Shake Flask Test Research Articles

DETERMINATION ON NITROGEN CONTENT OF ANTIBACTERIAL COTTON FABRIC TREATED WITH CHITOSAN

The study aims to evaluate the nitrogen content on antibacterial cotton fabrics treated with chitosan using four different quantitative determination methods: field-emission scanning electron microscopy with energy dispersive X-ray spectroscopy (FESEM-EDX), dyeability of antibacterial treated samples based on color strength (K/S), elemental analyses via combustion tests, and antibacterial ability under dynamic contact conditions or the dynamic shake flask test. The nitrogen content was analyzed under the effects of molecular weight (MW) of chitosan (2.6 kDa and 187 kDa), crosslinkers including citric acid (CA) and dimethylol dihydroxyethyleneurea (DMDHE), and washing cycles. The findings from these measurements not only determined the nitrogen content of antibacterial cotton fabric but also elucidated the bonding mechanism between cellulose and chitosan in the presence of crosslinking compounds. Consequently, the antibacterial activity of cotton fabrics treated with chitosan could be indirectly assessed through the nitrogen content obtained from the amine groups of finishing compounds.

Biodegradation potentials of edaphic bacterial isolates cultured on Haloxyfop R Methyl ester herbicide-mineral salt medium

The heterotrophic and haloxyfop-R methyl ester utilizing bacterial counts associated with top soil samples was evaluated. Three (3) bacterial isolates; Bacillus sp., Micrococcus sp. and Staphylococcus sp. were cultured and screened for their ability to utilize haloxyfop-R methyl ester as sole source of carbon and energy using the turbidimeteric procedure. The growth profiles of two axenic cultures; Bacillus sp. and Micrococcus sp. were determined using the shake flask test. Parameters which included pH, mean viable bacterial counts, optical density and dissolved CO2 were determined during growth profiling using relevant procedures and equipment. The pH of the soil samples was 5.08 ± 0.02 for sample A and 4.62 ± 0.02 for sample B. The total heterotrophic bacterial count was 2.8 × 104 cfu/g ± 849 for A and 4.62 × 104 cfu/g ± 989 for B. The mean dissolved CO2 data for Micrococcus sp. during the growth profile study ranged from 1.1 mg/l ± 0.1 to 6.8 mg/l ± 0.2. Axenic Micrococcus sp. was the most effective amongst the growth profile cultures in mineralizing the herbicide content of the culture medium.

Facile Modification of Medical-Grade Silicone for Antimicrobial Effectiveness and Biocompatibility: A Potential Therapeutic Strategy against Bacterial Biofilms.

A one-step modification of biomedical silicone tubing with N,N-dimethyltetradecylamine, C14, results in a composition designated WinGard-1 (WG-1, 1.1 wt % C14). A surface-active silicon-amine phase (SAP) is proposed to account for increased wettability and increased surface charge. To understand the mechanism of antimicrobial effectiveness, several procedures were employed to detect whether C14 leaching occurred. An immersion-growth (IG) test was developed that required knowing the bacterial Minimum Inhibitory Concentrations (MICs) and Minimum Biocidal Concentrations (MBCs). The C14 MIC and MBC for Gm- uropathogenic E. coli (UPEC), commonly associated with catheter-associated urinary tract infections (CAUTI), were 10 and 20 μg/mL, respectively. After prior immersion of WG-1 silicone segments in a growth medium from 1 to 28 d, the IG test for the medium showed normal growth for UPEC over 24 h, indicating that the concentration of C14 must be less than the MIC, 10 μg/mL. GC-MS and studies of the medium inside and outside a dialysis bag containing WG-1 silicone segments supported de minimis leaching. Consequently, a 5 log UPEC reduction (99.999% kill) in 24 h using the shake flask test (ASTM E2149) cannot be due to leaching and is ascribed to contact kill. Interestingly, although the MBC was greater than 100 μg/mL for Pseudomonas aeruginosa, WG-1 silicone affected an 80% reduction via a 24 h shake flask test. For other bacteria and Candida albicans, greater than 99.9% shake flask kill may be understood by proposing increased wettability and concentration of charge illustrated in the TOC. De minimis leaching places WG-1 silicone at an advantage over conventional anti-infectives that rely on leaching of an antibiotic or heavy metals such as silver. The facile process for preparation of WG-1 silicone combined with biocidal effectiveness comprises progress toward the goals of device designation from the FDA for WG-1 and clearance.

