSSION
The isolated probiotic strain possessed standard
morphological and microscopic features of lactic acid
bacteria. Morphologically, the colonies were small,
circular, and off-white in color. Microscopically, Gram
staining revealed that the bacteria had a Gram-positive rod-
shaped (bacilli) morphology. These results establish the
identity of the isolate as a Lactobacillus species.
Biochemical analysis of the Lactobacillus strain
confirmed a number of significant characteristics similar to
those of probiotic lactobacilli. The test result for the methyl
red was positive, showing that the bacteria were actively
producing acid during fermentation. On the other hand, the
test results for indole production, Voges-Proskauer
reaction, citrate utilization, catalase, and oxidase activity
were negative, indicating that the bacteria are incapable of
producing indole, not fermenting citrate, and not producing
catalase or oxidase enzymes. These biochemical properties
are characteristic of Lactobacillus species, affirming their
function as producers of lactic acid and substantiating their
potential probiotic features (Table 1).
Arunavarsini Kumarasamy and R Mahenthiran Int. J. Zool. Appl. Biosci., 10(5), 83-88, 2025
www.ijzab.com
Table 1. Morphology, Microscopic and Biochemical characterization.
S.No Characterization Test Observation
1. Morphology Colony morphology Small round colonies
Appearance Off- white
2. Microscopic Gram staining Gram positive
Structure Rod shaped bacilli
3. Biochemical Indole -ve
Methyl red +ve
Voges proskauer -ve
Citrate utilization -ve
Catalase -ve
Oxidase -ve
The bacterial isolate was identified by molecular
identification with matrix-assisted laser desorption
ionization time-of-flight mass spectrometry (MALDI-TOF
MS) facilitated by the VITEK MS PRIME system. The
MALDI-TOF MS identification resulted in a distinct
protein spectral pattern that corresponded with a large
database of previously entered bacterial strains. The
identification resulted in a confidence level of over 99.9%,
thereby confirming the strain to be Lactiplantibacillus
plantarum. The identification was validated by technical
replicate tests, which affirm the reproducibility and
reliability of the technique. The antimicrobial activity of the
probiotic cell-free supernatant against selected pathogenic
bacteria was evaluated using the agar well diffusion assay.
The zones of inhibition were measured in mm for each
pathogen at different concentrations of the supernatant of
25 μl, 50 μl, 75 μl, and 100 μl (Table 2).
Table 2. Zone of inhibition (mm) of postbiotics cell free supernatant.
S. No Microorganisms Zone of inhibition of postbiotic along with standard antibiotics
25μl 50 μl 75 μl 100 μl Standard antibiotics
1. Enterococcus faecalis - 10mm 11mm 14mm Amplicillin 14.5mm
2. Escherichia coli 8mm 11mm 13mm 15mm Penicillin 17mm
3. Streptococcus bovis - 9mm 10mm 13mm Vancomycin 15mm
4. Salmonella enterica - 8mm 12mm 16mm Azithromycin 18mm
Among the pathogens, Salmonella enterica was the most
sensitive to the postbiotic, with a maximum inhibition of 16
mm at 100 μL, almost reaching the zone of inhibition seen
with azithromycin (18 mm). Escherichia coli was also the
most sensitive, with a 15 mm zone at the highest
concentration. No inhibition was detected at 25 μL for
Enterococcus faecalis, Streptococcus bovis, and Salmonella
enterica, indicating that a minimum effective concentration
is necessary for antimicrobial activity. Enterococcus
faecalis and Streptococcus bovis had moderate inhibition of
14 mm and 13 mm, respectively, at 100 μL against
comparative antibiotic controls. The antimicrobial activity
of the postbiotic supernatant increased progressively with
volume, with a clear dose-response profile for all of the
bacteria tested.
In the present study, Lactobacillus strain was isolated from
homemade yogurt and confirmed through a combined
approach of morphological, biochemical, and MALDI-TOF
MS identification. The subsequent preparation of the cell-
free supernatant (postbiotic) from this probiotic isolate
demonstrated marked in vitro antimicrobial activity against
major clinical pathogens, namely Escherichia coli,
Enterococcus faecalis, Salmonella enterica, and
Streptococcus bovis. The activity observed was both
concentration-dependent and substantial, approaching that
of standard antibiotics in certain cases. The results of the
present study complement and supplement previous work
that identifies yogurt as a major source of probiotic strains,
particularly of the Lactobacillus and Lactiplantibacillus
genera. Subsequent publications (Harat et al., 2025; Liang
et al., 2023) have described the importance of strain
identification and the potential functional properties
displayed by some yogurt-based isolates. Our work also
complements the finding that traditional fermented foods
remain a valuable reservoir for candidate probiotic
screening, as documented in other global research (Goa et
al., 2022).
