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This study aims to determine the antibiofilm effect of cell-free supernatant (CFS) of Lactobacillus brevis strains against Streptococcus mutans strains. To study the antibiofilm mechanism against S. mutans strains, antibacterial effects, cell surface properties (auto-aggregation and cell surface hydrophobicity), exopolysaccharide (EPS) production, and morphological changes were examined. The antibiofilm effect of L. brevis KCCM 202399 CFS as morphological changes were evaluated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM), compared with the control treatment. Among the L. brevis strains, L. brevis KCCM 202399 showed the highest antibiofilm effect on S. mutans KCTC 5458. The antibacterial effect of L. brevis KCCM 202399 against S. mutans KCTC 5458 was investigated using the deferred method (16.00 mm). The minimum inhibitory concentration of L. brevis KCCM 202399 against S. mutans KCTC 5458 was 25.00%. Compared with the control treatment, L. brevis KCCM 202399 CFS inhibited the bacterial adhesion of S. mutans KCTC 5458 by decreasing auto-aggregation, cell surface hydrophobicity, and EPS production (45.91%, 40.51%, and 67.44%, respectively). L. brevis KCCM 202399 CFS inhibited and eradicated the S. mutans KCTC 5458 biofilm. Therefore, these results suggest that L. brevis KCCM 202399 CFS may be used to develop oral health in the probiotic industry.

This study was carried out to characterize antioxidant activity, total phenolic content, and the phenolic and flavonoids profile of postbiotic of Pediococcus acidilactici and to evaluate the effects of postbiotics (10% and 50%) alone and in combination with chitosan coating (1%) on the microbial and chemical quality of chicken breast fillets during storage at 4 °C. Antioxidant activity and total phenolic content of the postbiotics were found to be 1291.02 ± 1.5 mg/L TEAC and 2336.11 ± 2.36 mg/L GAE, respectively. The most abundant phenolic was vanillic acid, followed by t-caffeic, gallic, and caftaric acids. The postbiotic-chitosan (50% + 1%) combination decreased L. monocytogenes and S. Typhimurium counts by 1.5 and 2.1 log10 CFU/g, respectively, compared to the control (P 0.05). Postbiotic treatment did not significantly change the pH values and color properties of the breast fillets (P > 0.05). Postbiotic-chitosan combinations extended the shelf-life by up to 12 days compared to the control. In conclusion, the postbiotic-chitosan combination can be used to preserve and improve the microbial quality of chicken meat products.

Staphylococcus aureus is one of the most common microorganisms and causes foodborne diseases. In particular, biofilm-forming S. aureus is more resistant to antimicrobial agents and sanitizing treatments than planktonic cells. Therefore, this study aimed to investigate the anti-biofilm effects of cell-free supernatant (CFS) of Saccharomyces cerevisiae isolated from cucumber jangajji compared to grapefruit seed extract (GSE). CFS and GSE inhibited and degraded S. aureus biofilms. The adhesion ability, auto-aggregation, and exopolysaccharide production of CFS-treated S. aureus, compared to those of the control, were significantly decreased. Moreover, biofilm-related gene expression was altered upon CFS treatment. Scanning electron microscopy images confirmed that CFS exerted anti-biofilm effects against S. aureus. Therefore, these results suggest that S. cerevisiae CFS has anti-biofilm potential against S. aureus strains.

Bacillus amyloliquefaciens LZN01 shows antagonistic behaviour against Fusarium oxysporum f. sp. niveum (Fon). This study aimed to analyze the antifungal activity and the functional components of cell-free supernatant from B. amyloliquefaciens LZN01 that inhibited Fon growth. The results showed that the cell-free supernatant (CFS) from the death phase had stronger antifungal activity against Fon compared to those from the exponential stage and stationary phase. The analyses from scanning and transmission electron microscopy demonstrated that treatment with CFS led to cellular morphological changes, including concave formations on the conidial surface, the disruption of cell walls and membranes, the leakage of intracellular contents and the aggregation of organelles. Confocal laser scanning microscopy revealed that the CFS damaged membrane integrity. Myriocin, sphingofungin E, sphingofungin F, 3-methyl-2-oxovaleric acid, gabapentin and sphingofungin C were confirmed as the major differential metabolites by ultra-high-performance liquid chromatography-LTQ orbitrap (UHPLC-LTQ Orbitrap) MS analysis. Quantitative analysis showed that the myriocin content in the CFS was 0.6 μg/mL, and its minimum inhibitory concentration (MIC) was 1.25 μg/mL. It can be speculated that some antifungal compounds in the CFS, including myriocin, sphingofungin E, sphingofungin F and sphingofungin C, play major roles in inhibiting the growth of Fon and the synergistic effects among these antifungal compounds are important in suppressing Fon reproduction. This study suggests that B. amyloliquefaciens LZN01 is a promising biological agent against Fon as its CFS exerts antifungal activity by deforming conidial structures and damaging membranes and myriocin was one of the major functional components of the CFS.

