Shake Flask Test Research Articles

Aerobic biodegradation of nonylphenol ethoxylates in shaking-flask test

Nonylphenol ethoxylates (NPEOs), which are widely used for industrial and domestic purposes, exert adverse effects on wildlife after being used and discharged into the environment. However, their ultimate biodegradability and biodegradation pathway remains unclear. In this study, the aerobic degradability of nonylphenol ethoxylates (NPEOs) by the acclimated microorganisms in active sludge was examined using shaking-flask tests. The degradation of benzene rings in NPEOs was determined using UV spectroscopy and high performance liquid chromatography (HPLC). Results showed that more than 80% of benzene rings were removed after 8-10 days of degradation, and the majority of NPEOs were also removed after 9 days of degradation, indicating NPEOs and the benzene rings could be ultimately degraded by microorganisms in acclimated active sludge. Electrospray ionization-mass spectroscopy (ESI-MS) analysis of biodegradation intermediates indicate that stepwise omega, beta-oxidation of EO chains or fission of EO chains, and further omega, beta-oxidation of alkyl-chain for short-EO-chain NPEOs constitute the main pathway in the early stage, and complete biodegradation occur when the benzene rings in these molecules are opened in the later stage. Normal 0 21 false false false ES-CL X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Tabla normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

EVOH-based nanocomposites prepared by simple saponification method

The nanocomposite powders of poly(ethylene-co-vinyl alcohol)/Na+-montmorillonite (EVOH/MMT) and EVOH/Loess were prepared by a solution-precipitation and saponification method. EVA/toluene/nanoclay suspensions were precipitated and saponified in ethanol/KOH solution in a heterogeneous manner. Tensile properties, morphology, and thermal behavior of the prepared nanocomposites have been evaluated using UTM, SEM, and DSC, respectively. The tensile strength and elongation at break of EVA/MMT-50% and EVA/Loess-50% nanocomposites were significantly increased up to 1 h saponification time and thereafter gradually decreased. At 1 h saponification time, the tensile strength of EVA/ Loess-50% nanocomposite was increased by 5.4-fold to 14.7 MPa, whereas EVA/MMT-50% increased the tensile strength by 2.2-fold to 10.4 MPa compared to the un-saponified one. With the increase in saponification time, melting and crystallization peak temperature of both nanocomposites was shifted at a higher temperature. The antibacterial activity of saponified EVA/MMT-50% and EVA/Loess-50% powders was also determined by shake flask test against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Among the nanocomposites used in this study, EVA/MMT-50%-6 h exhibited strong antibacterial activity against the two kinds of bacteria.

Chitosan derivatives with dual-antibacterial functional groups for antimicrobial finishing of cotton fabrics

The three water-soluble chitosan derivatives bearing double functional groups were synthesized with 2,3-epoxypropyltrimethylammonium chloride and benzaldehyde as modifiers through formation of Schiff base, reduction, N-methylation and O-quaternization. The synthesized chitosan derivatives were applied to cotton fabrics together with citric acid (CA) as the crosslinking agent to evaluate their use as durable antimicrobial textile finishing agents. The optimal finishing conditions were investigated and antibacterial activities of finished fabrics were tested with “Shake-Flask Test”. The fabrics finished showed strong antimicrobial activities and fairly good durability. The antibacterial efficiency of S. aureus and E. coli was more than 99% and 96% respectively, when crosslinked with CA (14%, o.w.f) through a two-bath process. The order of antimicrobial activities of the chitosan derivatives was O-quaternized-N,N-biethyl-N-benzyl ammonium chitosans chloride (O-QCTS-DEBn) ≥ O-quaternized-N-chitosan Schiff bases (O-QCTSS) > O-quaternized-N-benzyl-chitosans (O-QCTS-Bn). The antibacterial activity of using O-QCTSS finishing fabric was still more than 75% after 20 consecutive home launderings.

