Biosorption of silver cations onto Lactococcus lactis and Lactobacillus casei isolated from dairy products

Comparative Account of Biogenic Synthesis of Silver Nanoparticles Using Probiotics and Their Antimicrobial Activity Against Challenging Pathogens

The present work focusses on development of a safe, inexpensive, and more accessible source for biosynthesis of silver nanoparticles. Four different in-house probiotic isolates, i.e., Lactobacillus pentosus S6, Lactobacillus plantarum F22, Lactobacillus crustorum F11, and Lactobacillus paraplantarum KM1 isolated from different food sources, were used in the current study to check their ability to synthesize silver nanoparticles. All the probiotic-synthesized silver nanoparticles show maximum surface plasmon resonance (SPR) at a peak of 450 nm, which confirms the formation of silver nanoparticles. Scanning electron microscopy (SEM) analysis identified the shape and distribution of silver nanoparticles. Transmission electron microscopy (TEM) revealed the average size of synthesized nanoparticles in the range of 10–50 nm, with the smallest size of 5 nm for silver nanoparticles synthesized by L. crustorum F11. Further, Fourier-transform infrared spectroscopy (FTIR) detected the presence of different functional groups responsible for reduction of silver ion to form silver nanoparticles. The antimicrobial activity of these AgNPs was also found to be effective against different bacterial and fungal pathogens, viz., antibiotic-resistant Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Pythium aphanidermatum, Fusarium oxysporum, and Phytopthora parasitica. However, L. crustorum F11–synthesized AgNP showed maximum inhibition against all the bacterial and fungal pathogens, with highest against S. aureus (20 ± 0.61 mm) and F. oxysporum (23 ± 0.37). Findings from this study provide a durable and eco-friendly method for the biosynthesis of silver nanoparticles, having strong antimicrobial activity against different multidrug-resistant microorganisms.

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New sources of lactic acid bacteria with potential antibacterial properties

In the face of the growing demand for functional food, the search for new sources of lactic acid bacteria (LAB) becomes a priority. In our research, we used multiplied culture conditions followed by identification via the matrix-assisted laser desorption ionization-time of flight mass spectrometry for seeking LAB strains in plant- and animal-derived sources. Furthermore, the selected LAB isolates were examined for their proteolytic activity as well as antimicrobial action against different bacterial pathogens. The applied method appeared to be useful tool for searching LAB strains within different types of the biological matrices. The best source of the LABs was from calf. Comparing properties of the two selected LABs, those isolated from calf demonstrated the greatest proteolytic and antibacterial properties suggesting that gastrointestinal microbiota are the most valuable LAB source. Nevertheless, second selected strain derived from pickled cucumber juice may be also treated as a promising source of potential probiotic strains.

Problems with identifying and distinguishing salivary streptococci: a multi-instrumental approach

Aim: The purpose of this study was to create an alternative protocol for the DNA-based identification of salivary microbiota focused on the distinguishing of Streptococcus species. Materials & methods: Salivary bacteria were identified using 16S rDNA sequencing and proteins and lipids profiling using MALDI-TOF/MS as well as FTIR analysis. Results: Most of the isolates belonged to streptococci - mostly the salivarious group indistinguishable by the molecular technique. In turn, MALDI analysis allowed for their fast and reliable classification. Although FTIR spectroscopy demonstrated the correct species classification, the spectra interpretation was time consuming and complicated. Conclusion: MALDI-TOF/MS demonstrated the biggest effectiveness in the identification and discrimination between the salivary streptococci, which could be easily incorporated in the workflow of routine microbiological laboratories.

The study of the molecular mechanism of Lactobacillus paracasei clumping via divalent metal ions by electrophoretic separation

In this work, the molecular mechanism of Lactobacillus paracasei bio-colloid clumping under divalent metal ions treatment such as zinc, copper and magnesium at constant concentrations was studied. The work involved experimental (electrophoretic - capillary electrophoresis in pseudo-isotachophoresis mode, spectroscopic and spectrometric - FT-IR and MALDI-TOF-MS, microscopic - fluorescent microscopy, and flow cytometry) and theoretical (DFT calculations of model complex systems) characterization. Electrophoretic results have pointed out the formation of aggregates under the Zn²⁺ and Cu²⁺ modification, whereas the use of the Mg²⁺ allowed focusing the zone of L. paracasei biocolloid. According to the FT-IR analysis, the major functional groups involved in the aggregation are deprotonated carboxyl and amide groups derived from the bacterial surface structure. Nature of the divalent metal ions was shown to be one of the key factors influencing the bacterial aggregation process. Proteomic analysis showed that surface modification had a considerable impact on bacteria molecular profiles and protein expression, mainly linked to the activation of carbohydrate and nucleotides metabolism as well with the transcription regulation and membrane transport. Density-functional theory (DFT) calculations of modeled Cu²⁺, Mg²⁺ and Zn²⁺ coordination complexes support the interaction between the divalent metal ions and bacterial proteins. Consequently, the possible mechanism of the aggregation phenomenon was proposed. Therefore, this comprehensive study could be further applied in evaluation of biocolloid aggregation under different types of metal ions.