The rhizosphere soil of medicinal plants is rich in microorganisms that develop antibiotics as natural mechanism of protection against other microbes that live in their vicinity. The present study aims to explore the production of antibacterial agents from rhizosphere soil bacteria of 11 medicinal plants and determine their activity against Gram-negative (Pseudomonas aeruginosa, Escherichia coli) and Gram-positive (Bacillus cereus, Staphylococcus aureus) bacteria. Soil samples were collected and used to isolate antibiotic producing bacteria (APB). Those isolates (108) were first tested using Cross-streak method against test bacteria. Then, isolates that showed a positive antibacterial effect (12) were tested by antibiotic susceptibility test (AST) of their cell free supernatant (CFS) and their extracellular and intracellular secondary metabolites extraction which gave positive results. Staphylococcus aureus found to be the most sensitive test bacteria with inhibitory zones ranging from 13.5 - 19 mm. Moreover, combinatorial effect of isolates CFS with two organic acids (3% Acetic acid and 0.4 mg/ml Acetylsalicylic acid), two commercial antibiotics (0.016 mg/ml Augmentin and 0.128 mg/ml Doxycycline), and two pure antibiotics (10 mcg/disk Penicillin and 25mcg/disk Carbenicillin) was in vitro evaluated using AST. The combinations of CFS-carbenicillin showed a marked synergistic activity against all test bacteria. The presence of possible antibacterial agents as acetic acid, lactic acid and citric acid in CFS of APB was confirmed by HPLC analysis. Ultimately, in vitro antibacterial study for rhizosphere soil bacteria in this work suggests the possibility of using these bacterial metabolites in clinical infections caused by selected test bacteria, especially when they combine with antibiotics or organic acids.

Antibacterial and antioxidative effects of microencapsulated Lactobacillus reuteri ATCC 55730 cell-free supernatant (CFS) alone (MCFS) or in combination with propolis water (MPW) and ethanolic extract (MPE) on sardine burger were investigated at 4 ± 1 °C for 15 days. Morphological properties of microcapsules were determined by scanning electron microscopy (SEM). Microcapsules had rough cylindrical structure and wrinkled morphology (especially the microcapsules with aqueous propolis extract). The use of microcapsules with propolis extracts maintained the sensory quality of sardine burgers. MCFS, MPW and MPE groups had 3 days longer sensorial shelf life although burgers with propolis extract (MPW and MPE groups) were more preferred by panellists. MCFS, MPW and MPE groups had a lower content of TVB-N than control. CFS from L. reuteri and propolis combinations in microencapsulation showed stronger antioxidative effect for fish burger. The highest TBA and FFA values were observed for the control (10.78 MDA/kg vs 12.98% oleic acid) and MCFS (10.67 MDA/kg vs 12.51% oleic acid) at the end of storage. Microbiological upper limit of 7 log cfu/g did not exceed for all groups during storage. Microencapsulated CFS from L. reuteri and mainly propolis water extract combinations induced a lower bacterial growth in fish burger. The results revealed that the use of Lactobacilli supernatant alone has a weak antioxidative effect whereas the microcapsules with propolis extract have the potential to be used as antioxidant, by enhancing quality characteristics of burger.