Melt Production and Antimicrobial Efficiency of Low-Density Polyethylene (LDPE)-Silver Nanocomposite Film

Colloidal silver nanoparticles with a size of 5.5 ± 1.1 nm were prepared by chemical reduction using polyethylene glycol (PEG). Silver nanoparticles were incorporated into low-density polyethylene (LDPE) by melt blending and subsequent hot pressing at 140 °C to produce nanocomposite film with an average thickness of 0.7 mm. PEG was added at 5% weight of polymer as a compatibilizer agent in order to prevent agglomeration and provide uniform distribution of nanoparticles in polymer matrix. Antimicrobial activity of silver nanocomposites against Escherichia coli ATCC 13706, Staphylococcus aureus ATCC12600, and Candida albicans ATCC10231 was evaluated by semi-qualitative agar diffusion test and quantitative dynamic shake flask test. Mechanical properties of nanocomposites were not significantly different from silver-free LDPE-containing PEG films (p > 0.05), and silver nanoparticles did not form chemical bonding with the polymer. LDPE-silver nanocomposite samples by more than 6.69 ppm silver nanoparticles showed considerable antimicrobial clear zone. LDPE-silver nanocomposite affected growth kinetic parameters of the examined bacteria and is more efficient on S. aureus than E. coli. Polyethylene-silver nanocomposites containing 22.64 ppm silver nanoparticles could reduce 57.8% growth rate and 23.3% maximum bacterial concentration and increase 35.8% lag time of S. aureus. This study shows the potential use of LDPE-silver nanocomposite as antimicrobial active film. Antimicrobial efficiency of silver nanocomposite depends on silver nanoparticles concentration; however, high level of silver nanoparticles may lead to weakening of mechanical properties.

Structure, Thermal, and Antibacterial Properties of Polyacrylonitrile/Ferric Chloride Nanocomposite Fibers by Electrospinning

In the present work, the manufacturing of pure polyacrylonitrile (PAN) nanofiber and PAN/FeCl3 nanocomposite fibers was explored by an electrospinning process. The effects of FeCl3 on the structure, thermal stability, and antibacterial properties of the PAN nanocomposite fibers were studied, and were respectively characterized by scanning electron microscopy (SEM), thermogravimetric analyses (TGA), and shake flask tests. The SEM images showed that the diameters of nanocomposite fibers decreased with the loading of FeCl3. The TGA analyses revealed that the onset temperature of thermal decomposition, maximum decomposition temperature, and amount of charred residue at 700°C of PAN nanocomposite fibers was notably increased in the presence of FeCl3, contributing to improved thermal stability properties. It was also found that the reduction percentage of the tested bacteria, Escherichia coli, reached 87% when the FeCl3 content was 5 wt.% of the PAN nanocomposite fibers.

Study of the Morphology and Antibacterial Properties of Nano Silver Films Prepared on Regenerated Cellulose Substrate

Nano size silver films were deposited on the surface of regenerated cellulose films by magnetron sputtering, to impart antibacterial functionality to the cellulose films. Field emission scanning electron microscopy (FESEM) images revealed that the silver films were composed of nano size compact grains and the surface shape of the grains changed with changing sputtering power. As the power increased, the size of the nano silver grains increased and the number of grains decreased. Surface elemental analysis by energy dispersive spectrometry (EDS) showed a small amount of elemental silver on the surface. The antibacterial activity of the films was assessed by the shake flask test which measured the number of Staphylococcus aureus bacteria. The percentage reduction of the bacteria reached >99.9%.

Biodegradability, antibacterial properties, and ultraviolet protection of polyvinyl alcohol‐natural polyphenol blends

AbstractPolymer films of tea polyphenol (TP)/polyvinyl alcohol (PVA) were prepared by a solution casting. The films were studies for intermolecular interactions by Fourier transform infrared spectroscopy, the shifts in the major signals of IR for OH and CO absorption, and with varied intensities in the Fourier transform infrared spectroscopy spectra indicated intermolecular hydrogen bonded interaction between PVA and TP. The biodegradability of the PVA/TP blends is measured by soil burial test, the percentage weight loss of the PVA/TP blends increased with increasing TP content. And the antibacterial activity of PVA/TP blends was determined by shake flask test and three kinds of bacteria used were as follows: Staphylcoccus aures, Escherichia coli, and Proteus valgaris. The blends exhibit strong antibacterial activity against the three kinds of bacteria. According to the Australia/New Zealand standard, AS/NZS 4399:1996, the ultraviolet protective properties of the PVA/TP blends were evaluated and the result shows that the capacity of the ultraviolet protection for blends was extremely increased by adding TP to PVA. And all blends reach the highest level (50+) of the standard. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Antibacterial properties of PLA nonwoven medical dressings coated with nanostructured silver

