Effect of cationic surfactant cetyltrimethylammonium bromide on the enzymatic hydrolysis of cellulose

Effect of cationic surfactants alkyltrimethylammonium bromide (C_nTAB) with varied alkyl chain lengths on the enzymatic hydrolysis of Avicel and the surface charge of cellulase was investigated. Enzymatic hydrolysis of Avicel increased linearly from 42.1 to 61.4 % with the increase of the concentration of cetyltrimethylammonium bromide (C₁₆TAB) logarithmically from 0.0001 to 0.01 mM, and reached a maximum value at the concentration of 0.01–0.03 mM. When the concentration was increased further, the cellulase solution became positively charged and the enzymatic hydrolysis of Avicel decreased rapidly. With the increasing alkyl chain length, C_nTAB provided more proton and neutralized the negative charge of cellulase more obviously. Therefore, the required concentration of C_nTAB could be less to enhance the enzymatic hydrolysis of Avicel. In addition, C₁₆TAB could enhance enzymatic hydrolysis efficiency of corncob at high solid content from 35.0 to 56.3 %; C₁₆TAB could reduce about 60 % of the cellulase loading in the enzymatic hydrolysis of corncob to obtain the same glucose yield. Effect of C₁₆TAB on the enzymatic hydrolysis of typical pretreated softwood and hardwood was also investigated. This study laid the foundation for using C_nTAB to recover cellulase, and provided the design direction for cellulase with higher activity and better stability by adjusting its hydrophilicity and chargeability.     

Electrophoretic properties of complexes between DNA and the cationic surfactant cetyltrimethylammonium bromide

We use agarose gel electrophoresis to characterize how the monovalent catioinic surfactant cetyltrimethylammonium bromide (CTAB) compacts double-stranded DNA, which is detected as a reduction in electrophoretic DNA velocity. The velocity reaches a plateau at a ratio R = 1.8 of CTAB to DNA-phosphate charges, i.e., above the neutralization point, and the complexes retain a net negative charge at least up to R = 200. Condensation experiments on a mixture of two DNA sizes show that the complexes formed contain only one condensed DNA molecule each. These CTAB-DNA globules were further characterized by time-resolved measurements of their velocity inside the gel, which showed that CTAB does not dissociate during the migration but possibly upon entry into the gel. Using the Ogston-model for electrophoresis of spherical particles, the measured in-gel velocity of the globule is quantitatively consistent with CTAB having two opposite effects, reduction of both the electrophoretic charge and DNA coil size. In the case of CTAB the two effects nearly cancel, which can explain why opposite velocity shifts (globule faster than uncomplexed DNA) have been observed with some catioinic condensation agents. Dissociation of the complexes by addition of anionic surfactants was also studied. The DNA release from the globule was complete at a mixing ratio between anionic and cationic surfactants equal to 1, in agreement with equilibrium studies. Circular DNA retained its supercoiling, and this demonstrates a lack of DNA nicking in the compaction-release cycle which is important in DNA transfection and purification applications.     

Influence of the fluoride ion on the aggregation and catalytic properties of micellar solutions of cetyltrimethylammonium bromide

The influence of the fluoride ion on the aggregation behavior and catalytic properties of neutral and alkaline aqueous solutions of cetyltrimethylammonium bromide in nucleophilic substitution reactions of phosphorus acid esters was studied by tensiometry, small-angle neutron scattering, and UV spectrophotometry. The critical micelle concentrations and the radii, aggregation numbers, and shape of micelles forming in these systems, as well as the kinetic parameters of the nucleophilic substitution reactions of phosphorus acid esters, were determined.     