ANTIMICROBIAL ACTIVITY OF LANTANA CAMARA AGAINST PSEUDOMONAS AERUGINOSA, SERRATIA MARCESCENS AND STAPHYLOCOCCUS AUREUS TO DEVELOP OINTMENT BASED THERAPY

Plant extract (Lantana camara) and earthworm (Pheretima posthuma) extract have been used to treat many illnesses for centuries; they have been reported to suppress the growth of many pathogenic bacteria and are specially used for wound healing. We analyzed the antibacterial activity of the different organic extracts obtained from these species against pathogenic strains of bacteria and compared them to know which is more potent for developing antiseptic ointment. Ethanol and acetone solvents were used for the extraction and analyzed for their antibacterial activity by the disk diffusion and shake flask test. Then we identified the minimum inhibitory concentration of extracts against gram-positive and gram-negative strains. Lantana camara showed the largest growth inhibitory zone against Pseudomonas aeruginosa, followed by Serratia marcescens, and Staphylococcus aureus. MIC for plant extract was 150μg/ml, while earthworm extract inhibited growth at a minimum dose of 200μg/ml. We found that the plant's ethanol extract (L. camara) exhibited robust antimicrobial activity compared to the worm extract. Current investigation reinforces the application of Lantana camara extract to develop ointment to treat wound infections.

Two novel phosphorus/potassium-degradation bacteria: Bacillus aerophilus SD-1/Bacillus altitudinis SD-3 and their application in two-stage composting of corncob residue

For effective utilization of corncob residue to realize green circular production, using composting to obtain a high-quality and low-cost biomass fertilizer has become a very important transformation avenue. In this paper, two novel phosphorus/potassium-degradation bacterial strains were isolated from tobacco straw and identified as Bacillus aerophilus SD-1/Bacillus altitudinis SD-3 (abbreviated as SD-1/SD-3). These identified two novel bacteria SD-1/SD-3 show that the soluble phosphorus content of SD-1/SD-3 reached 360.89mgL-1/403.56mgL-1 in the shake flask test, and the mass concentration of soluble potassium is 136.56mgL-1/139.89mgL-1. In addition, the Laccase (Lac), Lignin peroxidase (LiP), and Manganese peroxidase (MnP) activities of SD-1 and SD-3 are 54.45UL-1/394.84UL-1/222.79UL-1 and 46.27UL-1/395.26UL-1/203.98UL-1 respectively, with the carboxy-methyl cellulase (CMCase) of 72.07UmL-1 and 52.69UmL-1. Meanwhile, the effects of three different combinations of cultures, i.e., no inoculation (K1), inoculation of SD-1/SD-3 on day 21 (K2) and on day 0 (G) are investigated to understand the influence on the degradation degree of corncob residue compost. The results of K2 compost treatment showed that the effective P/K content increased nearly 3.1/2.4 times, the degradation of cellulose/lignin was 49.1/68.0%, and the germination rate was 110.23%, which were higher than other experiment groups K1/G. In conclusion, knowledge of this paper will be very useful for the industrial sector for the treatment of complex corncob residue.

Mechanical, electrochemical, and biological properties of YSZ-Mo: A new class of bio-composites

Polycrystalline tetragonal zirconia (3YTZP) has high strength and fracture toughness (K1C) among the other ceramics. However, this amount is still low compared to metals, limiting the use of these monolithic- parts. This study explores the effect of molybdenum on the mechanical, electrochemical, biological, and antibacterial properties of 3Y-TZP-based composites. Three samples of YSZ, YSZ-10wt.%Mo, and YSZ-20wt.%Mo were fabricated by the SPS method at 1450 °C. The microstructure of the mentioned bio-composites was examined by FESEM and XRD analysis. Three-point flexural strength, fracture toughness test, and Vickers microhardness test were also performed. YSZ-10Mo and YSZ-20Mo samples were subjected to Tafel polarization and electrochemical impedance spectroscopy (EIS) analysis. MTT assay was also used to assess the compatibility of the samples with G-292 cells. The antibacterial behavior of the specimens was assessed by the shake flask test. Microstructural results proved the complete densification of the samples. A rise in the molybdenum content slightly decreased the flexural strength (from 1185 ± 52 MPa for YSZ to 841 ± 63 for YSZ-20Mo) and hardness (from 13.35 ± 0.41 GPa for YSZ to 8.10 ± 0.24 GPa for YSZ-20Mo). However, the opposite behavior was observed for the fracture toughness of the samples (from 7.25 ± 0.67 MPa.m1/2 for YSZ to 14.90 ± 0.32 MPa.m1/2 for YSZ-20Mo). The corrosion test indicated the excellent corrosion resistance of the YSZ-10Mo composite. Enhancement of the molybdenum content had a destructive effect on the corrosion resistance of the composites. The results of the MTT test proved the excellent biocompatibility of the samples. An increment in Mo content also remarkably improved the biocompatibility and antimicrobial activity of the YSZ-20Mo sample.