In this paper, magnetron sputtering was applied to deposit nano-structured silver films on the surfaces of polylactic acid (PLA) nonwovens, which were used in medical dressings. The influence of the coating thickness of the nano-structured sliver films on the antibacterial property of the nonwovens was studied. The antibacterial properties of the medical dressings were measured by shake flask test. The surface morphology of nano-structured silver films and the grain sizes of silver agglomerates were analyzed by atomic force microscope (AFM). Energy dispersive X-ray (EDX) was employed to analyze the surface elemental compositions. The study revealed that the antibacterial properties were improved as the film thickness increased. AFM images of the coated samples indicated that as the sputtering time prolonged, the film thickness was increased, the film became compacter, and the specific area of the film was also increased. Thus, the release rate of silver ions increased, leading to the improved antibacterial property. It was found that the reduction percentage of both tested bacteria-Staphylococcus aureus and Escherichia coli reached 100 % as the coating thickness exceeded 1 nm.

Improved Production of Biosurfactant with Newly Isolated Pseudomonas aeruginosa S2

An indigenous strain Pseudomonas aeruginosa S2 (P. aeruginosa S2), isolated from diesel-contaminated soil, produced extracellular surface-active material identified as rhamnolipid. Due to its excellent surface activity, rhamnolipid is known to be well-suited for stimulating the bioremediation efficiency of oil contaminated sites. To improve production yield of rhamnolipid with P. aeruginosa S2, various carbon and nitrogen sources were screened to select favorable ones leading to better biosurfactant production yield. It was found that using 4% glucose could attain better rhamnolipid yield, while 50 mM NH4NO3 appeared to be the most preferable nitrogen source. Meanwhile, the effect of carbon to nitrogen ratio (C/N ratio) on rhamnolipid yield was also investigated, and the optimal C/N ratio was identified as approximately 11.4. Moreover, response surface methodology (RSM) was applied to optimize the trace element concentration for rhamnolipid production. Results from two-level design indicate that concentrations of MgSO4 and FeSO4 were the most significant factors affecting rhamnolipid production. Using steepest ascent method and RSM analysis, an optimal medium composition was determined, giving a rhamnolipid production yield of 2.37 g/L in 100 h at 37 degrees C and 200 rpm agitation. Scale-up production of rhamnolipid in a well-controlled 5 L jar fermentor using the optimal medium and operating condition (at 37 degrees C and pH 6.8) further elevated the biosurfactant production yield to 5.31 g/L (in 97 h), which is over 2-fold higher than the best results obtained from shake-flask tests.

Heterogeneous photo-Fenton oxidation of benzoic acid in water: Effect of operating conditions, reaction by-products and coupling with biological treatment

The heterogeneous photo-Fenton oxidation of benzoic acid, a precursor of several organic pollutants found in agro-industrial effluents, was studied in model aqueous solutions. UVA irradiation was provided by a 125W medium pressure mercury lamp, while a nanocomposite material of crystalline iron oxides supported over mesostructured SBA-15 was used as the catalyst. Experiments were conducted at benzoic acid initial concentrations between 25 and 450mg/L, catalyst concentrations between 0.3 and 1.2g/L and hydrogen peroxide concentrations between 20% and 100% of the stoichiometric amount needed for complete mineralization. Conversion, which was found to be first order regarding benzoic acid concentration, generally increased with increasing the concentration of Fenton's reagents and decreasing substrate concentration. HPLC analysis showed that oxidation was accompanied by the formation of several by-products; of these, the three monohydroxybenzoic acids as well as oxalic acid were successfully identified and quantified. By-products were more resistant to oxidation than benzoic acid since COD reduction was generally lower than substrate conversion. Catalyst stability was assessed measuring the extent of iron leaching in the reaction mixture and was found to be excellent as dissolved iron never exceeded 5% relative to the initial iron content. The aerobic biodegradability of benzoic acid before and after photo-Fenton oxidation was assessed by shake flask tests. Chemical oxidation enhanced the biodegradability of benzoic acid although the oxidized solution was more ecotoxic to marine bacteria than the original one. The feasibility of coupling chemical and biological oxidation was also assessed for an actual olive oil mill effluent.