Interaction of quinapril anion with cationic surfactant micelles of cetyltrimethylammonium bromide

In this study, the interaction of the anion of quinapril (QUIN), angiotensin converting enzyme (ACE) inhibitor, with cationic surfactant cetyltrimethylammonium bromide (CTAB) was investigated. The effect of cationic micelles on the spectroscopic and acid-base properties of QUIN was studied at pH 8. The binding of QUIN anion to CTAB micelles implied a shift in drug acidity constant (pK(a)(water)-pK(a)(micelle)=1.39) proving the great affinity of negatively charged QUIN ion for the positively charged CTAB micelle surface. The strong dependence of the partition coefficient K(x) on QUIN concentration, obtained by using pseudo-phase model, is consistent with an adsorption-like phenomenon. From the dependence of differential absorbance at lambda=272 nm on CTAB concentration, by using mathematical model that treats the solubilization of QUIN anion as its binding to specific sites in the micelles (Langmuir adsorption isotherm), the binding constant K(b)=(2.3+/-0.4)x10(3) mol(-1)dm(3) was obtained. QUIN-CTAB binding constant was also calculated from micellar liquid chromatography (MLC) and this method was found to be not accurate enough for its determination.     

Polarographic behavior of nicotinamide in surfactant media and its determination in cetyltrimethylammonium bromide surfactant system

The behavior of nicotinamide has been studied by differential pulse polarography and cyclic voltammetry in the presence of certain ionic and nonionic surfactants, viz. cetyltrimethylammonium bromide (CTAB), sodium dodecylsulfate (SDS) and Triton X-100 (TX-100). The cathodic peak potential (E(p(c))) and peak current (I(p(c))) of nicotinamide were found to be remarkably dependent on the charge and concentration of the surfactant. The presence of SDS and that of TX-100 cause a shift in peak potential and a change in peak current of nicotinamide. In the presence of the cationic surfactant, CTAB, an enhancement in the sensitivity of nicotinamide was observed. A sharp peak with more than two-fold increase in current was used to determine the limit of detection and linear working range using the differential pulse polarographic technique. The present method was successfully used for the simultaneous determination of nicotinamide and pyridoxine hydrochloride, and for the determination of nicotinamide in multivitamin pharmaceutical preparations.     

Effect of sodium dodecyl sulfate and cetyltrimethylammonium bromide catanionic surfactant on the enzymatic hydrolysis of Avicel and corn stover

Nonionic surfactants could effectively improve the enzymatic hydrolysis efficiency of lignocellulose, while small molecule anionic and cationic surfactants usually inhibited the enzymatic hydrolysis. The results showed that the anionic surfactant sodium dodecyl sulfate (SDS) could improve the enzymatic hydrolysis efficiency of Avicel at the concentration range of 0.1–1 mM, but it did inhibit enzymatic hydrolysis at higher concentration. Cationic surfactant cetyltrimethylammonium bromide (CTAB) was used to regulate the surface charge of SDS; thereby catanionic surfactant SDS-CTAB was formed. The effect of SDS-CTAB catanionic surfactant with varied molar ratios on the enzymatic hydrolysis of pure cellulose and corn stover at various enzymatic hydrolysis environments was investigated. SDS-CTAB could increase the enzymatic hydrolysis of corn stover at high solid loading from 33.3 to 42.4%. Using SDS-CTAB could reduce about 58% of the cellulase dosage to achieve 80% of the enzymatic hydrolysis of corn stover. SDS-CTAB catanionic surfactant could regulate the surface charge of cellulase in the hydrolyzate and reduce the non-productive adsorption of cellulase on the lignin, thereby improving the enzymatic hydrolysis efficiency of lignocellulose.     

Langmuir aggregation of Evans blue on cetyltrimethylammonium bromide and on proteins and its application

The microphase adsorption-spectral correction (MPASC) technique is described and applied to the study of the interactions of Evans blue (EB) with cetyltrimethylammonium bromide (CTAB) and with four proteins: bovine serum albumin (BSA), myoglobin (Mb), hemoglobin (Hb) and ovalbumin (OVA). EB can be adsorbed on a cationic surfactant and on protein by electrostatic force and the aggregation obeys the Langmuir isotherm. Results have shown that the products are formed as follows: monomer aggregate EB·CTAB, micellar aggregate (EB·CTAB)₇₈ and protein aggregates (EB₆₈·BSA), (EB₁₄·OVA), (EB₁₂₆·Mb) and (EB₅₈·Hb). The adsorption constant of the aggregates are calculated to be K_EB·CTAB=2.95×10⁶, K_EB68·BSA=3.40×10⁴, K_EB14·OVA=5.20×10², K_EB126·Mb=6.81×10² and K_EB58·Hb=5.73×10², respectively. The aggregation of EB in proteins is sensitive in the presence of CTAB and selective in the presence of EDTA and it has been applied to the analysis of samples with satisfactory results.     

