Ultrafiltration Tests Research Articles

Assessment and Development of Bone Preparation for Radiocarbon Dating at HEKAL

ABSTRACTBone is one of the most complex sample materials used for radiocarbon (14C) dating. The installation of the EnvironMICADAS AMS at HEKAL (department of ICER) in 2011 required the adoption of new sample preparation techniques for small bone samples. Since then, hundreds of procedural background and known-age bones have been processed using our modified Longin method (MLM) and dated along with unknown samples. Their results are used in this study to assess the reproducibility of our current bone preparation method and the real uncertainty of the final age result. In addition, using the background samples, which are included in each bone measurement batch, blank correction of the unknown samples could also be performed. The mean F14C value of our bone blanks is generally better than 0.005 (∼42,500 BP) alongside 0.0013 SD. Good reproducibility was confirmed by the results of the laboratory known-age bone as well, where the standard deviation of the mean is better than 0.0025. In addition, the results of the three bone samples used in an ultrafiltration (UF) test study did not show notable differences from the ones obtained by our current protocol in 1σ uncertainty range but more experiments will be performed in the near future.

Binding of model polycyclic aromatic hydrocarbons and carbamate-pesticides to DNA, BSA, micelles and liposomes

The binding to biosubstrates and micellar systems of pollutants as the polycyclic aromatic hydrocarbon (PAH) derivatives 1-aminopyrene (1-PyNH2) and 1-hydroxymethylpyrene (1-PyMeOH) and the carbamate-pesticides 1-naphthyl-N-methylcarbamate (carbaryl, CA) and methyl benzimidazol-2-ylcarbamate (carbendazim, CBZ) was analysed through an integrated strategy combining spectroscopy and quantum chemistry. As biosubstrates, natural DNA and bovine serum albumin (BSA) were taken into account for a thermodynamic analysis of the binding features through spectrophotometric and spectrofluorometric techniques. In all cases, a strong DNA interaction is present and intercalation is supposed as the major binding mode. For the PAH derivatives, DNA binding is found to be favoured under high salt conditions and BSA static quenching and binding with 1:1 stoichiometry occurs. The molecular structure and optical properties of 1-PyNH2, CA and CBZ together with their intercalated adducts in DNA were studied also by means of quantum chemical approach. The (TD)DFT calculations on intercalated dye/DNA adducts quantitatively reproduce the experimentally observed spectroscopic changes, thus confirming the intercalation hypothesis. The theoretical approach also provides information on the adducts' geometries and on the amount of charge transfer with DNA. Moreover, ultrafiltration tests in the presence of anionic (SDS), cationic (DTAC) and neutral (Triton X) micellar aggregates and liposomes provided insights into lipophilicity and cellular membrane affinity. PAH derivatives show high retention coefficient in all cases, whereas in the case of carbamate-pesticides micellar retention might be significantly reduced and is very limited in the case of liposomes.

The performance of bovine serum albumin filtration by using polyethersulfone-Tetronic 304 blend Ultrafiltration Membrane

Background: Membrane technology has been widely applied for protein purification. In applications for protein separation, a membrane with stable filtration performance is necessary. In this work, two types of hollow fiber membranes with different characteristic were used to study the filtration profile of bovine serum albumin. Methods: A single piece of hollow fiber module was used for ultrafiltration testing using UF0 and UFT304 membranes. Flux and rejection of BSA solution were collected based on a pressure-driven inside filtration model. Results: Ultrafiltration experiments showed that the flux of UFT304 membrane was higher than that of UF0 membrane in all applied pressure condition. Solute rejection was achieved up to 90% for ultrafiltration of BSA solution by using UF0 membrane obtained on the operating pressure of 0.5 atm. Conclusion: In general, UFT304 membranes has better ultrafiltration performance for BSA separation than UF0 membranes. The UFT304 membrane has a more stable flux for up to two hours of filtration.

Study on the Mechanism of Humic Acid on Ultrafiltration Membrane

In view of the problem of clogging of ultrafiltration membrane in ultrafiltration process, the contamination mechanism of humic acid solution on ultrafiltration membrane was studied in depth. Through the ultrafiltration test of different concentrations of humic acid solution, it was found that humic acid can cause pollution to the ultrafiltration membrane, and the higher the humic acid concentration, the more serious the membrane contamination. The introduction of calcium carbonate particles can delay the progress of ultrafiltration membrane fouling in the initial stage of ultrafiltration, but as the ultrafiltration time increases, the membrane fouling rate increases rapidly. The kaolin particles can aggravate the contamination of the ultrafiltration membrane by humic acid, and the contamination can be washed away by the aqueous sodium hydroxide solution. The introduction of calcium ions can significantly aggravate membrane fouling and polymerize humic acid molecular chains. Sodium hydroxide and sodium hypochlorite alkali solution can effectively remove the humic acid pollution on the ultrafiltration membrane, wherein the sodium hydroxide solution has better cleaning effect, and the calcium carbonate-containing pollutant can be washed with a citric acid solution.

