T-butanol Concentration Research Articles

Improvement of biodiesel production from palm oil by co-immobilization of Thermomyces lanuginosa lipase and Candida antarctica lipase B: Optimization using response surface methodology

Candida antarctica lipase B (CALB) and Thermomyces lanuginose lipase (TLL) were co-immobilized on epoxy functionalized silica gel via an isocyanide-based multicomponent reaction. The immobilization process was carried out in water (pH 7) at 25 °C, rapidly (3 h) resulting in high immobilization yields (100%) with a loading of 10 mg enzyme/g support. The immobilized preparations were used to produce biodiesel by transesterification of palm oil. In an optimization study, response surface methodology (RSM) and central composite rotatable design (CCRD) methods were used to study the effect of five independent factors including temperature, methanol to oil ratio, t-butanol concentration and CALB:TLL ratio on the yield of biodiesel production. The optimum combinations for the reaction were CALB:TLL ratio (2.1:1), t-butanol (45 wt%), temperature (47 °C), methanol: oil ratio (2.3). This resulted in a FAME yield of 94%, very close to the predicted value of 98%.

Use of Aqueous Two-Phase and Three-Phase Partitioning Systems for Purification of Lipase Obtained in Solid-State Fermentation by Rhizopus arrhizus

Background: Purification of enzymes by conventional methods such as precipitation and chromatographic techniques is a costly and time-consuming procedure and may lead to low yields of enzyme activity. Alternative liquid-liquid extraction methods such as Aqueous Two-Phase Systems (ATPS) and Three Phase Partitioning (TPP) are characterized by the high enzyme yields and purification degree. Objective: The objective of this study was the application of partitioning systems ATPS and TPP for purification of lipase produced in solid-state fermentation by Rhizopus arrhizus. Methods: ATPS and TPP were used for purification of lipase, obtained by solid state cultivation of Rhizopus arrhizus. Results: Lipase was isolated with PEG4000/potassium sodium tartrate ATPS and the effect of the system composition, including PEG 4000 and potassium sodium tartrate concentrations on lipase partitioning was studied. When using 30% PEG4000/21% potassium sodium tartrate, lipase was distributed in the top phase, and the highest recovery yield of 217% and purification fold of 6.1 were achieved. It was found that at PEG4000 concentration of or higher than 15%, the enzyme was present in the top polymer-rich phase with a partitioning yield of over 90%. Upon application of TPP for lipase isolation, the effect of t-butanol concentration, ammonium sulfate concentration and pH on enzyme partitioning was investigated. The highest lipase recovery yield of 71% and 19.1-fold purification were achieved in the interfacial phase in the presence of 30% ammonium sulfate saturation with 1.0:0.5 crude extract/t-butanol ratio at pH 7 in a single step. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis and zymographic analysis showed significant purification of lipase by TPP and the presence of two multiple forms of the enzyme. Conclusion: ATPS (PEG4000/ Potassium sodium tartrate) and TPP (1.0:0.5 crude extract/t-butanol ratio, 30% ammonium sulfate saturation, pH 7) proved to be rapid methods for the isolation and purification of lipase and they can be used in downstream processing for industrial preparation of the enzyme.

Co-immobilization of Rhizomucor miehei lipase and Candida antarctica lipase B and optimization of biocatalytic biodiesel production from palm oil using response surface methodology

Lipases from Candida antarctica B (nonspecific lipase) and Rhizomucor miehei (1,3-specific lipase) were simultaneously immobilized on epoxy functionalized silica gel under mild conditions. The results showed rapid and simple immobilization of 4–15 mg of CALB:RML (different ratios 4:1, 2:1, 1.5:1, 1:1) on 1 g of support after 6 h. The thermal stability of derivatives and also their stability in methanol were greatly improved compared to the single immobilized enzyme. All the derivatives were also used to catalyze the transesterification of palm oil with methanol to produce fatty acid methyl esters (FAMEs). Response surface methodology (RSM) and a central composite rotatable design (CCRD) was used to study the effects of five factors, reaction temperature, methanol/oil ratio, reaction time, t-butanol concentration and CALB:RML ratio on the fatty acid methyl esters (FAME) yield. A quadratic polynomial equation was obtained for methanolysis reaction by multiple regression analysis. The optimum combinations for the reaction were CALB:RML ratio (2.5:1), t-butanol to oil (39.9 wt%), temperature (35.6 °C), methanol:oil ratio (5.9), reaction time 33.5 h. FAME yield of 78.3.5%, which was very close to the predicted value of 75.2%, was obtained. Verification experiment confirmed the validity of the predicted model.

Extraction of Oil from Flaxseed (Linum usitatissimum L.) Using Enzyme-Assisted Three-Phase Partitioning.