The isolated postbiotic of L. plantarum was reported to
possess strong antimicrobial activity. The finding supports
the novel hypothesis among researchers that cell-free
probiotic preparations of organic acids, bacteriocins,
peptides, exopolysaccharides, and other metabolites can
have strong inhibitory activity on a variety of pathogens
(Aguilar-Toalá et al., 2018; Moradi et al., 2020). This study
by (Gurunathan et al., 2023) points out postbiotics as a
viable and safer alternative to conventional probiotics since
www.ijzab.com
Table 1. Morphology, Microscopic and Biochemical characterization.
S.No Characterization Test Observation
1. Morphology Colony morphology Small round colonies
Appearance Off- white
2. Microscopic Gram staining Gram positive
Structure Rod shaped bacilli
3. Biochemical Indole -ve
Methyl red +ve
Voges proskauer -ve
Citrate utilization -ve
Catalase -ve
Oxidase -ve
The bacterial isolate was identified by molecular
identification with matrix-assisted laser desorption
ionization time-of-flight mass spectrometry (MALDI-TOF
MS) facilitated by the VITEK MS PRIME system. The
MALDI-TOF MS identification resulted in a distinct
protein spectral pattern that corresponded with a large
database of previously entered bacterial strains. The
identification resulted in a confidence level of over 99.9%,
thereby confirming the strain to be Lactiplantibacillus
plantarum. The identification was validated by technical
replicate tests, which affirm the reproducibility and
reliability of the technique. The antimicrobial activity of the
probiotic cell-free supernatant against selected pathogenic
bacteria was evaluated using the agar well diffusion assay.
The zones of inhibition were measured in mm for each
pathogen at different concentrations of the supernatant of
25 μl, 50 μl, 75 μl, and 100 μl (Table 2).
Table 2. Zone of inhibition (mm) of postbiotics cell free supernatant.
S. No Microorganisms Zone of inhibition of postbiotic along with standard antibiotics
25μl 50 μl 75 μl 100 μl Standard antibiotics
1. Enterococcus faecalis - 10mm 11mm 14mm Amplicillin 14.5mm
2. Escherichia coli 8mm 11mm 13mm 15mm Penicillin 17mm
3. Streptococcus bovis - 9mm 10mm 13mm Vancomycin 15mm
4. Salmonella enterica - 8mm 12mm 16mm Azithromycin 18mm
Among the pathogens, Salmonella enterica was the most
sensitive to the postbiotic, with a maximum inhibition of 16
mm at 100 μL, almost reaching the zone of inhibition seen
with azithromycin (18 mm). Escherichia coli was also the
most sensitive, with a 15 mm zone at the highest
concentration. No inhibition was detected at 25 μL for
Enterococcus faecalis, Streptococcus bovis, and Salmonella
enterica, indicating that a minimum effective concentration
is necessary for antimicrobial activity. Enterococcus
faecalis and Streptococcus bovis had moderate inhibition of
14 mm and 13 mm, respectively, at 100 μL against
comparative antibiotic controls. The antimicrobial activity
of the postbiotic supernatant increased progressively with
volume, with a clear dose-response profile for all of the
bacteria tested.
In the present study, Lactobacillus strain was isolated from
homemade yogurt and confirmed through a combined
approach of morphological, biochemical, and MALDI-TOF
MS identification. The subsequent preparation of the cell-
free supernatant (postbiotic) from this probiotic isolate
demonstrated marked in vitro antimicrobial activity against
major clinical pathogens, namely Escherichia coli,
Enterococcus faecalis, Salmonella enterica, and
Streptococcus bovis. The activity observed was both
concentration-dependent and substantial, approaching that
of standard antibiotics in certain cases. The results of the
present study complement and supplement previous work
that identifies yogurt as a major source of probiotic strains,
particularly of the Lactobacillus and Lactiplantibacillus
genera. Subsequent publications (Harat et al., 2025; Liang
et al., 2023) have described the importance of strain
identification and the potential functional properties
displayed by some yogurt-based isolates. Our work also
complements the finding that traditional fermented foods
remain a valuable reservoir for candidate probiotic
screening, as documented in other global research (Goa et
al., 2022).