Preparation of geopolymer inorganic membrane and purification of pulp-papermaking green liquor

This paper describes a low-cost and highly efficient metakaolin-based geopolymer composite membrane (support + dense layer) at normal pressure and <70 °C. The support was fabricated using geopolymer foam materials and shows a large water flux and good mechanical properties. The dense layer was prepared using a dip-coating process with geopolymer paste on the porous geopolymer support surface. This study explored the influence of the foam agent content on the support membrane microstructure, water flux and compressive strength, and determined that the optimal foam agent content is 1.0 mass%. By adjusting the viscosity of the geopolymer paste in accordance with the water flux and removal rate, the thickness of the dense layer was determined as 500 μm. The composite membrane shows a distribution of pore sizes (approximately 0.09 μm of dense layer), amorphous structure, high permeable water flux (245 kg·m−2·h−1), good interface combination and can be reused. The preliminary ultra-filtration test (0.2 MPa operation pressure) demonstrates that the geopolymer-based composite membrane can effectively treat suspended particles in wastewater and is expected to be applied in the field of wastewater treatment. We then used the composite membrane in the pulp-papermaking green liquor at different temperatures, and it was found that the SS (suspended solids) of the filtrate can be decreased to 3.45 mg/L at 80 °C or to 0.79 mg/L at 30 °C, far below the industrial requirements of green liquor recycling (SS < 20 mg·L−1).

Effect of metabolic uncoupler, 2,4‑dinitrophenol (DNP) on sludge properties and fouling potential in ultrafiltration membrane process

Energy uncoupling technology was applied to the membrane process to control the problem of bio-fouling. Different dosages of uncoupler (2,4‑dinitrophenol, DNP) were added to the activated sludge, and a short-term ultrafiltration test was systematically investigated for analyzing membrane fouling potential and underlying mechanisms. Ultrafiltration membrane was used and made of polyether-sulfone with a molecular weight cut off (MWCO) of 150 kDa. Results indicated that low DNP concentration (15–30 mg/g VSS) aggravated membrane fouling because more soluble microbial products were released and then rejected by the membrane, which significantly increased cake layer resistance compared with the control. Conversely, a high dosage of DNP (45 mg/g VSS) retarded membrane fouling owing to the high inhibition of extracellular polymeric substances (proteins and polysaccharides) of the sludge, which effectively prevented the formation of cake layer on the membrane surface. Furthermore, analyses of fouling model revealed that a high dosage of DNP delayed the fouling model from pore blocking transition to cake filtration, whereas this transition process was accelerated in the low dosage scenario.

Sunlight irradiation triggers changes in the fouling potentials of natural dissolved organic matter

Sunlight-initiated photodegradation has a great impact on the composition and properties of natural dissolved organic matter (DOM) in aquatic environments, which potentially changes the behavior and roles of DOM in water treatment facilities. Here, we explored the effect of sunlight irradiation on membrane fouling behavior of two natural DOM (i.e., Aldrich humic acid (AHA) and Suwannee River DOM (SRNOM)), particularly in the presence of calcium ion (Ca(II)). Results showed that a long-term exposure (3 months) to sunlight during the summer led to decreases in the chromophores and molecular size of both DOM. The characterization by UV–vis spectral parameter DSlope350–400 (the slope of the log-transformed absorbance spectra in the range of 350–400 nm) indicated that sunlight-exposed DOM had a weaker Ca(II)-binding ability than unirradiated DOM, which could be attributable to the photochemically induced loss of carboxyl and phenolic groups. Additionally, AHA was found to be more susceptible to sunlight irradiation and Ca(II) addition than SRNOM, likely due to its higher aromaticity. Crucially, dead-end ultrafiltration tests showed that sunlight exposure of both AHA and SRNOM can reduce their fouling potential in the absence of Ca(II) and the presence of low Ca(II) (0.4 mM). In contrast, the addition of higher Ca(II) concentrations (2 and 3.6 mM) led to an increase in their fouling propensities. Overall, sunlight exposure can greatly alter the fouling behavior of natural DOM. This study provides a nexus between the naturally occurring transformation of DOM and its behavior (i.e., membrane fouling) in water treatment facilities.