In this study, enzyme-assisted three-phase partitioning (EATPP) was used to extract oil from flaxseed. The whole procedure is composed of two parts: the enzymolysis procedure in which the flaxseed was hydrolyzed using an enzyme solution (the influencing parameters such as the type and concentration of enzyme, temperature, and pH were optimized) and three-phase partitioning (TPP), which was conducted by adding salt and t-butanol to the crude flaxseed slurry, resulting in the extraction of flaxseed oil into alcohol-rich upper phase. The concentration of t-butanol, concentration of salt, and the temperature were optimized to maximize the extraction yield. Under optimized conditions of a 49.29% t-butanol concentration, 30.43% ammonium sulfate concentration, and 35°C extraction temperature, a maximum extraction yield of 71.68% was obtained. This simple and effective EATPP can be used to achieve high extraction yields and oil quality, and thus, it is potential for large-scale oil production.

Ozonation of p-nitrophenol at different pH values of water and the influence of radicals at acidic conditions

Ozonation of p-nitrophenol solution was carried out without pH control and at constant pH values of 2, 7 and 10. The effect of radical scavenger t-butanol at pH 2 was studied for t-butanol concentrations of 0.0, 0.000225, 0.00225 and 0.0225mol/dm3. The ozone decomposition rate was computed for each pH as a function of time on the basis of each experimental run. The consumed ozone dose was calculated at each pH and at each t-butanol concentration at pH 2. The results indicate that pH determines the relative production rates of the first intermediates, hydroquinone and 4-nitrocathecol, on the reaction path of p-nitrophenol decomposition and that radicals play an important role in ozonation at low pH. The results also indicate that there exists some optimum t-butanol concentration at which slowest 4-nitrocathecol production occurs, and further, there exists some optimum t-butanol concentration for highest consumed ozone dose per amount of decomposed p-nitrophenol at pH 2.

Advanced oxidation removal of NO and SO2 from flue gas by using ultraviolet/H2O2/NaOH process

In this article, the effects of several process parameters (energy density per unit solution, H2O2 concentration, NaOH concentration, gas flow, solution temperature, NO concentration, O2 concentration, SO2 concentration, Fe2+ concentration and t-butanol concentration) on removal of NO from flue gas by UV (Ultraviolet)/H2O2 advanced oxidation combining with NaOH absorption (UV/H2O2/NaOH process) were investigated in a photochemical reactor. The results indicate that under all experimental conditions, SO2 can be removed completely. Increasing H2O2 concentration, NaOH concentration, energy density per unit solution, t-butanol concentration and low concentration of Fe2+ have a significant role in promoting removal of NO. NO removal efficiency sharply reduces with the increase of gas flow, NO concentration and high concentration of Fe2+. NO removal is slightly inhibited by increasing solution temperature and SO2 concentration, but is slightly enhanced by increasing O2 concentration. Oxidation of NO by OH free radicals plays an important role in the removal of NO by UV/H2O2/NaOH process. NO3− is the final reaction product of NO removal by UV/H2O2/NaOH process. The reaction mechanism of NO removal by UV/H2O2/NaOH process has also been proposed.

Thermodynamic properties of ternary mixtures containing water, 2-ethoxyethanol, and t-butanol at 298.15 K

Ultrasonic speeds and isentropic compressibilities were measured at 298.15 K in the water-rich region of aqueous solutions of water + 2-ethoxyethanol (2EE) + t-butanol. The excess properties of ultrasonic speed and isentropic compressibility were also calculated and have been discussed in terms of molecular interactions. The concentrations of t-butanol at which ultrasonic speed becomes maximum and isentropic compressibility becomes minimum are found to decrease with increase in the concentration of 2EE in the cosolvent (aqueous 2EE). This behavior indicates that the aqueous ternary solutions are less structured than aqueous t-butanol. This behavior is explained as due to a decrease in the ability of t-butanol to form clathrate hydrates owing to the presence of 2EE. When the concentration of 2EE in the cosolvent (x2EE) > 0.14, ultrasonic speed decreases and isentropic compressibility increases with concentration of t-butanol indicating that the ternary solution behaves as normal solution wherein any further addition of 2EE or t-butanol leads to destabilization of the hydrogen bonded structure of water and t-butanol looses its ability to form clathrate hydrates in aqueous solutions.

Ultrasonic Investigations in Ternary Mixtures Containing Water, 2-Butoxyethanol and t-Butanol at 298.15 K