Silver‐embedded granular activated carbon as an antibacterial medium for water purification

AbstractSilver (Ag) particle embedded granular activated carbon (GAC) was made for the first time to assess its ability in inhibiting the growth of Escherichia coli (E. coli), a water‐borne bacterial pathogen. Ag‐GAC was made by impregnating GAC with AgNO3 and then reducing it to metallic Ag. Plate assay showed slight inhibition of E. coli, even with Ag‐GAC prepared from 0.005 mol L−1 AgNO3, but this and shake flask tests showed a conspicuous effect only for higher concentrations of 0.1–1 mol L−1 AgNO3. Flow tests further indicated that Ag‐GAC made from 1.0 mol L−1 AgNO3 caused a desirable three orders of reduction in E. coli number concentration in less than 30 s. An optimum of 9–10.5 wt% of embedded Ag in the final Ag‐GAC product was necessary for the requisite complete inhibition of E. coli, killing bacteria in the contact‐mode for up to 350 L of flowing water. These results prove that Ag‐GAC possesses antibacterial properties and can be used for disinfection to produce potable quality water. Copyright © 2008 Society of Chemical Industry

Sputter deposition of nanostructured antibacterial silver on polypropylene non-wovens

Nanostructured silver films were deposited at room temperature on polypropylene non-wovens by radio frequency magnetron sputter coating to obtain the antibacterial properties, and the relationship between sputter parameters and antibacterial properties were investigated in this paper. The antibacterial activity of the materials was assessed using shake flask test. The effects of silver film deposition on surface morphology were characterised using SEM and AFM. Surface elemental compositions were also analysed using EDX analysis. The results of antibacterial tests revealed that deposition time was the key parameter affecting the antibacterial properties of the materials, while sputtering power and argon pressure seemed to have a slight effect on antibacterial performance. It is believed that the total amount of silver ions released from the silver coating was increased as the deposition time increased. The AFM images and quantitative analysis by EDX respectively revealed that increase in deposition time led to the increased coverage of silver film and the increased silver weight percentage per unit surface, which provided evidences for the increased release rate of the silver ions from coating.

Photocatalytic treatment of black table olive processing wastewater

The photocatalytic treatment of an effluent from black table olive processing over TiO 2 suspensions was investigated. The study focused on the effect of various operating parameters on the treatment efficiency including initial organic load, catalyst type, concentration and reuse, and addition of hydrogen peroxide. Initial organic load, expressed in terms of chemical oxygen demand (COD), was studied in the range 1–8 g/L, anatase TiO 2 concentrations in the range 0.25–2 g/L and H 2O 2 concentrations in the range 0.025–0.15 g/L. Treatment efficiency, which was assessed in terms of COD, total phenols, aromatics and color reduction, generally increased with decreasing initial COD and increasing contact time, catalyst and H 2O 2 concentrations; however, for H 2O 2 there was a maximum dosage above which performance deteriorated. Depending on the conditions employed, nearly complete decoloration (>90%) could be achieved, while mineralization never exceeded 50%. Shake-flask tests with non-acclimated activated sludge showed that both the original and photocatalyzed effluents were degradable aerobically with the biodegradation rate of the original effluent being three times greater than the oxidized one. On the other hand, photocatalytic oxidation of the original effluent was at least two orders of magnitude faster than its biological oxidation to achieve comparable levels of degradation.

