Μm Membrane Research Articles

Determination of aminoglycoside antibiotics in animal feed by high performance liquid chromatography using evaporative light scattering detector

This study was carried out to develop a method for the simultaneous analysis of 5-aminoglycosides such as streptomycin (STR), neomycin (NEO), kanamycin (KAN), spectinomycin (SPE), and amikacin (AMI) in animal feedstuffs using the (HPLC-ELSD) high performance liquid chromatography with Evaporative Light Scattering Detector detection. The 5-aminoglycoside antibiotics in animal feed samples were extracted with a solvent containing 20% ACN, 1% HCl (v/v). The extract was purified by solid-phase extraction (SPE) with the stationary phase of PCX, at pH 5 which was adjusted by NH3 solution. The 5-aminoglycosides were eluted from the SPR column with 10% NH3 solution. The eluted sample was evaporated to dryness and the residue was dissolved in 20 mM hepta fluorobutyric acid (HFBA) solution followed by filtering through a 0.22 µm membrane prior to analyze by HPLC – ELSD. The 5-aminoglycosides were separated on an Eclipse Plus C18, 1.8 µm, 4.6×100 mm column, an aqueous/acetonitrile containing 15 mM HFBA in gradient mode with ratio of H2O/ACN: 0-1 min fix at 76:25, 1-6 min reduce 55:45, 6-7 min fix at 55-45, 7-8 min increase to 75:25. A carrier gas velocity of the ELSD detector was 1 L/min and the misting temperature was 40oC. This method achieved a detection limit (MDL) of 4 mg/kg and a recovery yield of 87-92% for 5-aminoglycosides in feed sample with the HPLC – ELSD system.

Microbial Analysis of Drinking Water from Randomly Selected Boreholes and Shallow Wells around Hargeisa, Somaliland

Background: Shallow wells and boreholes are vital sources of potable water in Hargeisa. This water can be polluted by runoff, in particular during the rainy season, causing outbreaks of waterborne infections. Objectives: This research aimed at evaluating the microbial quality of shallow wells and boreholes water around Hargeisa, Somaliland. Methods: The total coliform and Escherichia coli count were done by using the membrane filtration method. Overall, 100 ml of each water sample was filtered via a 0.45 μm membrane filter, and then the filters were put on m-Endo agar plates that were incubated at 37°C for 24 to 48 hours. Results: The mean value of total coliform counts for the boreholes and shallow wells ranged from 1.288 × 103 to 8.8 × 103 CFU/100ml, while the mean value of total E. coli counts also ranged from 3.5 × 102 to 4.429 × 103 CFU/100ml. Results from this study have demonstrated that all water sources (Arabsiyo, Dararweyne, Darasalaam, Dabaraqas, and Jaleelo) don’t comply with the WHO guideline for drinking water. Results from the analysis of water samples of 28 wells demonstrated a significant correlation between total coliform and E. coli counts (P = 0.01). Therefore, this water is not fit for human consumption unless it is treated. Conclusion: This study has demonstrated that all results of both mean values of total coliform and E. coli counts from groundwater of selected shallow wells and boreholes were beyond WHO standards, so water from Arabsiyo, Jaleelo, Dabaraqas, Dararweyne, and Darasalaam requires treatment before human consumption.

Influence of Transglutaminase Crosslinking on Casein Protein Fractionation during Low Temperature Microfiltration.

Low temperature microfiltration (MF) is applied in dairy processing to achieve higher protein and microbiological quality ingredients and to support ingredient innovation; however, low temperature reduces hydrophobic interactions between casein proteins and increases the solubility of colloidal calcium phosphate, promoting reversible dissociation of micellar β-casein into the serum phase, and thus into permeate, during MF. Crosslinking of casein proteins using transglutaminase was studied as an approach to reduce the permeation of casein monomers, which typically results in reduced yield of protein in the retentate fraction. Two treatments (a) 5 °C/24 h (TA) and (b) 40 °C/90 min (TB), were applied to the feed before filtration at 5 °C, with a 0.1 µm membrane. Flux was high for TA treatment possibly due to the stabilising effect of transglutaminase on casein micelles. It is likely that formation of isopeptide bonds within and on the surface of micelles results in the micelles being less readily available for protein-protein and protein–membrane interactions, resulting in less resistance to membrane pores and flow passage, thereby conferring higher permeate flux. The results also showed that permeation of casein monomers into the permeate was significantly reduced after both enzymatic treatments as compared to control feed due to the reduced molecular mobility of soluble casein, mainly β-casein, caused by transglutaminase crosslinking.