Modelling approach to an ultrafiltration process for the removal of dissolved and colloidal substances from treated wastewater for reuse in recycled paper manufacturing

In this work, ultrafiltration (UF) is used to remove dissolved and colloidal substances (DCS) from a secondary clarifier effluent from a wastewater treatment plant (WWTP) in a papermaking factory. The approach has been to examine and model the decline in permeate flux resulting from membrane fouling. Effluent from a WWTP at a papermaking factory, previously filtered, was used as feed. UF experiments were carried out in a laboratory-scale plant using a 10kDa polyethersulfone (PES) UF membrane in a flat sheet module with an active area of 154.8cm2. The transmembrane pressure (TMP) (1–3bar) and crossflow rate (1.5–4.5L/min) were varied during the experiments, at constant temperature (22±0.5°C). Experimental results from UF tests were expressed in terms of permeate flux (Jp) as a function of time to check modified Hermia’s models adapted to crossflow filtration. The parameters of these models were theoretically estimated. The predicted results were compared with experimental data with a high goodness of fit. The results showed that the phenomenon controlling fouling, under most of the conditions tested, was intermediate blocking (R2>0.96). Measurements of particle size distribution and zeta potential near the isoelectric point, showed a substantial reduction in colloidal compounds. Additionally, given that COD was removed down to 110mg/L, it could be said that UF is suitable for producing water that can be reused in different papermaking processes.

3D printed feed spacers based on triply periodic minimal surfaces for flux enhancement and biofouling mitigation in RO and UF

In this proof of concept study, 3D printed feed spacers with complex geometries based on triply periodic minimal surfaces (TPMS) were designed and tested in reverse osmosis (RO) and ultrafiltration (UF) processes. The spacers showed flux enhancement of 15.5% and 38% in brackish water RO and UF tests with sodium alginate solution, respectively, in comparison to a commercial feed spacer. Moreover, lower feed channel pressure drop was also observed for the TPMS spacers. Biofouling tests were performed and the membranes were characterized using total organic carbon (TOC) and fluorescence microscopy. The TPMS spacers yielded a reduction in biofouling when compared to commercial feed spacers. Fouling patterns on the membranes were visualized for the different spacers using crystal violet stain, which also revealed a significantly reduced biofilm deposition using the TPMS spacers. The TPMS-based feed spacers have shown great promise in enhancing both RO and UF membrane processes, both in terms of flux enhancement and fouling reduction.

Influence of the polyacrylonitrile proportion on the fabricated UF blend membranes’ performance for humic acid removal

Abstract Asymmetric blend membranes of polyethersulfone (PES)/polyacrylonitrile (PAN) were prepared and developed for ultrafiltration applications. The membranes were prepared by dissolving two polymers in N-methyl-2-pyrrolidone (NMP) as a solvent with diethylene glycol (DEG) and polyvinylpyrrolidone (PVP) as non-solvent and pore former, respectively. The produced membranes were characterized by scanning electron microscopy (SEM) and fourier transform infrared (FTIR) spectroscopy, and the hydrophilicity of membranes was tested by contact angle measurements. The performance of prepared membranes was carried out by an ultrafiltration testing unit, where the efficiency of membranes was determined according to the humic acid separation and treated water permeate flux. The results indicated that using 1 wt.% of PAN in polymer mixture provided a blending membrane with high mechanical properties and high performance; the humic acid rejection reached 92.47% with treated water permeate flux 70 l/m2·h at feed pressure 6 bar.

Magnetoresponsive Poly(ether sulfone)-Based Iron Oxide cum Hydrogel Mixed Matrix Composite Membranes for Switchable Molecular Sieving.