In this study, a composite film was prepared with bacterial cellulose (BC) of Gluconacetobacter xylinus and cell-free supernatant (CFS) of Enterococcus faecium TJUQ1, which was named BC-E. The optimum conditions for the preparation of the composite film with a minimal antibacterial activity were the soak of BC in 80 AU/mL CFS for 6 h. By scanning electron microscope observation, the surface network structure of BC-E was denser than that of BC. The tensile strength of BC and BC-E was 4.65 ± 0.88 MPa and 16.30 ± 0.92 MPa, the elongation at break of BC and BC-E was 3.33 ± 0.89% and 31.60 ± 1.15%, respectively, indicating the mechanical properties of BC-E were significantly higher than that of BC (P 0.05). The swelling ratio of BC-E (456.67 ± 7.20%) was lower than that of BC (1377.78 ± 9.07%), demonstrating BC-E films presented better water resistance. BC-E films were soaked with 320 AU/mL CFS, and then used to pack the ground meat with 6.55 log

The objective of this study was to evaluate the effect of cell-free supernatant (CFS) from Aeromonas sobria on the growth and spoilage potential of Shewanella putrefaciens in Pacific white shrimp (Litopenaeus vannamei) during cold chain logistics, including transportation, retailing, and domestic storage. It was shown that the quality of shrimps deteriorated in the cold chain logistics over time. The temperature fluctuation during the experimental period favored the growth of S. putrefaciens, increased the total volatile basic nitrogen (TVB-N) and biogenic amine value, and decreased the sensory quality of shrimps. The application of CFS resulted in the decline on the growth of S. putrefaciens after the early stationary phase stored at a cold condition. It is concluded that the application of CFS can inhibit microbial growth and the spoilage potential of S. putrefaciens and offset the quality deterioration of shrimp exposed to temperature fluctuation during cold chain logistics.

Postbiotics may be defined as soluble metabolites released by food-grade microorganisms during the growth and fermentation in complex microbiological culture, food or gut. It is rich in high and low molecular weight biologically active metabolites. There are still gaps concerning these substances, mainly how to use them for food applications. Although the most recent work on preparation and application of postbiotics from several probiotics are very encouraging, the suitability of postbiotics to combat microorganisms that deal with food safety should be tested mainly by analyzing the chemical composition and conducting antagonistic tests. Consequently, foods can effectively benefit from an identified postbiotic with a defined effect. This review approached the recent advances in relation to the preparation of postbiotics from lactic acid bacteria. The function of different instrumental analysis techniques and factors affecting the chemical composition of postbiotics were also comprehensively reviewed.

Biosynthesis of gold nanoparticles was investigated using Aspergillus flavus and the procedure was optimized for maximum production. The color changing from whitish-yellow to purple along with the maximum absorbance at 540 nm in UV-vis spectrum approved the production of gold nanoparticles preliminarily. The XRD spectrum of nanoparticles showed 2θ values corresponding to the gold nanocrystals. TEM micrographs demonstrated the extracellular formation of spherical gold nanoparticles. The optimization process revealed that the maximum rate of gold nanoparticles production achieved after 6 h at 28°C, 2.5 mM HAuCl4 concentration, and pH 6 with different shapes in the size range of 30–50 nm.

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 and 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 &lt, 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.

casein content. CaCl2 and CoCl2 were found to enhance the proteolytic activity at 1mM, while CuSO4 and FeSO4 were found to be needed in fewer amounts at 0.5mM and 0.1mM, respectively. The antibacterial activity of these bioactive peptides produced in the cell free supernatant was investigated against some human pathogenic bacteria. It was found that it impose a high antibacterial capacity on tested pathogens reaching 89% inhibition.