In vivo Imaging of Retina and Choroid in Guinea Pigs.

Purpose: To evaluate the feasibility of in-vivo imaging of the retina and choroid using spectral domain optical coherence tomography (OCT) in guinea pigs.Methods: The study included 19 pigmented guinea pigs (age: 3–4 weeks) which underwent sonographic axial length measurements and OCT imaging. At study end, the animals were sacrificed and histomorphometric examinations of the retina and choroid were performed. We assessed the reproducibility of the OCT measurements and compared in-vivo measurements to histomorphometric data.Results: The mean thickness of the retina and choroid near the optic nerve head was 175.6 ± 25.8 and 63.4 ± 16.5 μm, respectively, and mean Bruch's membrane opening (BMO) diameter was 831 ± 121 μm. The intra-observer comparison of measurements of retinal thickness (intraclass correlation coefficient (ICC) = 0.92, 95% CI: 0.86–0.96; P < 0.001), choroidal thickness (ICC = 0.92, 95% CI: 0.86–0.96; P < 0.001), and BMO diameter (ICC = 0.92, 95% CI: 0.86–0.96; P < 0.001) showed a high correlation. A high agreement was present also for the inter-observer reproducibility of the measurements of retinal thickness (Pearson correlation coefficient (R) = 0.98; P < 0.001), choroidal thickness (R = 0.96; P < 0.001), and BMO diameter (R = 0.98; P < 0.001). The Bland-Altman plots showed that 2.6% (1/38), 5.3% (2/38), and 7.9% (3/38) of the measurement points of retinal thickness, choroidal thickness and BMO diameter, respectively, were located outside of the 95% limits of agreement. The OCT-based thickness measurements of retina and choroid were significantly higher than those measured by histomorphometry (both P-values <0.01).Conclusion: OCT-based in-vivo morphometric imaging of the retina and choroid in guinea pigs is feasible with an acceptable intra-observer repeatability and inter-observer reproducibility.

Microfiltration membranes developed from nanofibers via an electrospinning process

Membranes act as a barrier in the separation of two distinct phases, usually under a driving force, such as a pressure or concentration gradient. Compared to other types of conventional separation processes, membranes have such advantages as centrifugation, sedimentation, low energy and operating costs and high process efficiency. Therefore, nanofiber membranes developed via an electrospinning process were explored as microfiltration media in the separation of microparticles. Polyacrylonitrile nanofibers, with an average diameter of 580 ± 57 nm, were developed via the electrospinning process. The nanofiber membranes resulted in a hydrophilic nanostructured material with a porosity of approximately 79.5% and a pure water flow of ∼19,500 L h−1 m−2. Efficient filtration was achieved with total retention of particles of diameter ∼1.75 μm using a 146 μm membrane. The electrospinning process enables the production of nanofiber membranes with potential applicability for efficient separation of microparticles in suspension.

Aquaculture waste nutrients removal using microalgae with floating permeable nutrient uptake system (FPNUS)

Large area requirements and huge energy consumption restrict the applications of microalgae in wastewater treatment. In this study, in-situ nutrient removal was tested using a floating permeable nutrients uptake system with pore sizes of 1, 5, 10, and 40 µm, and Chlorella sorokiniana and Scenedesmus acuminatus. Results showed that N transfer rate across FPNUS varied with membrane pore size and N-type. Average transfer rate of NH4+-N, NO3–-N, and NO2–-N across 1 µm membrane was 2.6, 14.6, and 2.3 mg m-2h−1, respectively, sufficient to support microalgal growth. The NH4+-N and NO3–-N removal rate in shrimp wastewater reached 1.32 and 1.88 mg L-1d-1, comparable to some BNR processes used in RAS. According to the developed area ratio prediction model, FPNUS to pond area ratio of 21% is sufficient to balance N loading of 0.05 mg L-1d-1. These results indicate extraordinary potential of in-situ nutrient removal from wastewaters using FPNUS.