NANOSTRUCTURED ANTIBACTERIAL SILVER DEPOSITED ON POLYPROPYLENE NONWOVENS

Nanostructured silver films were deposited on polypropylene (PP) nonwovens by RF magnetron sputter coating to obtain the antibacterial properties. Shake flask test was used to evaluate the antibacterial properties of the materials. Atomic force microscope (AFM) was utilized to observe the surface morphology. Energy-dispersive X-ray (EDX) was also employed to analyze the surface elemental compositions. The antibacterial results indicated that the prolonged deposition time led to a significant improvement in antibacterial effect, and sputtering power and argon pressure did not show obvious effect on antibacterial performance. It is believed that the total amount of silver ions released from the silver coating was increased as the deposition time increased. AFM images and quantitative analysis of EDX, respectively revealed that increase in deposition time led to the increased coverage of silver film and the increased silver weight percentage per unit surface, which provided evidences for the increased release rate of silver ions from the coating. Moreover, it was found that the optimum silver coating thickness was about 3 nm, taking antibacterial effect and cost of production into account.

Photocatalytic treatment of wastewater from cottonseed processing: Effect of operating conditions, aerobic biodegradability and ecotoxicity

The heterogeneous and homogeneous UV-A photocatalytic treatment of an acidic waste stream originating from cottonseed processing was investigated. Several TiO 2 samples were screened in heterogeneous slurry experiments and a commercially available TiO 2 anatase (Millennium PC 500) was found to be considerably more active than the rest. The effect of key operating conditions such as effluent dilution (COD from 800 to 8000 mg/L), Millennium TiO 2 loading (from 100 to 1500 mg/L), solution pH (from 2.6 to 10) and the water matrix (presence of effluent solids and dissolved oxygen) on treatment efficiency was also studied. In general, degradation decreased with increasing effluent concentration, increasing solution pH from acidic to neutral and alkaline conditions and in the absence of oxygen serving as electron acceptor. Experiments with 500 mg/L TiO 2 for 240 min led to nearly complete mineralization at 800 mg/L initial COD but higher catalyst loadings suppressed degradation. Homogeneous experiments with 100 mg/L Fe 2+ or Fe 3+ were also performed leading to about 50% COD reduction; this increased to about 65% when H 2O 2 was added, i.e. simulating a Fenton reaction. The original, un-treated effluent was very toxic to marine bacteria Vibrio fischeri and very slowly biodegradable aerobically as assessed by shake-flask tests. Nonetheless, a 10-fold dilution (i.e. 800 mg/L COD) eliminated completely ecotoxicity and improved substantially biodegradation rates. On the other hand, photocatalytically pre-treated samples were less biodegradable than the un-treated one. Deep photocatalytic oxidation resulted in decreased ecotoxicity to V. fischeri, while moderate photocatalytic oxidation increased toxicity probably due to the formation of toxic intermediates.

Preparation and characterization of silver nanocomposite textile

Nanostructured silver films of different thicknesses were deposited on surfaces of polypropylene nonwovens by magnetron sputter coating to obtain antibacterial and electrical conductive properties. The surface morphology of nanostructured silver films was investigated by atomic force microscopy (AFM). The antibacterial properties of the nonwovens coated with relatively thinner films were evaluated using the shake flask test. The conductivity of the nonwovens coated with relatively thicker films was examined using an ohm-meter. The results of the antibacterial test revealed that the antibacterial performance improved gradually as the film thickness increased from 0.5 to 3 nm. It is believed that the total amount of silver ions released from the coating was increased along with the increase in film thickness. As sputtering time prolonged, the grain sizes of the silver particles were increased and the coating became more compact. The results of the electrical conductivity test showed that the increased film thickness led to the improved electrical conductivity when the film was relatively thicker. The AFM images clearly revealed the change in surface morphology formed by sputter coating. The growth and coverage of the coating layer contributed to the improvement in its antibacterial and conductive properties.