The isolated postbiotic of L. plantarum was reported to
possess strong antimicrobial activity. The finding supports
the novel hypothesis among researchers that cell-free
probiotic preparations of organic acids, bacteriocins,
peptides, exopolysaccharides, and other metabolites can
have strong inhibitory activity on a variety of pathogens
(Aguilar-Toalá et al., 2018; Moradi et al., 2020). This study
by (Gurunathan et al., 2023) points out postbiotics as a
viable and safer alternative to conventional probiotics since
Arunavarsini Kumarasamy and R Mahenthiran Int. J. Zool. Appl. Biosci., 10(5), 83-88, 2025
www.ijzab.com
their efficacy is sustained even in the absence of live
microorganisms and with additional stability and
predictability. Mechanistically, our findings echo those of
(Ibrahim et al., 2021), who demonstrated that postbiotics
not only lower environmental pH through organic acid
release but may also disrupt pathogen cell membranes,
impair quorum sensing, or even induce DNA damage,
collectively contributing to bacterial cell death. Notably,
the robust inhibition of Salmonella enterica and
Escherichia coli by the postbiotic in this research supports
its potential utility as promising results reported for L.
plantarum-derived postbiotics in similar model systems
(Tong et al., 2025).
However, there are some limitations to be noted. The
method utilized, agar well diffusion, is standard for initial
assessments but doesn't replicate the conditions found in
complex food matrices or in the human gastrointestinal
tract. Moreover, the specific range and molecular topology
of the antimicrobial molecules present in our postbiotic
extract have not been found. Future research involving in
vivo efficacy trials, other pathogen assessments, and
metabolomic profiling may shed light on these aspects and
enable the identification of beneficial applications (Ji et al.,
2023; Homayouni et al., 2020). The synergy of these
antimicrobial and health-enhancing attributes highlights the
potential value of postbiotic strategies to human health.
However, with the optimistic nature of in vitro findings, are
warranted to finally determine the safety, effectiveness, and
functional advantages of postbiotics prior to their regular
use in a clinical environment.
CONCLUSION
This research study provides comprehensive information on
the isolation, characterization, and evaluation of the
probiotic ability of Lactiplanti bacillus plantarum from
homemade yogurt. Based on morphological, biochemical,
and molecular identification methods, the strain was
determined to possess characteristics of typical probiotic
lactobacilli, such as a Gram-positive rod shape, ability to
produce acid, and specific enzymatic activities. Cell-free
supernatant (postbiotic) preparation expressed high
antimicrobial activity against major foodborne pathogens
such as Escherichia coli, Enterococcus faecalis, Salmonella
enterica, and Streptococcus bovis, with the zones of
inhibition being concentration-dependent, up to the level of
effectiveness of standard antibiotics. The finding indicates
the strong antimicrobial activity of probiotic postbiotics,
which act by several modes, including cell membrane
disruption of bacteria and induction of DNA damage to
genomic DNA, leading to cell death of bacteria. The
bioactive molecules, which are mainly organic acids and
bacteriocins, are of high potential as replacements for
synthetic preservatives and antibiotics at a time of growing
concerns regarding antimicrobial resistance. Additionally,
the study brings into focus fermented food, with yogurt
being a prominent one, as a natural source of healthy
microbes that possess high probiotic and antimicrobial
activities. The efficiency and efficacy of probiotic cultures
such as Lactiplanti bacillus plantarum in yogurt foods are
of immense potential as effective modes for the delivery of
health-improving microbes to consumers, thus providing
benefits such as improved gastrointestinal health, immune
system balance, and resistance to disease. The complete
characterization and proof of antimicrobial activity
constitute the solid foundation for the prospective
utilization of postbiotics in therapeutic applications.
Additional in vivo studies are required to authenticate the
safety, bioavailability, and health-enhancing activity of
these probiotic strains and their metabolites. In conclusion,
this study highlights the potential in using natural probiotic
materials and their bioactive molecules towards the
improvement of food security, human health enhancement,
and the resolution of antimicrobial resistance issues,
thereby allowing the promotion of food functional
technology and microbiological safety regulations.