Mechanism of simultaneous lead and chromium removal from contaminated wastewater by a schwertmannite-like mineral

In this study, a schwertmannite-like mineral was synthesized for the removal of lead (Pb) and chromium (Cr) from contaminated wastewater. A shaking flask test was performed (150 r/min, 1h) with FeSO4·7H2O, H2O2, Na2SiO3, and CaCl2 added for the mineral synthesis reaction. Results show that optimal performance was achieved with the addition of 1.24g/L FeSO4·7H2O, 0.75g/L H2O2, 1.27g/L Na2SiO3, and 0.44g/L CaCl2 at a water temperature of 28°C, with coexisting ion (Na+, K+, Mg2+) concentrations of 1.50mmol/L and 0.50mmol/L EDTA as a complexing agent. Under these optimal conditions, maximum Pb and Cr removal rates of 95.08% and 97.99%, respectively, were achieved within the first 1min of the mineral synthesis reaction, with the synthesis reaction completed by 6min. The simultaneous removal of Pb and Cr during the schwertmannite-like material synthesis process occurred via electrostatic adsorption and coprecipitation. When the concentration of the complexing agent was increased from 0.75 to 6.03mmol/L, the Pb removal rate decreased from 71.88 to 35.45%, and the Cr removal rate decreased from 95.13 to 75.07%, showing that Pb and Cr removal exhibited significant levels of inhibition. In contrast, varying reaction temperatures induced no significant differences. The Pb and Cr dissolution rates from Pb/Cr-containing schwertmannite-like minerals were 8.18% and 2.86% after 40days, respectively. Therefore, the risk of secondary dissolution of heavy metals is small.

Tailings dust characterization and impacts on surface water chemistry at an abandoned Zn-Pb-Cu-Au-Ag deposit

The increased potential for dust mobilization as a result of climate change indicates a need to better understand interactions between dust and water. This research investigates the geochemical effects of tailings dust on surface waters near Stirling mine, Nova Scotia. Tailings were sieved to <63 μm as a proxy for dust and analyzed geochemically and mineralogically for the identification of primary and secondary metal-bearing phases using a scanning electron microscope with automated mineralogy, electron microprobe analysis and synchrotron-based microanalysis. Metal-hosting phases identified include in order of abundance; sphalerite (ZnS), cerussite (PbCO3), chalcopyrite (CuFeS2), Pb–Mn phases (possibly cesàrolite (PbMn3O6(OH)2)), smithsonite (ZnCO3), goethite (FeO(OH), aurichalcite ((Zn,Cu)5(CO3)2(OH)6), hydrohetaerolite (ZnMn2O4·H2O), tennantite (Cu6(Cu4Zn2)As4S12S), and galena (PbS). Shake flask tests were conducted in simulated stream waters (pH = 7) using sieved tailings and passive dry deposition collector filters to investigate the solubility of metal-hosting mineral phases within dust. Results indicate metal leaching at near neutral pH conditions. Sphalerite, cerussite and chalcopyrite are likely the main sources of Zn, Pb, and Cu in the shake flask leachate, based on calculated saturated indices and mass balance. Analyses of stream waters indicate similar conditions (pH, ORP, saturation indices, etc.) compared to the results of the shake flask tests, suggesting they provide reasonable insight about processes occurring in the field. Tailings dust generated at the site is therefore a potential source of metals to surface waters.