This study was undertaken to characterize a lactic acid bacterium 4I1, isolated from the freshwater fish, Zacco koreanus. Morphological, biochemical, and molecular characterization of 4I1 revealed it to be Pediococcus pentosaceus 4I1. The cell free supernatant (CFS) of P. pentosaceus 4I1 exhibited significant (p < 0.05) antibacterial effects (inhibition zone diameters: 16.5–20.4 mm) against tested foodborne pathogenic bacteria with MIC and MBC values of 250–500 and 500–1,000 μg/mL, respectively. Further, antibacterial action of CFS of P. pentosaceus 4I1 against two selected bacteria Staphylococcus aureus KCTC-1621 and Escherichia coli O157:H7 was determined in subsequent assays. The CFS of P. pentosaceus 4I1 revealed its antibacterial action against S. aureus KCTC-1621 and E. coli O157:H7 on membrane integrity as confirmed by a reduction in cell viability, increased potassium ion release (900 and 800 mmol/L), reduced absorption at 260-nm (3.99 and 3.77 OD), and increased relative electrical conductivity (9.9 and 9.7%), respectively. Gas chromatography–mass spectrometry (GC–MS) analysis of the CFS of P. pentosaceus 4I1 resulted in the identification of seven major compounds, which included amino acids, fatty acids and organic acids. Scanning electron microscopic-based morphological analysis further confirmed the antibacterial effect of CFS of P. pentosaceus 4I1 against S. aureus KCTC-1621 and E. coli O157:H7. In addition, the CFS of P. Pentosaceus 4I1 displayed potent inhibitory effects on biofilms formation by S. aureus KCTC-1621 and E. coli O157:H7. The study indicates the CFS of P. pentosaceus 4I1 offers an alternative means of controlling foodborne pathogens.

Using polystyrene surfaces for attachment, we evaluated biofilm formation and cell surface hydrophobicities of 17 Salmonella enterica strains (belonging to 9 different serovars), and further assessed the effect of cell-free culture supernatants (CFS) from Pseudomonas aeruginosa (containing acylated homoserine lactones (AHLs)), on the growth and biofilm development of S. enterica. The results indicated that most of the 17 strains readily formed biofilms on polystyrene surfaces, but the development of biofilms were significantly influenced by serovars and incubation conditions. Strains of S1 (S. London), S2 (S. London), S9 (S. Indiana) and S16 (S. Typhimurium) produced greater biofilms regardless of the tested conditions compared with other strains, with maximum biofilm production of 3.08, 2.47, 2.21 and 3.39 (crystal violet assay), respectively. Significant differences in cell hydrophobicity were observed between strains, S16 (S. Typhimurium) showed highest hydrophobicity values (>56%) compared with the other strains (

The conventional method of synthesizing gold nanoparticles (Au NPs) by chemical methods tends to cause an environmental concern; therefore there is an increasing tendency to use safe and nontoxic methods. The aim of the present study was to evaluate the anti-dermatophytic potential of biologically synthesized Au NPs using the cell free supernatant of Streptomyces sp. VITDDK3. The synthesized Au NPs were characterized using UV–visible spectra at 550 nm. XRD pattern analysis revealed peaks at 38.10° (111), 44.28° (200), 64.42° (220) and 77.37° (311) corresponding to the diffraction facets of Au. SEM analysis showed that the Au NPs were cubical in shape with an average size of 90 nm. The synthesized Au NPs were tested by the well diffusion method for antifungal activity (zones of inhibition) against Microphyton gypseum (10±0.47 mm) and Trichophyton rubrum (13±1.03 mm).

Biogenic principles to nanotechnology have generated tremendous attention in recent past owing eco friendly benign process for synthesis of nanoparticles. Present investigation reports extracellular synthesis of gold nanoparticles using cell free supernatant of Pseudomonas veronii AS 41G, a novel endophyte isolated from Annona squamosa L. Gold nanoparticles formation was confirmed with UV–Visible spectrophotometer. FTIR analysis predicted various functional groups responsible for reduction of metal salts and stabilization of gold nanoparticles. Nanoparticles were crystalline in nature as shown in XRD pattern. TEM analysis revealed morphological characteristics of nanoparticles with different size. Thus the present study attributes for facile process for synthesis of gold nanoparticles as an alternative for conventional methods. The study also highlights the new role of novel bacterium Pseudomonas veronii AS41G which will be very valuable as a record for the researchers working on it.