In vitro antifungal activity of Candida culture extracts against Trichophyton rubrum and Trichophyton mentagrophytes.

Onychomycoses are nail infections caused primarily by dermatophytes fungi, yeasts, and other filamentous fungi, characterized by persistent infections, prolonged therapy, and high recurrence rates. In clinical practice, some of these occurrences present two or more microorganisms, and the interactions among them can change the chemical environment mediated by small diffusible molecules, producing a competitive niche. The aim of this study was to evaluate the antifungal activity of individual extracts of pure cultures of Candida albicans and C. parapsilosis against dermatophytes. To obtain the fungal extracts, cultures were filtered through a 0.2 μm membrane and submitted to liquid-liquid extraction using ethyl acetate. The Minimal Inhibitory Concentration (MIC) of each extract was evaluated by broth microdilution method and checkerboard assay with fluconazole against clinical isolates of Trichophyton rubrum and T. mentagrophytes. The invertebrate model of Galleria mellonella was used to evaluate the toxicity of the extracts. As results, the extracts of C. albicans and C. parapsilosis showed antifungal activity with MICs between 31,2 – 2000 μg/mL. In association with fluconazole, synergistic effect was detected for all combinations. The extracts presented low toxicity in G. mellonella. In the future, isolation and identification of the extract compounds may allow new therapeutic approaches in the control of fungal infections.

Sample preparation for the analysis of nanoparticles in natural waters by single particle ICP-MS

With the significant increase in the production and use of nanoparticles (NP), concern is increasing over their release into their environment. Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) is emerging as one of the best techniques for detecting the very small NP at very low concentrations in natural waters. However, there is no unified protocol for the preparation of natural water samples for SP-ICP-MS analysis. In order to minimize nebulizer blockage, filtration is often used with the expectation that 0.45 μm membranes will not remove significant quantities of 1–100 nm NP. Nonetheless, there are limited data on its effect on the concentrations or size distributions of the NP. To that end, we examined the interactions between six different membrane filters and silver (Ag) and cerium oxide (CeO2) NP in aqueous samples. For Ag NP, the highest recoveries were observed for polypropylene membranes, where 55% of the pre-filtration NP were found in rainwater and 75% were found in river waters. For CeO2 NP, recoveries for the polypropylene membrane attained 60% in rainwater and 75% in river water. Recoveries could be increased to over 80% by pre-conditioning the filtration membranes with a multi-element solution. Similar recoveries were obtained when samples were centrifuged at low centrifugal forces (≤1000×g).

Determination of donkey skin ingredients in Asini Corii Colla by ultra-high performance liquid chromatography-tandem mass spectrometry

近年来由于驴皮资源短缺,阿胶价格大幅度上涨,市场上出现了大量以马、骡、猪、牛皮等熬制而成的假胶,导致阿胶质量的参差不齐,严重扰乱了市场,急需高效准确的检测方法提升阿胶品质。该研究采用超高效液相色谱-串联质谱技术,建立了阿胶中驴皮源成分的检测方法。样品加水溶解后,于37 ℃下经胰蛋白酶酶解,产生驴源性特征肽段,以0.1%甲酸乙腈溶液和0.1%甲酸水溶液作为流动相进行梯度洗脱,单次分析时间10 min,在电喷雾正离子(ESI+)模式下进行多反应监测(MRM),同位素内标法定量。驴源多肽A1、A2在50~1250 μg/L范围内线性关系良好,相关系数(r)均大于0.996,方法定量限(S/N=10)为20 mg/kg,在300、600、900 mg/kg 3个添加水平上驴源多肽A1、A2的回收率范围为103.2%~108.3%,各加标水平平行测定结果的相对标准偏差(RSD)为1.0%~3.0%,完全能够满足实际样品检测需求。对29批不同生产企业的阿胶进行测定,结果表明,不同企业生产的阿胶中驴源多肽A1、A2的含量之和存在差异,含量为0.096%~0.180%,平均值为0.151%,提示驴源多肽A1、A2含量较低的阿胶生产厂家应注重皮源质量,改进生产工艺,以提升产品质量。该方法操作简便,结果可靠,重现性好,可用于阿胶中驴皮源成分的测定。