Mixed culture of Lactococcus lactis and Kluyveromyces marxianus isolated from kefir grains for pollutants load removal from Jebel Chakir leachate

The wastewater from the dumping site usually contains high pollutant levels. Biological process and physico-chemical treatments are among several technologies for wastewater treatment. Using microorganisms in the treatment of landfill leachate is an emerging research issue. Furthermore, bioremediation is a feasible approach for pollutants removal from landfill leachate which would provide an efficient way to resolve the issue of landfill leachate. In this study, the performance of yeast and bacteria isolated from kefir grains was assessed for landfill leachate treatment. Kefir grains microbial composition was evaluated by molecular approaches (Rep-PCR and 16S rRNA gene sequencing). The obtained outcomes denoted that high concentrations of lactic acid bacteria and yeast populations (over 10⁷  CFU/ml) were found in the kefir grains and were essentially composed of Lactococcus lactis, Lactobaccillus kefirien, bacillus sp., L. lactis, and Kluyveromyces marxianus. The co-culture with 1% of inoculum size was demonstrated as the most efficient in the degradation of different contaminants. The overall abatement rate of chemical oxygen demand (COD), ammonium nitrogen ( NH 4 + - N ), and salinity were 75.8%, 85.9%, and 75.13%, respectively. The bioremediation process resulted in up of 75% removal efficiency of Ni and Cd, and a 73.45%, 68.53%, and a 58.17% removal rates of Cu, Pb, and Fe, respectively. The research findings indicate the performance of L. lactis and K. marxianus co-culture isolated from kefir grains for the bioremediation of LFL. PRACTITIONER POINTS: Isolation and identification of microorganisms from kefir grains was carried out. Biological treatment of LFL using monoculture of (Lactoccocus lactis; Kluyveromyces marxianus) and co-culture (5% of L. lactis and 5% K. marxianus) has been performed. Biological treatment using co-culture strain is an effective approach to remove organic matter, NH 4 + - N and heavy metals.

Zinc Oxide Nanocomposites-Extracellular Synthesis, Physicochemical Characterization and Antibacterial Potential

This research presents, for the first time, the potential of the Lactobacillus paracasei LC20 isolated from sweet whey as a novel, effective and accessible source for post-cultured ZnO nanocomposites synthesis. The obtained nanocomposites were subjected to comprehensive characterization by a broad spectrum of instrumental techniques. Results of spectroscopic and microscopic analysis confirmed the hexagonal crystalline structure of ZnO in the nanometer size. The dispersion stability of the obtained nanocomposites was determined based on the zeta potential (ZP) measurements-the average ZP value was found to be -29.15 ± 1.05 mV in the 7-9 pH range. The ZnO nanocomposites (NCs) demonstrated thermal stability up to 130 °C based on the results of thermogravimetric TGA/DTG) analysis. The organic deposit on the nanoparticle surface was recorded by spectroscopic analysis in the infrared range (FT-IR). Results of the spectrometric study exhibited nanostructure-assisted laser desorption/ionization effects and also pointed out the presence of organic deposits and, what is more, allowed us to identify the specific amino acids and peptides present on the ZnO NCs surfaces. In this context, mass spectrometry (MS) data confirmed the nano-ZnO formation mechanism. Moreover, fluorescence data showed an increase in fluorescence signal in the presence of nanocomposites designed for potential use as, e.g., biosensors. Despite ZnO NCs' luminescent properties, they can also act as promising antiseptic agents against clinically relevant pathogens. Therefore, a pilot study on the antibacterial activity of biologically synthesized ZnO NCs was carried out against four strains (Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa) by using MIC (minimal inhibitory concentration). Additionally, the colony forming units (CFU) assay was performed and quantified for all bacterial cells as the percentage of viable cells in comparison to a control sample (untreated culture) The nanocomposites were effective among three pathogens with MIC values in the range of 86.25-172.5 μg/mL and showed potential as a new type of, e.g., medical path or ointment formulation.