Effect of cetyltrimethylammonium bromide addition on the emulsions stabilized by montmorillonite

The wettability of montmorillonite could be in situ modified by cationic surfactant cetyltrimethylammonium bromide (CTAB). The type and stability of emulsions prepared from montmorillonite with different concentrations of cationic surfactant were investigated, and a double phase inversion of emulsions was observed. The adsorption of CTAB on montmorillonite particles was studied by surface tension and zeta potential measurements, and the variation of the wettability of particles with the concentration of CTAB was characterized by the contact angle measurements. The adsorption of particles at the surface of emulsion droplets was observed by laser-induced confocal scanning microscopy. At low surfactant concentrations, the adsorption of CTAB on montmorillonite increased the hydrophobicity of the particles, and the stability of oil-in-water emulsions was enhanced. With the increase of the CTAB concentration, montmorillonite particles changed from hydrophilic to hydrophobic, and water-in-oil emulsions were obtained. However, at higher surfactant concentrations, the emulsions inverts to O/W again because montmorillonite particles were reconverted into hydrophilic due to the formation of CTAB bilayer on the surface of montmorillonite.     

Phase behavior of DNA in the presence of cetyltrimethylammonium bromide / alkyl polyglucoside surfactant mixture

Interaction of DNA with a CTAB/APG mixture was studied by determining its phase behavior. Results showed that, at low DNA concentration, the addition of APG could lead to earlier turbidity, indicating that APG can strengthen the interaction between CTAB and DNA. At high DNA concentration, however, APG had little influence on the turbidity boundary. We found that addition of salt could also lead to such an asymmetry of the phase map. Two mechanisms were presented to account for the asymmetry of the phase behavior. At the lower DNA concentration, it was assumed that the surfactant was bound to DNA in a way similar to that of micelle formation. That is, the binding is dominated by hydrophobic association processes. APG can facilitate this process by forming a surfactant mixture with CTAB, and salt facilitates this process by salting out effects. At high DNA concentrations, surfactants bind to DNA mainly through random electrostatic interaction. Addition of salt screens this interaction and therefore delays the turbidity. APG, however, exerts little influence on this process. Viscosity measurements at low DNA concentration showed that the complex with APG is more compact than that of CTAB alone with DNA.     

A comparison of some rheophysical properties of cetyltrimethylammonium bromide/H2O and cetyltrimethylammonium bromide/D2O solutions

In this paper, we report the results of rheological and optical experiments performed on two solutions of cetyltrimethylammonium bromide in D₂O and H₂O. The molar concentration of surfactant is the same in both solvents, with the solvents only differing in their atomic number. Important differences in the behaviour of the shear stress and of the birefringence intensity with the shear rate are found. We try to interpret these results by referring to the difference in solubility of ionic salts in D₂O and H₂O. Received: 25 January 1999 Accepted in revised form: 12 May 1999     

Ultrafiltration of cetyltrimethylammonium bromide solutions

Permeation data of cetyltrimethylammonium bromide (CTABr) in water by ultrafiltration (UF) through zircon membranes are reported as a first step in the knowledge of micellar enhanced ultrafiltration of heavy metals by cationic surfactants [1]. The experimental results are analysed using a model of diffusion in the membrane matrix based on the thermodynamics of irreversible processes (TIP). A comparison with the classical model of resistances in series indicates that these two approaches are consistent and that the TIP method leads to new insights into the observed resistances. The major insight relates to the understanding of the membrane resistance in terms of interactions membrane-permeants and permeants-permeants.     