Determination of plant growth regulators in animal-derived foods using QuEChERS-isotope-labeled internal standards with high performance liquid chromatography-tandem mass spectrometry

建立了高效液相色谱-串联质谱法测定动物源性食品中植物生长调节剂类农药残留量的方法。选取猪肉、牛肉、鸡肉、猪肝、鸡蛋和牛奶作为样品,样品经乙腈提取,4 g无水硫酸镁(MgSO4)和1 g氯化钠(NaCl)盐析脱水后,取上清液经50 mg N-丙基乙二胺(PSA)+50 mg十八烷基硅烷(C18)粉末净化(含150 mg MgSO4)。采用Agilent ZORBAX Eclipse Plus C18柱分离待测物,电喷雾电离,正负离子切换多反应检测模式检测,以乙腈和5 mmol/L乙酸铵水溶液作为流动相进行梯度洗脱,基质匹配内标法定量。在猪肝、鸡蛋基质中,矮壮素、噻苯隆和多效唑在0.1~100 μg/L范围内线性关系良好;在猪肉、牛肉和鸡肉中3种植物生长调节剂在0.1~50 μg/L范围内线性关系良好;在牛奶基质中,噻苯隆和多效唑的线性范围为0.05~10 μg/L,矮壮素的线性范围为0.05~5 μg/L,相关系数(r2)均大于0.990。以信噪比(S/N)≥3对应的添加水平作为检出限(LOD), S/N≥10对应的添加水平作为定量限(LOQ),矮壮素、噻苯隆和多效唑在不同基质下的LOD为0.01~0.1 μg/kg, LOQ为0.5~5 μg/kg。分别添加LOQ、2倍LOQ和10倍LOQ 3个水平的目标化合物,平均回收率为70.0%~117.4%, RSD为0.8%~16.1%。该方法操作简单、灵敏度高,采用基质匹配内标法定量,能最大限度地消除基质干扰,使检测结果更加精确,可满足动物源性食品中矮壮素、噻苯隆和多效唑残留的定量检测工作。

Enhancing long-term accuracy and durability of wastewater monitoring using electrosprayed ultra-thin solid-state ion selective membrane sensors

Current membrane deposition approaches (e.g., drop-casting, spin-coating) for solid-state ion selective membrane (S-ISM) sensors suffer from problems including sensor material waste, uncontrollable membrane thickness (100–200 μm), loose contact between sensing membrane and electrode surface, long response time (e.g., >20 s) and poor reading stability (e.g., >3 mV/h). This study addressed these challenges by depositing ISM through electrospray printing technology and enabling accurate and continuous monitoring in water and wastewater. Specifically, the final droplet size and the splash diameter of the electrosprayed droplets deposited a particularly tunable, high resolution and ultra-thin (thickness: ∼1 μm) membrane on the electrode surface, which immensely shortened the sensor response time (9.2 s), strengthened the adhesion between the ISM and the electrode surface, mitigated the formation of water layer in the S-ISM sensor entity, and ultimately enhanced the sensor reading stability (reading drifting <0.66 mV/h). Additionally, the ion diffusion model developed in this study confirmed that fast ion diffusion in the electrosprayed S-ISM polymer matrix effectively shortened the response time of sensors. Electrosprayed S-ISM sensors without anti-fouling protection exhibited high stability and accuracy with an error of less than 2.9 mg/L after continuously monitoring wastewater for 10 days, revealing a great potential for further enhancement.