Stimuli-responsive membranes that can adjust mass transfer and interfacial properties "on demand" have drawn large interest over the last few decades. Here, we designed and prepared a novel magnetoresponsive separation membrane with remote switchable molecular sieving effect by simple one-step and scalable nonsolvent induced phase separation (NIPS) process. Specifically, poly(ether sulfone) (PES) as matrix for an anisotropic membrane, prefabricated poly(N-isopropylacrylamide) (PNIPAAm) nanogel (NG) particles as functional gates, and iron oxide magnetic nanoparticles (MNP) as localized heaters were combined in a synergistic way. Before membrane casting, the properties of the building blocks, including swelling property and size distribution for NG, and magnetic property and heating efficiency for MNP, were investigated. Further, to identify optimal film casting conditions for membrane preparation by NIPS, in-depth rheological study of the effects of composition and temperature on blend dope solutions was performed. At last, a composite membrane with 10% MNP and 10% NG blended in a porous PES matrix was obtained, which showed a large, reversible, and stable magneto-responsivity. It had 9 times higher water permeability at the "on" state of alternating magnetic field (AMF) than at the "off"-state. Moreover, the molecular weight cutoff of such membrane could be reversibly shifted from ∼70 to 1750 kDa by switching off or on the external AMF, as demonstrated in dextran ultrafiltration tests. Overall, it has been proved that the molecular sieving performance of the novel mixed matrix composite membrane can be controlled by the swollen/shrunken state of PNIPAAm NG embedded in the nanoporous barrier layer of a PES-based anisotropic porous matrix, via the heat generation of nearby MNP. And the structure of such membrane can be tailored by the NIPS process conditions. Such membrane has potential as enabling material for remote-controlled drug release systems or devices for tunable fractionations of biomacromolecule/-particle mixtures.

Dead end ultra-filtration of sugar beet juice expressed from cold electrically pre-treated slices: Effect of membrane polymer on fouling mechanism and permeate quality

Abstract Purification of raw sugar beet juice expressed at ambient temperature (20 °C) from pretreated sugar beet slices by pulsed electric field (E = 600 V·cm− 1, tPEF = 10 ms, T = 20 °C) was studied on the laboratory scale by dead-end ultrafiltration tests. Polyethersulfone (PES) and Regenerated Cellulose (RC) membranes with the same nominal molecular weight cut-off of 30 kDa were used. Experiments were carried out in unstirred and stirred (at rotation speed of 500 rpm) mode at constant trans-membrane pressure of 2 bar. The effects of the membrane polymer (Polyethersulfone and Regenerate Cellulose) on the filtration flux and the permeate quality were studied. In order to identify the fouling mechanism, the filtration kinetics was modeled using combined fouling models. Results showed that the filtration productivity (filtration flux) and selectivity (rejection ratio of impurities) depended on the membrane polymer. The juice filterability was better with Regenerated Cellulose (RC) membrane while the polyethersulfone (PES) membrane ensured a better retention of impurities (colorants, proteins and colloids), leading to a higher juice purity. Experimental and models data adjustment showed that combined models were preferable to investigate the fouling mechanism for both unstirred and stirred filtration. The desirable sugar purity (95–96%) of filtrate implies the potential application of a novel process (PEF treatment-cold pressing-ultrafiltration) for sugar industrial production. Industrial relevance Pre-treatment by pulsed electric field PEF allowed cold or mild extraction of sucrose from sugar beet roots. The combination of PEF and ultra-filtration allowed high yield sucrose extraction and purification with less energy consumption. Membrane fouling analysis led to better filtration producibility. The obtained data can be useful for optimization of the sucrose production with high yield in industrial extraction processes.

Evolution of organic gel fouling resistance in constant pressure and constant flux dead-end ultrafiltration: Differences and similarities

A common type of ultrafiltration (UF) membrane fouling is due to organic gel, encountered in the treatment of various effluents and feed waters to desalination plants; polysaccharides are a major component of such fouling layers. In standard methods, dead-end UF tests under constant pressure are used to determine membrane-fouling propensity, but the results are applied with questionable success to the case of constant flux filtration, favored in practice. Observed differences between fouling resistances from the two modes of UF filtration have not been adequately explained yet. The temporal evolution of specific resistance α (considered as the most representative fouling parameter) is investigated herein, aiming to elucidate differences and possible similarities in the different filtration modes. During alginate-solution ultrafiltration, typical gel-type membrane fouling layers are formed with time-varying deposited mass density m (g/cm2) depending on permeate flux; thus, the temporal variation of specific resistance α, of pressure difference across the fouling layer/cake ΔPc, and of pressure drop per unit depth of cake (the latter proportional to ΔPc/m) are studied for both constant pressure P and constant flux J operation, within P and J ranges of practical interest. These detailed data suggest that permeation flux is the process variable controlling the development of resistance α. Specifically, for constant-flux filtration, the resistance α data are well correlated with flux J (as also shown recently), whereas in the constant-pressure mode the commonly observed constant resistance α, over a rather broad range of declining flux, is due to the high flux level prevailing in the early stage of filtration. A successful approach is demonstrated to compare and correlate the specific resistance α data obtained from the two different filtration modes. The usefulness of the new results in practice is also discussed.