Bacterial heap-leaching: Practice in Zijinshan copper mine

Zijinshan copper mine is the largest chalcocite deposit in China. The attempt to recover copper from the ore by bioleaching began at the end of 1998. Following the metallurgical studies carried out over 2 years, a pilot plant consisting of bio-heap leaching and SX–EW was built at the Zijinshan Copper Mine at the end of 2000, with a production capacity of 300 t/a copper cathode. After its successful operation for 1.5 years, the plant was scaled up to a capacity of 1000 t/a copper cathode by June 2002. Currently a commercial bio-heap leach plant with a capacity of 10,000 t/a is under construction and is scheduled to be commissioned by the end of 2005. This paper describes metallurgical studies and pilot plant tests for Zijinshan Copper ore. A brief introduction to the mineralogy, bacterial culture, shake flask tests and column tests on bioleaching is presented. The performance of bio-heap leaching and SX–EW, acid and iron balance, operational cost of the pilot plant are discussed. A brief summary of the process flow sheet and the estimated capital cost of the commercial plant of 10,000 t/a are presented at the end of the paper.

Mechanical Properties and Antimicrobial Activity of Silicone Rubber Compounds Containing Acrylated Norfloxacin and Its Polymer

AbstractSummary: Antibacterial silicone rubbers (SR) were prepared by platinum curing and peroxide curing of a silicone compound containing the synthetic antimicrobial monomer 1‐ethyl‐6‐fluoro‐7‐{4‐[2‐hydroxy‐3‐(2‐methylacryloyloxy)‐propyl]piperazin‐1‐yl}‐4‐oxo‐1,4‐dihyroquinoline‐3‐carboxylic acid (MQ) and its polymer PMQ. The effects of the two curing systems on the mechanical properties were compared. Tensile strength and elongation at break of the platinum‐cured SR decreased with increasing concentrations of MQ and PMQ. For the peroxide curing system, the elongation at break increased with increasing concentrations of the antimicrobial agents. The antibacterial activity of the prepared SR was examined by the shake flask test against Staphylococcus aureus and Escherichia coli, which are representative of Gram‐positive and Gram‐negative bacteria, respectively. All compounds showed excellent antibacterial activities against these two types of bacteria.Structure of acrylated norfloxacin.magnified imageStructure of acrylated norfloxacin.

Photocatalytic and sonolytic oxidation of acid orange 7 in aqueous solution

The oxidation of 50mg/L azodye acid orange 7 (AO7) in water was investigated by means of photocatalysis in the presence of various semiconducting catalysts and ultrasound irradiation. The UVA-induced photocatalytic degradation over TiO2 anatase suspensions was found to increase with increasing catalyst concentration, decreasing solution pH, as well as in the presence of dissolved oxygen. The presence of 1,4-benzoquinone, sodium azide or sodium chloride in the reaction mixture decreased degradation due to the scavenging of radicals and other reactive moieties. Interestingly, addition of hydrogen peroxide at various concentrations from 21 to 1050mg/L also inhibited degradation. The sonochemical degradation of AO7 was found to increase with increasing frequency and decreasing temperature. Under similar treatment conditions, ultrasound irradiation resulted in higher conversion than photocatalysis; moreover, the sonochemically irradiated solution consistently contained low aliphatic intermediates, while the photocatalytically treated solution mainly consisted of aromatic intermediates as confirmed by GC–MS analysis. The acute toxicity to marine bacteria V. fischeri decreased following oxidation with either process. Furthermore, deep sonochemical treatment slightly improved the aerobic biodegradability as assessed by shake flask tests.

Antibacterial activity of polymers with norfloxacin moieties against native and norfloxacin‐tolerance‐induced bacteria

AbstractAntimicrobial characteristics were investigated for norfloxacin against 18 bacteria (4 gram‐positive bacteria and 14 gram‐negative bacteria) with the minimum inhibition concentration (MIC) test. Among the bacteria tested, B. cereus, V. fluvialis, and V. parahaemolyticus formed norfloxacin‐tolerant colonies. The release of ultraviolet‐absorbing substances from the cells in contact with norfloxacin was examined for the native bacteria and for the norfloxacin‐tolerance‐induced ones. Norfloxacin was grafted to polypropylene‐graft‐maleic anhydride (MAPP) and poly(styrene‐co‐maleic anhydride) (MAPS) to synthesize polymeric antimicrobial agents. The bioactivity of MAPP–norfloxacin and MAPS–norfloxacin was evaluated and compared with that of neat norfloxacin with the shake flask test and the MIC test. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 936–943, 2005