A preliminary electrochemical study of crosslinked albumin and collagen membranes as diffusion barriers for potentially degradable chronic wound biosensors

AbstractThe biochemical monitoring of chronic wounds may help to tailor therapy with better clinical outcomes. Wound surface sensors would be appropriate for this, but their adhesion to the wound is likely to lead to tissue damage on retrieval. Degradable sensors offer a practical solution to this, but this would necessitate external degradable diffusion control membranes. In this study, we evaluated glutaraldehyde crosslinked albumen and collagen as potentially biodegradable barrier membranes. The diffusional transport of H2O2, ascorbate, and glucose was studied electrochemically. Albumin proved more selective for H2O2 against ascorbate, possibly due to its net negative charge. The thick (500–700 μm) membranes produced led to long response times (half‐life [t0.5], 500–700 s) but had the advantage of stabilizing the response in unstirred solution. This was possibly because the thicker membrane on the electrode surface moved the developing diffusion layer in solution further away from the electrode surface. A dense albumin layer was produced using sebacoyl chloride as a crosslinker which was impermeable to solute and could be used in future as a degradable sensor base. Also, non‐toxic poly(2,3‐dihydrothieno‐1,4‐dioxin)‐poly(styrenesulfonate) dispersed in crosslinked albumin furnished a conducting membrane able to function as a working electrode. Thus, crosslinked proteins offer scope for diverse membrane properties that might be useful for future, degradable wound monitoring sensors.

Seasonal ice nucleation activity of water samples from alpine rivers and lakes in Obergurgl, Austria

Heterogeneous ice nucleation plays an important role in many environmental processes such as ice cloud formation, freezing of water bodies or biological freeze protection in the cryosphere. New information is needed about the seasonal availability, nature, and activity of ice nucleating particles (INPs) in alpine environments. These INPs trigger the phase transition from liquid water to solid ice at elevated subzero temperatures. We collected water samples from a series of alpine rivers and lakes (two valleys and their rivers, an artificial pond, and a natural lake system) in Obergurgl, Austria in June 2016, July 2016, November 2016, and May 2017. Each alpine river and lake was sampled multiple times across different seasons, depending on site access during different times of the year. Water samples were filtered through a 0.22 μm membrane filter to separate microbial INPs from the water, and both fractions were analyzed for ice nucleation activity (INA) by an emulsion freezing method. Microorganisms were cultured from the filters, and the cultures then analyzed for INA. Portions of the filtered samples were concentrated by lyophilization to observe potential enhancement of INA. Two sediment samples were taken as reference points for inorganic INPs. Sub-micron INPs were observed in all of the alpine water sources studied, and a seasonal shift to a higher fraction of microbial ice nucleators cultured on selective media was observed during the winter collections. Particles larger than 0.22 μm showed INA, and microbes were cultured from this fraction. Results from 60 samples gave evidence of a seasonal change in INA, presence of submicrometer INPs, and show the abundance of culturable microorganisms, with late spring and early summer showing the most active biological INPs. With additional future research on this topic ski resorts could make use of such knowledge of geographical and seasonal trends of microbial INPs in freshwater habitats in order to improve the production of artificial snow.

Development and Validation of RP-HPLC Method for the Estimation of Clomiphene Citrate in Pharmaceutical Dosage Form

A simple, specific, precise, and accurate RP-HPLC method has been developed and validated for the estimation of Clomiphene citrate in bulk and pharmaceutical dosage form using C18 column Shimadzu (250mm × 4.5mm × 5μm) with a mobile phase consisting of 900mL of HPLC grade methanol and 100mL of HPLC grade acetonitrile. The mobile phase was sonicated for 10 min and filtered through a 0.45μm membrane filter at a flow rate of 1.0mL/min. The detection was carried out at 295nm and retention time of Clomiphene citrate was found to be 3.44 min. Linearity was observed in the concentration range of 10–50μg/mL (coefficient of determination R2=0.999) with regression equation y =20321x + 60021. The method was validated as per ICH guidlines.