Bench-scale study of ultrafiltration membranes for evaluating membrane performance in surface water treatment

Currently, there is no standard bench-scale dead-end ultrafiltration (UF) testing system. The aim of the present study was to design and build a bench-scale hollow fiber UF system to assess the impact of operational parameters on membrane performance and fouling. A bench-scale hollow fiber UF system was built to operate at a constant flux (±2% of the set-point flux) and included automated backwash cycles. The development of the bench-scale system showed that it is very difficult to maintain a constant flux during the first minute of the filtration cycles, that digital flow meters are problematic, and that the volume of the backwash waste lines should be minimized. The system was evaluated with Ottawa River water, which has a relatively high hydrophobic natural organic matter content and is typical of Northern Canadian waters. The testing using different permeate fluxes, filtration cycle duration and backwash cycle duration showed that this system mimics the performance of larger systems and may be used to assess the impact of operating conditions on membrane fouling and alternative pretreatment options. Modeling the first, middle, and last filtration cycles of the six runs using single and dual blocking mechanisms yielded inconsistent results regarding the controlling fouling mechanisms.

Production of lactic acid by ultrafiltration of fermented whey obtained in bioreactor equipped with ZOSS membrane

Experimental investigation on cross-flow and pressure ultrafiltration (UF) fermentation broth of lactic acid during the whey fermentation using a bioreactor equipped with zirconium oxide stainless steel (ZOSS) membrane was carried out. Different filtration resistance (Rf and Ri) components were calculated to understand better the interactions between the membrane and fermentation feed. Various raw materials (deproteinated synthetic whey S1, model/synthetic whey S2 and ultrafiltration dairy whey permeate S3) were used as a feed for UF tests under constant conditions. It was found that the highest concentration of lactic acid in permeate (0.69±0.95%wt.) as well as permeate flux (0.5±5.5·10−6m3m−2s−1) was obtained with the transmembrane pressure of 2·106Pa and the cross-flow velocity of 1ms−1. Under these conditions the fouling resistance of 6.87·1011m−1 was minimal. The integration of bioreactor with ZOSS membranes seems to be promising concept in the production and filtration of lactic acid in the dairy industry.

Novel strategies for diagnosing the cause of short-term organic fouling in ultrafiltration

ABSTRACTThe main objective of this study was to demonstrate the usefulness of a multi-strategic approach for identifying the extent and mechanism of fouling in the ultrafiltration (UF) of wastewater effluent organic matter (EfOM). In this study, we combined EfOM fractionation with spectroscopic autopsies for clean and fouled UF membranes. The EfOM fractions were sequentially removed from the wastewater effluent using relatively gentle techniques (neutral pH and no extractions). The residual EfOM samples were then used in UF tests. This work showed that resistance to filtration was partially reduced with the removal of particles (>20 nm), but almost all of the short-term fouling was eliminated with the removal of organic acids, which constitute 22% of the total organic carbon. The membrane autopsies were conducted using attenuated reflectance infrared spectroscopy for the top and bottom fouled membranes, and comparison was made with the infrared spectra of a clean membrane. Hydrophilic base/neutrals were the dominant EfOM constituents at the top of the fouled membranes. Hydrophobic acids were adsorbed onto the pore walls deep inside the membranes, which coincided with the permeability recovery of fouled membranes. The fouling mechanisms were examined by measuring the resistance to filtration as a function of permeate flux using various operational conditions and by investigating the effectiveness of hydraulic and chemical cleaning on the restoration of membrane permeability.

Construction of microgels embedded robust ultrafiltration membranes for highly effective bioadhesion resistance

Effective and robust anti-bioadhesion ultrafiltration membranes were fabricated in this paper via physically blending of anti-bioadhesion microgels. The microgels were synthesized by one-step cross-linking of antifouling segment, poly(ethylene glycol) methacrylate (PEGMA), and electrostatic repulsion segment, methylacrylic acid (MAA). Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) results indicated that large amounts of PEGMA and MAA polymers had been enriched on the membranes surface. Scanning electron microscope (SEM) indicated that the spherical PEGMA-MAA (PM) microgels might form interpenetrating structure with the membrane matrixes, and substantially increased the pore size of the membranes. Water contact angle (WCA), pore size distributions and ultrafiltration tests suggested that the hydrophilicity, porosity, water flux, and antifouling property for the modified membranes were significantly enhanced. More importantly, systematic anti-adhesion investigations of plasma proteins, platelets, bacteria and vein endothelial cells confirmed that the modified membranes owned strong resistance capability to the bioadhesion of various organisms. The results revealed that highly robust and effective anti-bioadhesion ultrafiltration membranes could be prepared via the proposed blending of PM microgels with membrane matrix, thus this approach should be potential in various biomedical or industrial filtration fields where anti-bioadhesion properties were highly demanded.