Tolerance and mycoremediation of silver ions by Fusarium solani

Silver ions discharged from various industries, are potentially toxic to living organisms at low concentrations, thus, there is an increasing need for development of an eco-friendly and cost-effective approach for its bioremediation. Filamentous fungi especially, Fusarium solani displayed a strong resistance to copper and cadmium ions as revealed from our previous study (El-Sayed 2014), however, the mechanisms of silver resistance by this fungus has not been resolved yet. Thus, this study was an extension to our previous work, to elucidate the mechanism of silver ions resistance and biotransformation by F. solani. The growth, bioaccumulation, thiol, total antioxidant, malondialdehyde (MDA), hydrogen peroxide (H₂O₂) contents and polyphenol oxidase (PPO) and catalase (CAT) activities of F. solani in response to silver ions were determined. Production and bioaccumulation of silver nanoparticles was characterized by UV-visible spectroscopy, TEM, and X-ray powder diffraction (XRD). The ultrastructural changes of F. solani induced by Ag(I) was examined by TEM and SEM. Production of oxalic acid by F. solani was increased by about 343.8% in response to 400 mg/l Ag(I), compared to control cultures (without silver ions) as revealed from HPLC analysis. The maximum biosorption levels by the native and alkali-treated biomass were carried out at pH 5.0, initial metal concentration 200 mg/l, biomass 0.5 g/l, temperature 35 °C, and contact time 1 h (native biomass) and 3 h (alkali-treated biomass). Fourier transform infrared spectroscopy (FTIR) results revealed that the main functional groups involved on this mycoremediation were C–S stretching, C=O C=N, C – H bending, C–N stretching and N–H bending. EDX spectra indicated the involvement of fungal cellular sulfur and phosphorus compounds in Ag(I) binding.

Use of Lactobacillus paracasei strain for zearalenone binding and metabolization

The study investigated the zearalenone (ZEA) neutralization process as a consequence of metabolization and binding process by the probiotic bacterial strain Lactobacillus paracasei using high performance liquid chromatography (HPLC). In order to determine the nature of the binding process the kinetic and spectroscopic approach were used. Moreover, the influence of ZEA on L. paracasei metabolism was examined by the determination of the proteome profile of cells and the profile of volatile compounds (VOCs) produced by bacteria cells. For this purpose the Matrix-Assisted Laser Desorption/Ionization-Time of Flight mass spectrometry (MALDI-TOF MS) and headspace solid-phase microextraction coupled to gas chromatography/mass spectrometry (HS-SPME/GC-MS) techniques were used. The obtained results indicate that in the mechanism of ZEA neutralization both - metabolization/biotransformation and binding/biosorption processes are involved. Furthermore, the biotransformation of ZEA to both α- and β-ZOL with a predominance of β-ZOL by lactic acid bacteria strain was recorded. The results suggest that the tested microorganism can be used as a potential detoxification agent for grain and feed.

Investigation of Zearalenone Adsorption and Biotransformation by Microorganisms Cultured under Cellular Stress Conditions

The zearalenone binding and metabolization ability of probiotic microorganisms, such as lactic acid bacteria, Lactobacillus paracasei, Lactococcus lactis, and yeast Saccharomyces cerevisiae, isolated from food products, were examined. Moreover, the influence of cellular stress (induced by silver nanoparticles) and lyophilization on the effectiveness of tested microorganisms was also investigated. The concentration of zearalenone after a certain time of incubation with microorganisms was determined using high-performance liquid chromatography. The maximum sorption effectiveness for L. paracasei, L. lactis, and S. cerevisiae cultured in non-stress conditions was 53.3, 41.0, and 36.5%, respectively. At the same time for the same microorganisms cultured at cellular stress conditions, the maximum sorption effectiveness was improved to 55.3, 47.4, and 57.0%, respectively. Also, the effect of culture conditions on the morphology of the cells and its metabolism was examined using microscopic technique and matrix-assisted laser desorption ionization-time of flight mass spectrometry, respectively.

AggLr, a novel aggregation factor in Lactococcus raffinolactis BGTRK10-1: its role in surface adhesion

The ability of lactic acid bacteria to form multi-cellular aggregates via self-aggregation is regarded as an important mechanism for stress tolerance, adhesion, colonization and genetic material exchange. The novel aggLr gene encoding for the auto-aggregation promoting protein (AggLr) of Lactococcus raffinolactis BGTRK10-1 was cloned. Heterologous expression of AggLr enabled auto-aggregation, higher hydrophobicity and collagen and fibronectin binding of the carrier strains. Domain analysis and the type of aggregates formed by cells expressing AggLr confirmed that this aggregation factor belongs to the family of high molecular weight proteins that the authors propose to be called Snow-flake Forming Collagen Binding Aggregation Factors (SFCBAF). An additional feature of SFCBAF is that they are rich in threonine and lysine and are free of cysteine in all of the aggregation factors described so far. In contrast to previously discovered SFCBAF, the gene encoding for AggLr is located on the chromosome in the strain BGTRK10-1.