Combined macroscopic and pore scale modeling of direct contact membrane distillation with micro-porous hydrophobic membranes

The transport processes of a direct contact membrane distillation (DCMD) module are investigated with a multiscale approach in this study. A stochastic, numerical reconstruction algorithm is first developed to generate 3D virtual membranes based on the membrane's pore size and fiber orientation distributions. Pore-scale simulations are then performed on the reconstructed membrane model. The membrane's effective thermal conductivity and mass diffusivity are computed using AVIZO software and OpenFOAM solver, respectively. A 2D macroscopic, multiphysics model considering the conservation of mass, species, momentum, and energy is developed, where the effective transport properties obtained from pore-scale simulations are utilized, to study the heat and mass transfer through the membrane. Two commercially available polytetrafluoroethylene (PTFE) membranes (GE-Osmonics/0.22 μm and MS-3010/0.45 μm) are chosen as examples for the present multiscale approach. The computed transport properties of the membranes are found to yield good distillate flux predictions with data reported in the literature. The MS-3010/0.45 μm membrane is found to produce 24% higher freshwater on average than GE-Osmonics/0.22 μm membrane. Finally, the performance of DCMD of three hypothetical membranes with different specifications is compared to the reconstructed MS-3010/0.45 μm membrane to study the factors that need to be taken into account for optimal design of the membrane for DCMD applications.

Re-use of waste cotton textile as an ultrafiltration membrane

Textile industry produces millions of tons of waste annually, which is predominantly incinerated or landfilled. Cotton textile comprises a quarter of total textile production, and although being renewable, its production is highly chemical- and water-intensive, rising the need for effective waste cotton textile recycling. This study presents an investigation whether it is possible to utilize waste cotton textile as a cellulose source for the fabrication of cellulose membranes. The effect of casting thickness and cellulose concentration on the prepared membranes’ performance was studied. Membranes cast from 2 wt% casting solutions exhibited the highest permeabilities of 1.11 and 3.09 m3/(m2·s·Pa) for 300 and 150 μm casting thickness, respectively, but poor adhesion stability and low retention. Membranes cast from solutions of higher concentrations (5, 6, and 7 wt%) resulted in membranes with more stable performance. The permeability values for 300 μm membranes were in the range of 0.27 – 0.39 m3/(m2·s·Pa) and for 150 μm 0.51 – 0.67 m3/(m2·s·Pa). The retention values of these six membranes were relatively close to each other, showing 80 – 92% retention of polyethylene glycol (PEG) 35 kDa. Three most promising membranes (5, 6, and 7 wt% cast at 150μm) were additionally characterized, showing negative zeta potential within −23 – −35 mV range at pH 7 and contact angles of very hydrophilic material (14 – 16°). Overall, the results showed that very hydrophilic ultrafiltration membranes having attractive permeability and retention properties can be made from textile waste. 1 m2 of cotton bed linen is enough to produce approximately 20 m2 of cellulose membrane.

Ultrathin Self-Cross-Linked Alkaline Polymer Electrolyte Membrane for APEFC Applications

Ultrathin alkaline polymer electrolyte (APE) membranes have become a hot research topic for high-performance alkaline polymer electrolyte fuel cells (APEFCs). To our knowledge, freestanding ultrathin membranes with thicknesses of or below 10 μm have never been reported for successful applications in APEFCs. The obstacle comes from the poor mechanical strength of the ultrathin membrane during the fuel cell assembly. Herein we report an ultrathin 10 μm membrane made of cross-linked quaternary ammonia poly(N-methylpiperidine-co-p-terphenyl), denoted cQAPPT. This ultrathin cQAPPT membrane is robust enough for fuel cell assembly and demonstrates a high H2/O2 peak power density of 1.85 W/cm2 at 80 °C.