Gelatin microemulsion-based gels with the cationic surfactant cetyltrimethylammonium bromide: a self-diffusion and conductivity study

In this contribution we demonstrate that gelatin can jellify also water-in-oil microemulsions based on the cationic surfactant cetyltrimethylammonium bromide (CTAB). The partial stability diagram of the system CTAB + 1-pentanol + water + hexane + gelatin was determined. The resulting microemulsion-based gels (MBGs) were characterized by means of conductivity and pulsed gradient spin-echo NMR. For the first time the water self-diffusion coefficient was measured in gelatin MBGs, and the results were successfully analyzed in terms of diffusion in an interconnected network of aqueous channels.     

Isotachophoretic separation of cetyltrimethylammonium bromide

Capillary isotachophoresis (ITP), equipped with the conductivity detection, was tested for the separation of cetyltrimethylamonium (CTMA) bromide. To prevent adsorption of CTMA to the capillary walls, several neutral polymers and ethanol were added into the leading electrolytes. Unlike polymer additives, the CTMA free monomers and micelles, created as a result of the isotachophoretic concentration effect, were recognised in the presence of ethanol from 10 to 25% (v/v). At 30% of ethanol, only a single zone of CTMA monomer was registered because the micellization process did not take place under this condition.Employing an ITP apparatus in the column-coupling configuration, the operational system with 30% of ethanol was tested for the determination of CTMA in hair conditioners. The achieved detection limits were about 0.02 mM. Both model solutions and real samples of hair conditioners were analysed with the precision about R.S.D. = 3%. One analysis in the column-coupled system takes circa 15 min.     

Influence of cetyltrimethylammonium bromide on phosphatidylcholine-coated capillaries

Large unilamellar vesicles of egg-phosphatidylcholine (eggPC), a naturally occurring phospholipid, were used in capillary electrophoresis (CE) for semi-permanent coating of fused silica capillaries. The stability of the phospholipid coating was tested at different cetyltrimethylammonium bromide (CTAB) concentrations with and without CaCl₂ present in the coating solution. The effect of physical factors influencing the coating stability (e.g. duration of the coating time, storage temperature of the coating solution) were also studied. Standing overnight in background electrolyte (BGE) solution did not alter the eggPC phospholipid coating noticeably. The performance of the coating was tested with a mixture of basic proteins (lysozyme, ribonuclease A and -chymotrypsinogen A). Highest efficiencies (over 200,000 plates m^–1) were achieved when the capillary was filled for 15 h with a liposome solution containing both CTAB and CaCl₂.Electronic Supplementary Material Supplementary material is available for this article at     

The aggregation behavior between anionic carboxymethylchitosan and cetyltrimethylammonium bromide: MesoDyn simulation and experiments

The aggregation behavior between carboxymethylchitosan (CMCHS) and cetyltrimethylammonium bromide (CTAB) is investigated by MesoDyn simulation and experimental techniques, for increasing CTAB concentrations. Mixed CMCHS/CTAB bulk aggregates are formed in the solution. Simulation results give the morphologies of aggregates clearly and illustrate the two stages for the formation of aggregates: the first stage is CTAB molecules aggregating on the CMCHS chain and the second stage is the equilibrium stage. A viscosity maximum and a hydrodynamic radius minimum at a certain CTAB concentration reveal the bridging structure of the polymer chains by the micelles. Transmission electron microscopy (TEM) images give the bridging structure clearly. At higher surfactant concentrations, light scattering and TEM show the existence of larger structures, whose size increases with CTAB concentration. According to the simulation and experimental results, the process of aggregate formation and aggregation mechanism are analyzed. Initially CMCHS and CTAB form network structure due to the bridge action of CTAB micelles, while the network structure disappears gradually and is replaced by ellipsoidal CMCHS/CTAB aggregate structure with CTAB concentration increasing.     