ACKNOWLEDGMENT
The authors express their sincere thanks to PG and
Research, Department of Microbiology, Dr.N.G.P. Arts and
Science College, Coimbatore for supporting the research
work.
CONFLICT OF INTERESTS
The authors declare no conflict of interest
ETHICS APPROVAL
Not applicable
FUNDING
This study received no specific funding from public,
commercial, or not-for-profit funding agencies.
AI TOOL DECLARATION
The authors declares that no AI and related tools are used to
write the scientific content of this manuscript.
DATA AVAILABILITY
Data will be available on request
REFERENCES
Abdel Tawab, F. I., Abd Elkadr, M. H., Sultan, A. M.,
Hamed, E. O., El-Zayat, A. S., & Ahmed, M. N. (2023).
Probiotic potentials of lactic acid bacteria isolated from
Egyptian fermented food. Scientific Reports, 13(1),
16601. https://doi.org/10.1038/s41598-023-16601
Aguilar-Toalá, J. E., Garcia-Varela, R., Garcia, H. S.,
Mata-Haro, V., González-Córdova, A. F., Vallejo-
Cordoba, B., & Hernández-Mendoza, A. (2018).
Postbiotics: An evolving term within the functional foods
field. Trends in Food Science & Technology, 75, 105–
114. https://doi.org/10.1016/j.tifs.2018.03.009
www.ijzab.com
their efficacy is sustained even in the absence of live
microorganisms and with additional stability and
predictability. Mechanistically, our findings echo those of
(Ibrahim et al., 2021), who demonstrated that postbiotics
not only lower environmental pH through organic acid
release but may also disrupt pathogen cell membranes,
impair quorum sensing, or even induce DNA damage,
collectively contributing to bacterial cell death. Notably,
the robust inhibition of Salmonella enterica and
Escherichia coli by the postbiotic in this research supports
its potential utility as promising results reported for L.
plantarum-derived postbiotics in similar model systems
(Tong et al., 2025).
However, there are some limitations to be noted. The
method utilized, agar well diffusion, is standard for initial
assessments but doesn't replicate the conditions found in
complex food matrices or in the human gastrointestinal
tract. Moreover, the specific range and molecular topology
of the antimicrobial molecules present in our postbiotic
extract have not been found. Future research involving in
vivo efficacy trials, other pathogen assessments, and
metabolomic profiling may shed light on these aspects and
enable the identification of beneficial applications (Ji et al.,
2023; Homayouni et al., 2020). The synergy of these
antimicrobial and health-enhancing attributes highlights the
potential value of postbiotic strategies to human health.
However, with the optimistic nature of in vitro findings, are
warranted to finally determine the safety, effectiveness, and
functional advantages of postbiotics prior to their regular
use in a clinical environment.
CONCLUSION
This research study provides comprehensive information on
the isolation, characterization, and evaluation of the
probiotic ability of Lactiplanti bacillus plantarum from
homemade yogurt. Based on morphological, biochemical,
and molecular identification methods, the strain was
determined to possess characteristics of typical probiotic
lactobacilli, such as a Gram-positive rod shape, ability to
produce acid, and specific enzymatic activities. Cell-free
supernatant (postbiotic) preparation expressed high
antimicrobial activity against major foodborne pathogens
such as Escherichia coli, Enterococcus faecalis, Salmonella
enterica, and Streptococcus bovis, with the zones of
inhibition being concentration-dependent, up to the level of
effectiveness of standard antibiotics. The finding indicates
the strong antimicrobial activity of probiotic postbiotics,
which act by several modes, including cell membrane
disruption of bacteria and induction of DNA damage to
genomic DNA, leading to cell death of bacteria. The
bioactive molecules, which are mainly organic acids and
bacteriocins, are of high potential as replacements for
synthetic preservatives and antibiotics at a time of growing
concerns regarding antimicrobial resistance. Additionally,
the study brings into focus fermented food, with yogurt
being a prominent one, as a natural source of healthy
microbes that possess high probiotic and antimicrobial
activities. The efficiency and efficacy of probiotic cultures
such as Lactiplanti bacillus plantarum in yogurt foods are
of immense potential as effective modes for the delivery of
health-improving microbes to consumers, thus providing
benefits such as improved gastrointestinal health, immune
system balance, and resistance to disease. The complete
characterization and proof of antimicrobial activity
constitute the solid foundation for the prospective
utilization of postbiotics in therapeutic applications.