Extraction and separation of flavonoids from Malus hupehensis using high-speed countercurrent chromatography based on deep eutectic solvent

In the present experiment, a green and highly efficient extraction method for flavonoids established on deep eutectic solvents (DESs) was investigated by using the response surface methodology. The DES-based high-speed countercurrent chromatography (HSCCC) solvent systems were developed for the separation of high purity compounds from the DES extract of Malus hupehensis for the first time. Under the optimal conditions (liquid-to-solid ratio of 26.3 mL/g, water content of 25.5%, and extraction temperature of 77.5°C), the yield of flavonoids was 15.3 ± 0.1%, which was superior to that of the methanol extraction method. In accordance with the physical property of DES-based HSCCC solvent systems and K values of target compounds, DES-based HSCCC solvent systems composed of choline chloride/glucose-water-ethyl acetate (ChCl/Glu-H2O-EAC, 1:1:2, v/v) was selected for the HSCCC separation. Thus, five flavonoids (two novel compounds 1-2, 6´´-O-coumaroyl-2´-O-glucopyranosylphloretin and 3´´´-methoxy-6´´-O-feruloy-2´-O-glucopyranosylphloretin; three know compounds 3-5, namely, avicularin, phloridzin, and sieboldin) were efficiently separated from Malus hupehensis. DESs are the environment friendly and highly efficient solvents as the components of extraction solvent and HSCCC solvent system, and can be re-utilized many times. However, ethyl acetate can be soluble with a few hydrogen bond donors, such as urea, carboxylic acid and polyol, through the shake flask test. It is the great difficulty for the efficient and rapid separation of target compounds from the DESs extract because of the DESs residual in the HSCCC fractions. ChCl and Glu are the great choices of DESs without this problem. In addition, K values increased with the increase of the molar ratio of ChCl/Glu and the content of water, which could effectively guide us to choose the suitable DES-based HSCCC solvent system. The twice HSCCC separation results indicated that DES was the valuable and green solvent for the HSCCC separation of pure compounds from the extract for the first time, and showed the recycle superiority of DES-based HSCCC solvent system.

Antibacterial cotton with endurance and skin affinity treated by P(DMDAAC-AGE-Si)/(ZnO@CQDs)

The organosilicon quaternary ammonium salt/(zinc oxide@carbon quantum dots) composite material referred to P(DMDAAC-AGE-Si)/(ZnO@CQDs) was prepared with ZnO, glucose and vinyl monomers by situ free-radical polymerization, which was applied into cotton fabrics at different concentrations. It was proved that the antibacterial cotton fabrics had been successfully prepared by FT-IR, SEM, TEM, antibacterial tests (shake flask tests) etc. The antibacterial rate was 98.38% and 99.53% against S. aureus and E. coli, respectively, when the concentration of the treating solution of composites reached to 25 g/L. Even after washing 10 times (equivalent to 50 household washing), the antibacterial rate remained above 89.65% against S. aureus and E. coli. In addition, the hydrophilic properties and air permeability of the treated cotton fabrics were enhanced.

Influence of Sludge Initial pH on Bioleaching of Excess Sludge to Improve Dewatering Performance

pH has an important effect on the physiological activity of eosinophilic microorganisms. Therefore, this study used excess sludge produced by the mixed treatment of leachate and municipal sewage to explore the impact of different sludge initial pH on microbial biochemical reactions associated with the performance of excess sludge dehydration. Shake-flask tests were performed using inoculated microorganisms and fresh excess sludge in 500 mL Erlenmeyer flasks at a ratio of 1:4, with the addition of 2 g/L S0 and 6 g/L FeS2 as energy sources. Erlenmeyer flasks were shaken for 72 h at 180 rpm and 28 °C, in a reciprocating constant homeothermic oscillating water-bath. Results show that the specific resistance to filtration (SRF) of the bioleached excess sludge decreased from (1.45~6.68) × 1012 m/kg to (1.21~14.30) × 1011 m/kg and the sedimentation rate increased from 69.00~73.00% to 81.70~85.50%. The SRF decreased from 1.45 × 1012 m/kg to 1.21 × 1011 m/kg and the sedimentation rate increased from 69.00% to 85.00%, which both reached the highest level when the initial pH of the excess sludge was 5 and the bioleaching duration was 48 h. At this time, the rates of pH reduction and oxidative redox potential (ORP) reached the highest values (69.67% and 515 mV, respectively). Illumina HiSeq PE250 sequencing results show that the dominate microbial community members were Thiomonas (relative abundance 4.59~5.44%), which oxidize sulfur and ferrous iron, and Halothiobacillus (2.56~3.41%), which oxidizes sulfur. Thus, the acidic environment can promote microbial acidification and oxidation, which can help sludge dewatering. The presence of dominant sulfur oxidation bacteria is the essential reason for the deep dehydration of the bioleached sludge.