Role of cetyltrimethylammonium bromide (cationic surfactant) on the tryptophan–MnO4 reaction

Upon addition of permanganate to a solution of tryptophan (Trp), yellow-brown color species appears within the time of mixing of tryptophan in absence and presence of cetyltrimethylammonium bromide (CTAB), which was stable for some days. Spectroscopic and kinetic evidences suggest the formation of water-soluble colloidal MnO₂ as the most stable reduction product of MnO₄⁻. Carbon dioxide and ammonia are not formed as the oxidation products. Carbon–carbon double bond of indole moiety of Trp is responsible for the fast reduction of permanganate. Cetyltrimethylammonium bromide catalyses the permanganate oxidation of Trp with a rate enhancement of ca. 200-fold. Sub- and postmicellar catalytic effect of CTAB ascribed to the association/incorporation/solubilization of both reactants (MnO₄⁻ and Trp) with the CTAB aggregates and into the Stern layer of cationic micelles. Quantitative kinetic analysis of the rate constant–[CTAB] data has been performed on the basis of modified pseudo-phase model of the micelles. A comparison was made of the oxidation rates of different amino acids by permanganate. The order of the effectiveness was as follows: tryptophan  tyrosine  phenylalanine.     

Effect of cetyltrimethylammonium bromide on the migration of polyaromatic hydrocarbons in capillary electrokinetic chromatography

The separation of different ring numbered polyaromatic hydrocarbons (PAHs) was accomplished by using cetyltrimethylammonium bromide (CTAB) in capillary electrokinetic chromatography. In order to increase the solubilities and selectivities of PAHs, acetonitrile (ACN) was used as an organic modifier. Under the optimised conditions, 11 aromatic compounds were separated within 14.5 min in a running electrolyte containing 10 mM phosphate, 30 mM CTAB, and 40% ACN at pH 6.0. The effects of CTAB and ACN concentrations, voltage and pH on the resolution were investigated. Reproducibilities of migration times range between 0.55 and 1.27 R.S.D.% and peak areas between 1.02 and 7.23 R.S.D.%. Limit of detections (LODs) range between 0.09 and 2.24 μg ml⁻¹. This new and fast separation method of PAHs was applied to cooked oil sample.     

Control of the catalytic effect of cetyltrimethylammonium bromide micelles by the addition of background electrolyte and nonionic surfactant

The variation of the microscopic properties (surface potential, micropolarity, etc.) of the interface of cetyltrimethylammonium bromide micelles upon the addition of a background electrolyte or the nonionic surfactant Triton X-100 decreases the rates of ion-molecular reactions, namely, alkaline hydrolysis of carboxylic acid esters and tetracoordinate phosphorus acid esters, and results in the shift of acid-base equilibria. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1933–1940, October, 2007.     

Substoichiometric determination of mercury with cetyltrimethylammonium bromide

A radiometric method based on substoichiometric isotope dilution analysis has been developed for the determination of mercury using cetyltrimethylammonium bromide (CTAB) as the substoichiometric reagent. The method is based on the extraction of mercury as an ionassociation complex of tetraiodomercurate(II) ion with a substoichiometric amount of CTAB in benzene. The calibration graph was found to be linear in the range 0–10 μg Hg (II) in the aqueous phase of 10 ml volume. A detection limit of 0.06 μg·ml⁻¹ could be achieved by the proposed method. The relative standard deviation of the method was found to be 3.0% and the method has been successfully applied to study the determination of mercury in various synthetic mixtures.     

Influence of cetyltrimethylammonium bromide on physicochemical properties and microstructures of chitosan-TPP nanoparticles in aqueous solutions

The nanoparticles of chitosan (CS) were prepared using pentasodium triphosphate (TPP) as a crosslinking agent and the influences of cetyltrimethylammonium bromide (CTAB) on the physicochemical properties of the CS-TPP nanoparticles were first studied by laser light scattering, zeta potential, and transmission electron microscopy (TEM). The concentration played a significant role in controlling the particle size of CS and the overlap concentration c(*) was testified to be about 1.0 mg/mL. The combination of static light scattering (SLS) and dynamic light scattering (DLS) allowed us to obtain more information about the CS-TPP nanoparticles in the presence of surfactant molecules. The addition of CTAB could reduce the hydrodynamic diameter of nanoparticles effectively in the salt solutions and simultaneously increase the zeta potential of the nanoparticles. The effect of CTAB concentration on the size of CS-TPP nanoparticle was also examined. The critical micelle concentration (CMC) of CTAB was used to interpret the complicated complex formed by the polyelectrolyte and the surfactant. Finally, TEM was used to observe the CS-TPP nanoparticles, which were affected by CTAB, to verify the results obtained by light scattering.