Additional in vivo studies are required to authenticate the
safety, bioavailability, and health-enhancing activity of
these probiotic strains and their metabolites. In conclusion,
this study highlights the potential in using natural probiotic
materials and their bioactive molecules towards the
improvement of food security, human health enhancement,
and the resolution of antimicrobial resistance issues,
thereby allowing the promotion of food functional
technology and microbiological safety regulations.
ACKNOWLEDGMENT
The authors express their sincere thanks to PG and
Research, Department of Microbiology, Dr.N.G.P. Arts and
Science College, Coimbatore for supporting the research
work.
CONFLICT OF INTERESTS
The authors declare no conflict of interest
ETHICS APPROVAL
Not applicable
FUNDING
This study received no specific funding from public,
commercial, or not-for-profit funding agencies.
AI TOOL DECLARATION
The authors declares that no AI and related tools are used to
write the scientific content of this manuscript.
DATA AVAILABILITY
Data will be available on request
REFERENCES
Abdel Tawab, F. I., Abd Elkadr, M. H., Sultan, A. M.,
Hamed, E. O., El-Zayat, A. S., & Ahmed, M. N. (2023).
Probiotic potentials of lactic acid bacteria isolated from
Egyptian fermented food. Scientific Reports, 13(1),
16601. https://doi.org/10.1038/s41598-023-16601
Aguilar-Toalá, J. E., Garcia-Varela, R., Garcia, H. S.,
Mata-Haro, V., González-Córdova, A. F., Vallejo-
Cordoba, B., & Hernández-Mendoza, A. (2018).
Postbiotics: An evolving term within the functional foods
field. Trends in Food Science & Technology, 75, 105–
114. https://doi.org/10.1016/j.tifs.2018.03.009
Arunavarsini Kumarasamy and R Mahenthiran Int. J. Zool. Appl. Biosci., 10(5), 83-88, 2025
www.ijzab.com
Asefa, Z., Belay, A., Welelaw, E., & Haile, M. (2025).
Postbiotics and their biotherapeutic potential for chronic
disease and their feature perspective: A review. Frontiers
in Microbiomes, 4, 1489339.
https://doi.org/10.3389/frmbi.2025.1489339
Bhardwaj, A., Puniya, M., Sangu, K. P. S., Kumar, S., &
Dhewa, T. (2012). Isolation and biochemical
characterization of Lactobacillus species isolated from
Dahi. Research & Reviews: A Journal of Dairy Science
and Technology, 1(2), 1–14.
Drumond, M. M., Tapia-Costa, A. P., Neumann, E., Nunes,
Á. C., Barbosa, J. W., Kassuha, D. E., & Mancha-Agresti,
P. (2023). Cell-free supernatant of probiotic bacteria
exerted antibiofilm and antibacterial activities against
Pseudomonas aeruginosa: A novel biotic therapy.
Frontiers in Pharmacology, 14, 1152588.
https://doi.org/10.3389/fphar.2023.1152588
Goa, T., Beyene, G., Mekonnen, M., & Gorems, K. (2022).
Isolation and characterization of lactic acid bacteria from
fermented milk produced in Jimma Town, Southwest
Ethiopia, and evaluation of their antimicrobial activity
against selected pathogenic bacteria. International
Journal of Food Science, 2022, 2076021.
https://doi.org/10.1155/2022/2076021
Gurunathan, S., Thangaraj, P., & Kim, J. H. (2023).
Postbiotics: Functional food materials and therapeutic
agents for cancer, diabetes, and inflammatory diseases.
Foods, 13(1), 89. https://doi.org/10.3390/foods13010089
Hadjimbei, E., Botsaris, G., & Chrysostomou, S. (2022).