A rapid and practical prediction method for the Arizona solvent system family used in high speed countercurrent chromatography.

Selecting the appropriate solvent system is the key to the successful separation of samples by using countercurrent chromatography. Although high-speed countercurrent chromatography has been widely used in the separation and preparation of natural products, the selection of a solvent system has always been a stumbling block to the application of high-speed countercurrent chromatography. In order to explore a rapid and practical prediction method to select countercurrent chromatography solvent system, five linear prediction models of the Arizona solvent system family (HEMW) was established by using fourteen compounds with different structures and five HPLC columns of different brands. And two different solvent system selection methods (The partition coefficient K of the target compound in the solvent system was in the range of 0.25<K<2.5) were proposed for targeted separation of compounds and multi-component separation in a complex sample respectively. The appropriate HSCCC solvent system of five known compounds was determined by a HPLC analysis and a shake flask test and the appropriate HSCCC solvent system of two Chinese herbal extracts was determined by a HPLC analysis to verify the prediction method. In this study, solid-liquid partition chromatography (HPLC) and liquid-liquid partition chromatography (HSCCC) were linked by polarity to simplify the screening process of solvent system. This method reduced the difficulty and workload of solvent system selection, which provided methods and ideas for more solvent system prediction models.

SWNTs-PAN/TPU/PANI composite electrospun nanofiber membrane for point-of-use efficient electrochemical disinfection: New strategy of CNT disinfection

Single-walled carbon nanotubes (SWNTs) can be used as 1D electrochemical disinfection material for point-of-use water treatment but are limited by their poor durability and possible cytotoxicity. Immobilizing SWNTs in nanofibers with electrospinning served as slow-release technology develop a novel with a lasting antibacterial and (eco-) toxicological alleviation of SWNTs. Hence, the single-walled carbon nanotubes-polyacrylonitrile/polyurethane/polyaniline (SWNTs-PAN/TPU/PANI, SPTP) composite electrospun nanofiber membrane was successfully fabricated by co-electrospinning process and the electrochemical filtration and disinfection system of point-of-use drinking water treatment is constructed. In the absence of electrolysis, the SPTP filter is effective for complete removal of bacteria by sieving mechanism. Concomitant electrolysis in the course of filtration results in significantly increased inactivation of sieved bacteria. Application of 3.0 V leads to complete (5 log) inactivation of bacteria within 20 min. 5-cycle experiments, membrane flux and shake flask tests prove that composite restrict the excessive release of SWNTs retaining the long-lasting antibacterial properties of SPTP membrane. At 1.0 and 2.0 V, electrolyte concentration and composition is irrelevant to electrochemical inactivation consistent with oxidation of SPTP filter. Bacterial reactive oxygen species (ROSs) also support an oxidation mechanism. At 3.0 V, electrochemical disinfection mainly relies on indirect oxidation.

Development and Application of a Microplate Assay for Toxicity Testing on Aquatic Cyanobacteria.

Regulatory environmental risk assessment, applied to establish a protection limit for all bacterial diversity in surface waters, relies on a growth inhibition test performed on a single species of cyanobacteria and the activated sludge respiration inhibition test. Recently, the ability of this approach to protect adequately for bacteria that provide important ecosystem services has been questioned, and empirical data on additional species to further investigate the effectiveness of the environmental risk assessment are urgently required. We present the development and validation of a cost-effective and time-efficient microplate assay that is comparable to the traditional shake flask test for measurement of cyanobacteria growth rate after chemical exposure. The assay has been optimized to ensure that comparisons of cyanobacteria sensitivity under exponential growth are assessed across equivalent experimental conditions using phycocyanin fluorescence as a surrogate for cell density. The test system is validated using potassium dichromate, and the results are compared with those obtained in an Organisation for Economic Co-operation and Development (2011) test guideline 201 shake flask test system. This assay is suitable for the screening of new and legacy chemicals (including antibiotics) for which ecotoxicology data are lacking across a wide range of cyanobacteria, with the aim of developing more comprehensive environmental risk assessment. Environ Toxicol Chem 2020;39:705-720. © 2019 SETAC.