This work was conducted to evaluate the antilisterial activity of sakacin Q produced by Lactobacillus curvatus ACU-1 on the surface of cooked pork meat. A genetic re-characterization of the producer strain and a study of the structural genes involved in bacteriocin production were carried out as complementary data. Studies indicated that the bacteriocin was not attached to the producer cells favoring pre-purifications steps. Bacteriocin effectiveness was not compromised by adsorption to meat and fat tissues. Several ways of dispensing the bacteriocin onto the meat surface, namely cell culture, cell free supernatant (CFS), a mixture of both and freeze-dried reconstituted CFS, were investigated. The use of the latter was the most effective one to control Listeria growth within studied systems. L. curvatus ACU-1 and its bacteriocin presented promising technological characteristics that made them suitable for meat biopreservation. Fil: Rivas, Franco Paolo. Universidad Nacional del Chaco Austral. Departamento de Ciencias Basicas y Aplicadas. Laboratorio de Microbiologia de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Castro, Marcela Paola. Universidad Nacional del Chaco Austral. Departamento de Ciencias Basicas y Aplicadas. Laboratorio de Microbiologia de Alimentos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Vallejo, Marisol. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Trelew; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Marguet, Emilio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina Fil: Campos, Carmen Adriana. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

In this work, 100 samples each of 'ugba' and 'okpiye' were evaluated for the presence of bacteriocin producing lactic acid bacteria. Thirty strains showing antibacterial activity against at least one of the indicator organisms were selected from a total of 752 colonies isolated from the condiments. Out of the 30, only five strains retained activity after the pH of the broth supernatant was adjusted to 6.5. When evaluated by the agar-well diffusion assay, the spectra of inhibitory activity showed that Staphylococcus aureus was the most sensitive indicator organism tested, while Listeria monocytogenes was the most resistant. One strain (UG 2) was active against Escherichia coli. The assays using the cell-free supernatant of the cultures showed that the bacteriocins were completely inactivated by the proteolyses as well as by the chloroform treatment. In ethanol, the activity of the compounds was only partially modified. When incubated in a water bath at 80°C for 30 min, no significant activity loss was recorded. The antimicrobial activity of the bacteriocins produced by the lactic acid bacteria has potential for use in biopreservation of condiments against the spoilage and food - borne pathogens.

Enterococcus faecalis DBFIQ E24 strain produces antimicrobial substances that inhibit the growth offood-borne pathogenic bacteria, yeasts and moulds. This broad antimicrobial spectrum was determined by obtaining the cell-free supernatant (CFS) and employing the agar-well-diffusion method. Its antibacterial activity was completely inactivated by the action of proteinase K and not affected by catalase action. Besides, it was stable to thermal treatments, showing maximum antibacterial activity at pH 7.0. Moreover, CFS showed a bactericidal effect against Escherichia coli DBFIQ Ec9 strain. All these interesting physicochemical properties allow that either CFS or E. faecalis DBFIQ E24 strain to be considered as potential food biopreservatives. Fil: Cardoso, Maria de Las Mercedes. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina Fil: Manzo, Ricardo Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina Fil: Tonarelli, Georgina Guadalupe. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentina Fil: Simonetta, Arturo Carlos. Universidad Nacional del Litoral. Facultad de Ingeniería Química; Argentina

Aggregation factors isolated from the cell surface of five species of sponge are shown to be specific in their ability to enhance cell aggregation. Factors from Haliclona viridis, Haliclona variabilis, Tedania ignis, Homaxinella rudis, and Dysidea crawshayi each exhibit the species specific enhancing effect and have no such effect in heterospecific cell-factor combinations. Radioactively labeled cell free supernatant materials are shown to bind selectively to homospecific cells suggesting that cells contain specific receptors for attachment of the aggregation mediating materials. Finally, in several heterospecific combinations there was an inhibition of cell aggregation. The inhibitory agent was separated from the enhancing factor chromatographically. After removal of the inhibitory substance, the enhancing factor was still active in promoting cell aggregation of the homospecific cells only.

The role of different fractions of rumen contents in the hydrolysis of trilinolein and the subsequent hydrogenation of the linoleic acid has been investigated by a series of in vitro incubations. Hydrolysis of the trilinolein to free linoleic acid occurs almost wholly in the cell-free supernatant; the liberated linoleic acid in the supernatant can be rapidly adsorbed onto food particles where it is hydrogenated to stearic acid via the C18 trans-11 monoene. Some 25% of the trilinolein added as substrate was taken up by the bacteria and of this a small percentage appeared to be hydrolysed and the free linoleic acid hydrogenated to stearic acid intracellularly. No conclusive evidence was obtained to suggest that this intracellular hydrogenation proceeded by a route other than that which took place on the food particles.