Beneficial effects of yoghurts and probiotic fermented
milks and their functional food potential. Foods, 11(17),
2691. https://doi.org/10.3390/foods11172691
Harat, S. G., & Pourjafar, H. (2025). Health benefits and
safety of postbiotics derived from different probiotic
species. Current Pharmaceutical Design, 31(2), 116–127.
https://doi.org/10.2174/011381612833541424082810522
9
Hijová, E. (2024). Postbiotics as metabolites and their
biotherapeutic potential. International Journal of
Molecular Sciences, 25(10), 5441.
https://doi.org/10.3390/ijms25105441
Homayouni Rad, A., Aghebati Maleki, L., Samadi Kafil,
H., Fathi Zavoshti, H., & Abbasi, A. (2020). Postbiotics
as novel health-promoting ingredients in functional foods.
Health Promotion Perspectives, 10(1), 3–4.
https://doi.org/10.15171/hpp.2020.02
Hoxha, R., Evstatieva, Y., & Nikolova, D. (2023).
Physicochemical, rheological, and sensory characteristics
of yogurt fermented by lactic acid bacteria with probiotic
potential and bioprotective properties. Foods, 12(13),
2552. https://doi.org/10.3390/foods12132552
Ibrahim, S. A., Ayivi, R. D., Zimmerman, T., Siddiqui, S.
A., Altemimi, A. B., Fidan, H., Esatbeyoglu, T., &
Bakhshayesh, R. V. (2021). Lactic acid bacteria as
antimicrobial agents: Food safety and microbial food
spoilage prevention. Foods, 10(12), 3131.
https://doi.org/10.3390/foods10123131
Isaac-Bamgboye, F. J., Mgbechidinma, C. L., Onyeaka, H.,
Isaac-Bamgboye, I. T., & Chukwugozie, D. C. (2024).
Exploring the potential of postbiotics for food safety and
human health improvement. Journal of Nutrition and
Metabolism, 2024, 1868161.
https://doi.org/10.1155/2024/1868161
Jahedi, S., & Pashangeh, S. (2025). Bioactivities of
postbiotics in food applications: A review. Iranian
Journal of Microbiology, 17(3), 348–357.
https://doi.org/10.18502/ijm.v17i3.18816
Ji, J., Jin, W., Liu, S. J., Jiao, Z., & Li, X. (2023).
Probiotics, prebiotics, and postbiotics in health and
disease. MedComm, 4(6), e420.
https://doi.org/10.1002/mco2.420
Liang, B., & Xing, D. (2023). The current and future
perspectives of postbiotics. Probiotics and Antimicrobial
Proteins, 15(6), 1626–1643.
https://doi.org/10.1007/s12602-023-10045-x
Ma, L., Tu, H., & Chen, T. (2023). Postbiotics in human
health: A narrative review. Nutrients, 15(2), 291.
https://doi.org/10.3390/nu15020291
Meybodi, N. M., Mortazavian, A. M., Arab, M., &
Nematollahi, A. (2020). Probiotic viability in yoghurt: A
review of influential factors. International Dairy Journal,
109, 104793.
https://doi.org/10.1016/j.idairyj.2020.104793
Molina, D., Marinas, I. C., Angamarca, E., Hanganu, A.,
Stan, M., Chifiriuc, M. C., & Tenea, G. N. (2025).
Postbiotic-based extracts from native probiotic strains: A
promising strategy for food preservation and
antimicrobial defense. Antibiotics, 14(3), 318.
https://doi.org/10.3390/antibiotics14030318
Moradi, M., Kousheh, S. A., Almasi, H., Alizadeh, A.,
Guimarães, J. T., Yılmaz, N., & Lotfi, A. (2020).
Postbiotics produced by lactic acid bacteria: The next
frontier in food safety. Comprehensive Reviews in Food
Science and Food Safety, 19(6), 3390–3415.
https://doi.org/10.1111/1541-4337.12623
Nakharuthai, C., Boonanuntanasarn, S., Kaewda, J., &
Manassila, P. (2023). Isolation of potential probiotic
Bacillus spp. from the intestine of Nile tilapia to construct
recombinant probiotic expressing CC chemokine and its
effectiveness on innate immune responses in Nile tilapia.
Animals, 13(6), 986. https://doi.org/10.3390/ani13060986
Pattapulavar, D. V., Ramanujam, S., Kini, B., &
Christopher, J. G. (2025). Probiotic-derived postbiotics:
A perspective on next-generation therapeutics. Frontiers
in Nutrition, 12, 1624539.
https://doi.org/10.3389/fnut.2025.1624539
Tong, Y., Abbas, Z., Zhang, J., Wang, J., Zhou, Y., Si, D.,
... & Zhang, R. (2025). Antimicrobial activity and
mechanism of novel postbiotics against foodborne
www.ijzab.com
Asefa, Z., Belay, A., Welelaw, E., & Haile, M. (2025).