Experiments and modeling of controlled release behavior of commercial and model polymer-drug formulations using dialysis membrane method.

Standard dissolution testing methods typically do not correlate strongly with the in vivo drug release behavior for the oral delivery products, since they only focus on the drug dissolution in the gastric/intestinal fluid and do not account for the intestinal absorption of drug. Artificial gastrointestinal systems attempt to bridge this gap by using dialysis membranes as a proxy for the intestinal membranes. We present a systematic proof-of-concept study of how the drug dissolution and drug absorption are mimicked in such systems for the case of polymer-drug formulations. We utilize a modified version of the conventional shaking-flask test, in which the drug formulation is placed inside a dialysis bag. Dissolution experiments are performed on a commercial aspirin formulation and model formulations of aspirin with varying amounts of poly-methyl-methacrylate-co-methacrylic acid (PMA-MAA), both for conventional and modified shaking-flask test. Results are successfully interpreted using a simple model that assumes first-order kinetics for both the drug release from the formulation and drug permeation through the membrane. The differences between the model and commercial formulations and the effects of shaking speed and drug loading are established by comparison of the first-order rate constants. Finally, comparison with a reported in vivo study demonstrates how the modified shaking-flask setup can be used to improve the in vitro in vivo correlation. Graphical abstract.

Influence of initial pH on bioleaching of river sediments to achieve deep dehydration.

Acidification is one of the important methods of bioleaching and a rate-limiting steps in the reaction, with initial sediment pH having an important influence on bioleaching efficiency. Therefore, in this study, bioleaching treatments were assessed on river sediments with initial pH ranging from 3.0 to 11.0. Shake-flask tests were performed, using inoculated microorganisms and fresh river sediments in 500mL Erlenmeyer bottles at a ratio of 1:9, with the addition of 5g/L FeS2 and 2g/L S0 as energy sources. Erlenmeyer flasks were shaken for 72h at 180rpm and 28°C, in a homeothermic oscillating water-bath. Results show that the bioleached sediment CST decreased from 39.10s to between 10.3s and 13.0s. Sediment dewaterability reached a maximum level when the initial pH was 5 and the bioleaching duration was 36h, with CST decreasing from 39.10s to 10.30s, a decrease in the CST rate by 82.25%, and moisture content was reduced to 57.5%. Illumina high-throughput sequencing results showed that the relative abundance of dominant microorganisms under different initial pH conditions had no significant difference at the phylum level. However, significant differences were apparent at the genus level. When the initial pH value increased from 3 to 5 in sediments, the relative abundances of the autotrophic bacteria Alicyclobacillus and Ferritrophicum and the heterotrophic bacteria Acidocella, which oxidize S0 and Fe2+, increase and dominate the microbial community, reaching abundances of 8.88%, 5.11%, and 4.87%, respectively. The heterotrophic bacteria Acidocella can biodegrade CLs products and eliminate their inhibitory effect on autotrophic bacteria Alicyclobacillus and Ferritrophicum with this synergistic effect improving the sediment dewatering performance. When the initial pH increased further to 9, the relative abundances of dominant bacteria decreased to varying degrees. In addition, variation in the initial pH conditions had no effect on the elimination efficiencies of pathogenic microorganism which were constantly > 98%. Graphical abstract .

Preparation of antibacterial poly(sulfobetaine methacrylate) grafted on poly(vinyl alcohol)‐formaldehyde sponges and their properties