Heavy Metal Stress and Its Consequences on Exopolysaccharide (EPS)-Producing Pantoea agglomerans

Currently, the heavy metal pollution is of grave concern, and the part of microorganism for metal bioremediation should take into account as an efficient and economic strategy. On this framework, the heavy metal stress consequences on exopolysaccharide (EPS)-producing agricultural isolate, Pantoea agglomerans, were studied. The EPS production is a protective response to stress to survive and grow in the metal-contaminated environment. P. agglomerans show tolerance and mucoid growth in the presence of heavy metals, i.e., mercury, copper, silver, arsenic, lead, chromium, and cadmium. EDX first confirmed the metal accumulation and further, FTIR determined the functional groups involved in metal binding. The ICP-AES identified the location of cell-bound and intracellular metal accumulation. Metal deposition on cell surface has released more Ca²⁺. The effect on bacterial morphology investigated with SEM and TEM revealed the sites of metal accumulation, as well as possible structural changes. Each heavy metal caused distinct change and accumulated on cell-bound EPS with some intracellular deposits. The metal stress caused a decrease in total protein content and increased in total carbohydrate with a boost in EPS. Thus, the performance of P. agglomerans under metal stress indicated a potential candidate for metal bioremediation. Graphical Abstract ᅟ.

Microbiology neutralization of zearalenone using Lactococcus lactis and Bifidobacterium sp

The aim of the study was to neutralize zearalenone by lactic acid bacteria (LAB) such as Lactococcus lactis and Bifidobacterium sp. and investigate the mechanism of zearalenone (ZEA) binding. Neutralization of ZEA by LAB was confirmed by identification of binding kinetics and spectroscopic studies such as Fourier transform infrared spectroscopy (FT-IR) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The obtained results showed that the kinetic process of zearalenone binding to L. lactis is not homogeneous but is expressed with an initial rapid stage with about 90% of ZEA biosorption and with a much slower second step. In case of Bifidobacterium sp., the neutralization process is homogeneous; the main stage can be described with about 88% of ZEA biosorption. MALDI-TOF-MS measurements and FTIR analysis confirmed the uptake of zearalenone molecules by bacterial species. Moreover, the assessment of dead and live lactic acid bacteria cells after zearalenone treatment was performed using fluorescence microscopy. Graphical abstract Microbiology neutralization of zearalenone using Lactococcus lactis and Bifidobacterium sp. was confirmed by identification of binding kinetics and spectroscopic studies such as FT-IR spectroscopy and MALDI-TOF-MS spectrometry. The mechanism of ZEA binding was also investigated.

In Vitro and In Vivo Evaluation of Lactobacillus delbrueckii subsp. bulgaricus KLDS1.0207 for the Alleviative Effect on Lead Toxicity

Lead (Pb) is a toxic contaminating heavy metal that can cause a variety of hazardous effects to both humans and animals. In the present study, Lactobacillus delbrueckii subsp. bulgaricus KLDS1.0207 (L. bulgaricus KLDS1.0207), which has a remarkable Pb binding capacity and Pb tolerance, was selected for further study. It was observed that the thermodynamic and kinetic model of L. bulgaricus KLDS1.0207 Pb binding respectively fit with the Langmuir-Freundlich model and the pseudo second-order kinetic model. Scanning electron microscopy and energy dispersive spectroscopy analysis disclosed that the cell surfaces were covered with Pb and that carbon and oxygen elements were chiefly involved in Pb binding. Combined with Fourier transform infrared spectroscopy analysis, it was revealed that the carboxyl, phosphoryl, hydroxyl, amino and amide groups were the main functional groups involved in the Pb adsorption. The protective effects of L. bulgaricus KLDS1.0207 against acute Pb toxicity in mice was evaluated by prevention and therapy groups, the results in vivo showed that L. bulgaricus KLDS1.0207 treatment could reduce mortality rates, effectively increase Pb levels in the feces, alleviate tissue Pb enrichment, improve the antioxidant index in the liver and kidney, and relieve renal pathological damage. Our findings show that L. bulgaricus KLDS1.0207 can be used as a potential probiotic against acute Pb toxicity.