Postbiotics and their biotherapeutic potential for chronic
disease and their feature perspective: A review. Frontiers
in Microbiomes, 4, 1489339.
https://doi.org/10.3389/frmbi.2025.1489339
Bhardwaj, A., Puniya, M., Sangu, K. P. S., Kumar, S., &
Dhewa, T. (2012). Isolation and biochemical
characterization of Lactobacillus species isolated from
Dahi. Research & Reviews: A Journal of Dairy Science
and Technology, 1(2), 1–14.
Drumond, M. M., Tapia-Costa, A. P., Neumann, E., Nunes,
Á. C., Barbosa, J. W., Kassuha, D. E., & Mancha-Agresti,
P. (2023). Cell-free supernatant of probiotic bacteria
exerted antibiofilm and antibacterial activities against
Pseudomonas aeruginosa: A novel biotic therapy.
Frontiers in Pharmacology, 14, 1152588.
https://doi.org/10.3389/fphar.2023.1152588
Goa, T., Beyene, G., Mekonnen, M., & Gorems, K. (2022).
Isolation and characterization of lactic acid bacteria from
fermented milk produced in Jimma Town, Southwest
Ethiopia, and evaluation of their antimicrobial activity
against selected pathogenic bacteria. International
Journal of Food Science, 2022, 2076021.
https://doi.org/10.1155/2022/2076021
Gurunathan, S., Thangaraj, P., & Kim, J. H. (2023).
Postbiotics: Functional food materials and therapeutic
agents for cancer, diabetes, and inflammatory diseases.
Foods, 13(1), 89. https://doi.org/10.3390/foods13010089
Hadjimbei, E., Botsaris, G., & Chrysostomou, S. (2022).
Beneficial effects of yoghurts and probiotic fermented
milks and their functional food potential. Foods, 11(17),
2691. https://doi.org/10.3390/foods11172691
Harat, S. G., & Pourjafar, H. (2025). Health benefits and
safety of postbiotics derived from different probiotic
species. Current Pharmaceutical Design, 31(2), 116–127.
https://doi.org/10.2174/011381612833541424082810522
9
Hijová, E. (2024). Postbiotics as metabolites and their
biotherapeutic potential. International Journal of
Molecular Sciences, 25(10), 5441.
https://doi.org/10.3390/ijms25105441
Homayouni Rad, A., Aghebati Maleki, L., Samadi Kafil,
H., Fathi Zavoshti, H., & Abbasi, A. (2020). Postbiotics
as novel health-promoting ingredients in functional foods.
Health Promotion Perspectives, 10(1), 3–4.
https://doi.org/10.15171/hpp.2020.02
Hoxha, R., Evstatieva, Y., & Nikolova, D. (2023).
Physicochemical, rheological, and sensory characteristics
of yogurt fermented by lactic acid bacteria with probiotic
potential and bioprotective properties. Foods, 12(13),
2552. https://doi.org/10.3390/foods12132552
Ibrahim, S. A., Ayivi, R. D., Zimmerman, T., Siddiqui, S.
A., Altemimi, A. B., Fidan, H., Esatbeyoglu, T., &
Bakhshayesh, R. V. (2021). Lactic acid bacteria as
antimicrobial agents: Food safety and microbial food
spoilage prevention. Foods, 10(12), 3131.
https://doi.org/10.3390/foods10123131
Isaac-Bamgboye, F. J., Mgbechidinma, C. L., Onyeaka, H.,
Isaac-Bamgboye, I. T., & Chukwugozie, D. C. (2024).
Exploring the potential of postbiotics for food safety and
human health improvement. Journal of Nutrition and
Metabolism, 2024, 1868161.
https://doi.org/10.1155/2024/1868161
Jahedi, S., & Pashangeh, S. (2025). Bioactivities of
postbiotics in food applications: A review. Iranian
Journal of Microbiology, 17(3), 348–357.
https://doi.org/10.18502/ijm.v17i3.18816
Ji, J., Jin, W., Liu, S. J., Jiao, Z., & Li, X. (2023).