ABSTRACTConventional wound dressings cover wound surfaces and separate them from the outer environment. However, wound sites are readily infected by some bacteria during healing. To overcome these problems, a macroporous sample is designed through the grafting polymerization of hydrophilic sulfobetaine methacrylate (SBMA) on poly(vinyl alcohol)‐formaldehyde (PVF) sponges. The as‐prepared PVF sponges have a grafting percentage of 15–50%, an average pore size of 60–90 μm, and a high porosity of 90%. This series of PVF‐g‐PSBMA sponges can absorb deionized water and saline solution at approximately 16 g·g−1 within 2 min because of their hydrophilic surface and macroporous structure. The antibacterial potential of PVF‐g‐PSBMA sponges against Escherichia coli and Staphylococcus aureus is evaluated via a shake flask test. As the grafting percentage increase from 15 to 50%, the antibacterial activities against Gram‐positive S. aureus and Gram‐negative E. coli gradually increase from 87 to 95% and from 94 to 99%, respectively. The biocompatibility of these sponges is confirmed through an in vitro cell viability assay. All of the survival rates of the bacterial cells relative to the control (100% of metabolic activity) exceed 90% as the extract ratio of PVF‐g‐PSBMA sponges increase. Thus, the as‐prepared PVF‐g‐PSBMA sponges can be an ideal wound dressing candidate. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47047.

Enhanced degradation of perfluorooctanoic acid by a genome shuffling-modified Pseudomonas parafulva YAB-1

ABSTRACTPerfluorooctanoic acid (PFOA) as an emerging persistent organic pollutant is hard to be degraded by conventional methods because of its stable physical and chemical properties. Microbial transformation is an attractive remediation approach to prevent and clean up PFOA contamination. To date, several strains of wild microbes have been reported to have limited capacity to degrade PFOA, selection of superior strains degrading PFOA become urgently necessary. Here, we report the application of genome shuffling to improve the PFOA-degrading bacterium Pseudomonas Parafulva YAB-1. The initial mutant populations of strain YAB1 were generated by nitrosoguanidine and ultraviolet irradiation mutagenesis respectively, resulting in mutants YM-9 and YM-19 with slightly improved PFOA-degrading ability. YM-9 and YM-19 were used as the starting strains for three rounds of recursive protoplast fusion. The positive mutants were screened on inorganic salt medium plates containing different concentrations of PFOA and selected based on their PFOA degradability in shake-flask fermentation test. The best performing recombinant F3-52 was isolated after three rounds of genome shuffling. In batch fermentation, the PFOA degradation rate of mutant F3-52 was up to 58.6%, which was 1.8-fold higher than that of the parent strain YAB1, and 1.6-fold higher than the initial mutants YM-9 and YM-19. Pass-generation test indicated that the heredity character of F3-52 was stable. The results demonstrated that genome shuffling was an efficient method for improving PFOA degradation of Pseudomonas Parafulva YAB1. The bred mutant F3-52 with 58.6% PFOA-degrading rate could be used for the environmental control of PFOA pollutant.

The evaluation of the in vitro antimicrobial properties of fibers functionalized by chitosan nanoparticles

In this work, chitosan (CS) and its water-soluble derivatives, N,N,N-trimethyl chitosans (TMC), were used in the form of solution and nanoparticles dispersions (CSNP) as an adsorbate for cellulose fibers in order to obtain bioactive functionality of fibers aimed toward use in tampons. To examine the usability of bioactive tampons it is extremely important to provide detailed information about tampons’ antimicrobial capacity regarding pathogen microorganisms (MOs), as well as for those responsible for healthy flora such as Lactobacillus sp. Thus, evaluation of the in vitro antimicrobial properties of functionalized fibers was performed in detail using the standard shake-flask test method (ASTM E2149) and “time-kill” method (non-standard method) against S. aureus, E. coli, and C. albicans. Both methods were compared. Susceptibility of Lactobacillus sp. to coated fibers was tested as well. Additionally, cytotoxic properties of fibers were evaluated as a further indicator of safety aspect of tampons functionalized by CS and TMC. The results show that specific functionalization of tampons using CS nanoparticles could improve tampon antimicrobial activity and offer a safety upgrade for the regular feminine cotton tampon, providing an attractive feature.

A facile antibacterial coating based on UV-curable acrylated imidazoliums

Using ultraviolet (UV)-curable 3-(2-(methacryloyloxy)ethyl)-1-alkyl imidazoliums with different alkyl substituents as the bactericidal monomers and trimethylolpropane triacrylate as the crosslinker, highly efficient antibacterial coatings were designed and facilely prepared by a one-step UV-curing method. The differential photocalorimetry experiment showed these monomers polymerized within 120 s under UV irradiation, indicating a very good curable property. The excellent antibacterial activity of these coatings, which reached up to 99.8% ratio against Escherichia Coli, was demonstrated by a shake flask test method.