Innovative hydrophobic/hydrophilic perfluoropolyether (PFPE)/polyvinylidene fluoride (PVDF) composite membrane for vacuum membrane distillation

Though membrane distillation (MD) has gained more and more attention in the field of desalination, the wetting phenomenon was still a non-negligible problem. In this work, a method combined dip-coating and UV in situ polymerization for preparing hydrophobic/hydrophilic perfluoropolyether (PFPE)/polyvinylidene fluoride composite membranes. This composite membrane consisted of a top thin hydrophobic coating layer and hydrophilic substrate membrane. In terms of anti-wetting properties, contact angle and liquid entry pressure of all composite membranes (except for those based on 0.45 μm) exceeded 160° and 0.3 MPa, respectively. In particular, the desalination performance was tested in vacuum membrane distillation tests by feeding 3.5% (mass) saline solution (NaCl) at 60 °C. The composite membranes with larger support pore size and lower PFPE content had higher membrane distillation flux. And for stability tests (testing the 0.22 μm membrane coated by 5% (mass) PFPE), the highest MD flux 29.08 kg·m−2·h−1 and stable salt rejection (over 99.99%) during the period. Except that, the effects of coating material concentration and pore sizes of substrate membrane were also investigated for surface morphology and topography, porosity, mechanical strength and pore size characteristics. This work provided a simple and effective alternative to prepare excellent hydrophobic composite membranes for MD applications.

Thickness Effect on Permeance of CO2/CH4 Gases in CA Coated PVDF Composite Membranes

The aim of this work is to study the effect of membrane thickness with respect to gas permeance and tensile strength. The influence of membrane thickness on gas permeation has received little attention to date. Single layer flat sheet membrane with average thickness of 25 μm and dual layer composite membranes with variable thickness of skin layer were fabricated by coating CA/ PEG selective layer on the polyvinylidene fluoride porous support. Permeation experiments were performed with CO2 and CH4 which revealed that permeance of CO2 was pronounced compared to CH4. Highest permeance of 0.87 gas permeation unit (GPU) was obtained at 4 bar with 19.4 μm skin layer. Fourier transform infra-red spectroscopy was used to study the existence of different functional groups in the membranes. Strength of the membranes was analyzed using tensile testing machine. Scanning electron microscopy was used to study the surface structure and morphology. It was found that by reducing the membrane thickness, the permeance of CO2 and CH4 increased without compromising on membrane strength.

Antibacterial Activity of Ethanolic Extract of Matricaria chamomilla, Malva cylvestris, and Capsella bursa-pastoris against Multidrug-Resistant Pseudomonas aeruginosa Strains

Background: This study aimed to determine antibacterial activity of ethanolic extract of Matricaria chamomilla (chamomile), Malva sylvestris, and Capsella bursa-pastoris against multidrug-resistant (MDR) clinical isolates of Pseudomonas aeruginosa. Methods: The plants were collected from Ziarat village of Gorgan, Iran in April 2019. The required parts of the plants were separated and completely dried in the shade. After grinding, extraction was performed by maceration method. The extract was dried at 37°C for 24 hours. To obtain a concentration of 50 mg/mL of each extract, 500 mg of the dried plant extract was dissolved in 10 mL 5% dimethyl sulfoxide and sterilized by filtration through a 0.45 µm membrane filter. For the antibacterial assay, agar well diffusion and broth microdilution methods were used. Results: Based on the results, ethanolic extracts of M. sylvestris and Capsella bursa-pastoris did not show any antibacterial activity against MDR P. aeruginosa isolates in both antibacterial assays. No inhibitory effect was observed for ethanolic extract of chamomile against P. aeruginosa isolates in agar well diffusion method as well. In broth microdilution method, the extract of chamomile leaves showed inhibitory effect and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined as 12.5 and 25 mg/mL, respectively. Conclusions: In this study, the extract of ethanolic chamomile leaves showed antibacterial activity against the MDR P. aeruginosa isolates. Thus, it can be used in the production of antibacterial agents, and it is a good option for protection against pathogenic microorganisms, as well as P. aeruginosa.