Study of the influence of operational conditions and hollow-fiber diameter on the ultrafiltration performance of a secondary treatment effluent

Secondary treatment effluents from municipal wastewater treatment plants (MWWTP) must achieve high water quality standards for their reuse in agriculture. To achieve these standards, ultrafiltration (UF) process, which is economically feasible, is carried out. However, UF has a drawback, membrane fouling, which causes operating difficulties and an increment of the operating cost. In order to minimize this phenomenon, it is important to determine the best operational conditions. Wastewater samples provided by MWWTP have a lot of variability in their composition due to factors such as temperature, efficiency of the secondary treatment, etc. Besides, the soluble microbial products of the secondary effluent are dependent on the type of the biological treatment implemented and its operating conditions. A model wastewater feed solution was prepared consisting of 15 mg/L of bovine serum albumin and 5.5 mg/L of dextran. In this research, UF tests were performed with the optimal simulated wastewater using two membranes UFCM5 Norit X-flow® hollow-fiber: one of them with a fiber diameter of 1.5mm and the other one with a fiber diameter of 0.8 mm. The operational conditions, which influence membrane fouling, were varied in the range of 62–100 kPa for transmembrane pressure (TMP) and in the range of 0.8–1.2 m/s for cross-flow velocity (CFV). The best operational conditions were selected in terms of higher permeate flux. The highest permeate flux was obtained for the membrane of 0.8mm and the lower energy consumption was achieved at a CFV of 1.2 m/s and a TMP of 62 kPa.

Laboratory-scale membrane up-concentration and co-anaerobic digestion for energy recovery from sewage and kitchen waste.

This study assessed an alternative concept for co-treatment of sewage and organic kitchen waste in Vietnam. The goal was to apply direct membrane filtration for sewage treatment to generate a permeate that is suitable for discharge. The obtained chemical oxygen demand (COD) concentrations in the permeate of ultrafiltration tests were indeed under the limit value (50 mg/L) of the local municipal discharge standards. The COD of the concentrate was 5.4 times higher than that of the initial feed. These concentrated organics were then co-digested with organic kitchen wastes at an organic loading rate of 2.0 kg VS/m(3).d. The volumetric biogas production of the digester was 1.94 ± 0.34 m(3)/m(3).d. The recovered carbon, in terms of methane gas, accounted for 50% of the total carbon input of the integrated system. Consequently, an electrical production of 64 Wh/capita/d can be obtained when applying the proposed technology with the current wastes generated in Ho Chi Minh City. Thus, it is an approach with great potential in terms of energy recovery and waste treatment.

Screening of plantaricin EF and JK in an Algerian Lactobacillus plantarum isolate

ObjectiveTo isolate an antagonistic Lactobacillus strain from healthy infant feces and estimate its potential against a range of Gram-positive and Gram-negative bacteria. MethodsIsolation was based on biochemical tests and on 16S rDNA sequences. A PCR based screening of plantaricin bacteriocin encoding genes was conducted using specific primers. Antimicrobial activity was realized using spot on agar and agar well-diffusion tests. Spent culture supernatant was subjected to ultrafiltration. Effect of mitomycin C and UV light, heat treatment, storage, pH and enzymes were tested. ResultsBiochemical tests and 16S rDNA sequences showed that LbM2a belonged to Lactobacillus plantarum. Screening of plantaricin genes showed the presence of plantaricin EF and K. Ultrafiltration tests lead to estimate the molecular weight between 3 and 10 kDa. LbM2a showed a broad inhibitory activity, which was stable at pH range of 2.0 to 6.0 and was proteinaceous (inactivation by proteolytic enzymes). Mitomycin C and UV light did not affect the activity. ConclusionsThe paper illustrates that the ability of isolate and its bacteriocins in inhibiting a wide-range of bacteria are great interest for food safety and might have future applications as food preservative.