Probiotics, prebiotics, and postbiotics in health and
disease. MedComm, 4(6), e420.
https://doi.org/10.1002/mco2.420
Liang, B., & Xing, D. (2023). The current and future
perspectives of postbiotics. Probiotics and Antimicrobial
Proteins, 15(6), 1626–1643.
https://doi.org/10.1007/s12602-023-10045-x
Ma, L., Tu, H., & Chen, T. (2023). Postbiotics in human
health: A narrative review. Nutrients, 15(2), 291.
https://doi.org/10.3390/nu15020291
Meybodi, N. M., Mortazavian, A. M., Arab, M., &
Nematollahi, A. (2020). Probiotic viability in yoghurt: A
review of influential factors. International Dairy Journal,
109, 104793.
https://doi.org/10.1016/j.idairyj.2020.104793
Molina, D., Marinas, I. C., Angamarca, E., Hanganu, A.,
Stan, M., Chifiriuc, M. C., & Tenea, G. N. (2025).
Postbiotic-based extracts from native probiotic strains: A
promising strategy for food preservation and
antimicrobial defense. Antibiotics, 14(3), 318.
https://doi.org/10.3390/antibiotics14030318
Moradi, M., Kousheh, S. A., Almasi, H., Alizadeh, A.,
Guimarães, J. T., Yılmaz, N., & Lotfi, A. (2020).
Postbiotics produced by lactic acid bacteria: The next
frontier in food safety. Comprehensive Reviews in Food
Science and Food Safety, 19(6), 3390–3415.
https://doi.org/10.1111/1541-4337.12623
Nakharuthai, C., Boonanuntanasarn, S., Kaewda, J., &
Manassila, P. (2023). Isolation of potential probiotic
Bacillus spp. from the intestine of Nile tilapia to construct
recombinant probiotic expressing CC chemokine and its
effectiveness on innate immune responses in Nile tilapia.
Animals, 13(6), 986. https://doi.org/10.3390/ani13060986
Pattapulavar, D. V., Ramanujam, S., Kini, B., &
Christopher, J. G. (2025). Probiotic-derived postbiotics:
A perspective on next-generation therapeutics. Frontiers
in Nutrition, 12, 1624539.
https://doi.org/10.3389/fnut.2025.1624539
Tong, Y., Abbas, Z., Zhang, J., Wang, J., Zhou, Y., Si, D.,
... & Zhang, R. (2025). Antimicrobial activity and
mechanism of novel postbiotics against foodborne
Arunavarsini Kumarasamy and R Mahenthiran Int. J. Zool. Appl. Biosci., 10(5), 83-88, 2025
www.ijzab.com
pathogens. LWT, 217, 117464.
https://doi.org/10.1016/j.lwt.2025.117464
Vargas-González, A., Barajas, M., & Pérez-Sánchez, T.
(2024). Isolation of lactic acid bacteria (LAB) from
salmonids for potential use as probiotics: In vitro assays
and toxicity assessment of Salmo trutta embryonated
eggs. Animals, 14(2), 200.
https://doi.org/10.3390/ani14020200.
Yadav, A., Jaiswal, P., Jaiswal, M., Kumar, N., Sharma, R.,
Raghuwanshi, S., & Bisen, P. S. (2015). Concise review:
Importance of probiotics yogurt for human health
improvement. IOSR Journal of Environmental Science,
Toxicology and Food Technology, 9(7), 25–30.
https://doi.org/10.9790/2402-09712530.
www.ijzab.com
pathogens. LWT, 217, 117464.
https://doi.org/10.1016/j.lwt.2025.117464
Vargas-González, A., Barajas, M., & Pérez-Sánchez, T.
(2024). Isolation of lactic acid bacteria (LAB) from
salmonids for potential use as probiotics: In vitro assays
and toxicity assessment of Salmo trutta embryonated
eggs. Animals, 14(2), 200.
https://doi.org/10.3390/ani14020200.
Yadav, A., Jaiswal, P., Jaiswal, M., Kumar, N., Sharma, R.,
Raghuwanshi, S., & Bisen, P. S. (2015). Concise review:
Importance of probiotics yogurt for human health
improvement. IOSR Journal of Environmental Science,
Toxicology and Food Technology, 9(7), 25–30.
https://doi.org/10.9790/2402-09712530.