Ultrasonic speeds in, and isentropic compressibilities of, aqueous solutions of water + 2-butoxyethanol (2BE)+t-butanol have been determined at 298.15 K. The concentrations of t-butanol at which the ultrasonic speed becomes maximum and isentropic compressibility becomes minimum are found to decrease with increases in the concentration of 2BE, x2BE, in the cosolvent (aqueous 2BE). This behavior indicates that the aqueous ternary solutions are less structured than aqueous t-butanol. In the presence of 2-butoxyethanol, enhancement in the hydrogen bonded structure of water due to hydrophobic hydration between t-butanol and water molecules decreases as the concentration of x2BE in the cosolvent increases. When x2BE>0.2, the ternary solution behaves like a normal liquid. This behavior is also very well reflected in the concentration dependence of the excess ultrasonic speed and excess isentropic compressibility. The optimum concentrations of t-butanol, (\(x_{\mathrm{t}\mbox{-}\mathrm{B}}\))opt, at which extrema in ultrasonic speed, isentropic compressibility, excess ultrasonic speed and excess isentropic compressibility are observed decrease with increase in x2BE in the cosolvent. The results are explained as being due to a reduction in the strength of hydrophobic interactions responsible for enhancement in the structure of water in aqueous t-butanol in the presence 2BE. Beyond (\(x_{\mathrm{t}\mbox{-}\mathrm{B}}\))opt, the hydrogen bonded network of water collapses and water, 2-butoxyethanol and t-butanol molecules interact with each other as normal liquid molecules.

Different Molten Globule-like Folding Intermediates of Hen Egg White Lysozyme Induced by High pH and Tertiary Butanol

We have provided evidence that hen egg white lysozyme (HEWL) existed in alpha helical and beta structure dominated molten globule (MG) states at high pH and in the presence of tertiary butanol, respectively. Circular dichroism (CD), intrinsic fluorescence, ANS binding and acrylamide-induced fluorescence quenching techniques have been used to investigate alkali-induced unfolding of HEWL and the effect of tertiary butanol on the alkaline-induced state. At pH 12.75, HEWL existed as molten globule like intermediate. The observed MG-like intermediate was characterized by (i) retention of 77% of the native secondary structure, (ii) enhanced binding of ANS (approximately 5 times) compared to native and completely unfolded state, (iii) loss of the tertiary structure as indicated by the tertiary structural probes (near-UV, CD and Intrinsic fluorescence) and (iv) acrylamide quenching studies showed that MG state has compactness intermediate between native and completely unfolded states. Moreover, structural properties of the protein at isoelectric point (pI) and denatured states have also been described. We have also shown that in the presence of 45% tertiary butanol (t-butanol), HEWL at pH 7.0 and 11.0 (pI 11.0) existed in helical structure without much affecting tertiary structure. Interestingly, MG state of HEWL at pH 12.7 transformed into another MG state (MG2) at 20% t-butanol (v/v), in which secondary structure is mainly beta sheets. On further increasing the t-butanol concentration alpha helix was found to reform. We have proposed that formation of both alpha helical and beta sheet dominated intermediate may be possible in the folding pathway of alpha + beta protein.

Ultrasonic behaviour of ternary mixtures containing water, dimethylformamide and t-butanol at 298.15 K

Ultrasonic velocities in and adiabatic compressibilities of aqueous solutions of a water+dimethylformamide (DMF)+t-butanol have been determined at 298.15 K. The concentrations of t-butanol at which ultrasonic velocity becomes maximum and adiabatic compressibility becomes minimum are found to decrease with increase in the concentration of DMF in the cosolvent (aqueous DMF). This behaviour indicates that the aqueous ternary solutions are less structured than aqueous t-butanol. This behaviour is also well reflected in the concentration dependence of excess ultrasonic velocity and excess adiabatic compressibility. It is due to a decrease in the ability of t-butanol to form clathrate hydrates owing to the presence of DMF. When the concentration of DMF in the cosolvent ( X DMF)>0.2, ultrasonic velocity decreases and adiabatic compressibility increases with the concentration of t-butanol indicating that the ternary solution behaves as a normal solution where in any further addition of DMF or t-butanol leads to destabilization of the hydrogen bonded structure of water and t-butanol looses its ability to form clathrate hydrates in aqueous solutions.

Formation of Bromate Ion Through a Radical Pathway in a Continuous Flow Reactor

ABSTRACT The contribution of ozone and hydroxyl radical to the formation of bromate ion was investigated in a continuous flow reactor. Experiments were conducted under a wide range of ozone dose (0.7 ∼ 3.8 mgL), pH (6.5 ∼ 8.5), and t-butanol concentration (0 ∼ 0.5 mM). The formation of bromate ion was found to depend on radical reaction pathway, because the amount of bromate ion formed increased with pH and decreased with t-butanol, a radical scavenger, even when dissolved ozone concentrations were almost the same. In fact, the amount of bromate ion formed was reduced by 90% in the presence of t-butanol. Furthermore, the formation of bromate ion occurred even when dissolved ozone was not significantly detected in the presence of organic matter (TOC of 1 mgCL). The second-order reaction rate constant of hydroxyl radical with bromide ion, k HO,Br− of 1.7 × 109 (M−1s−1), was obtained on the assumption that the reactions of bromide ion and t-butanol with hydroxyl radical were competitive with each other in the presence of t-butanol and that the formation of bromate ion depended on the reaction of bromide ion with hydroxyl radical. Therefore, it is concluded that the reaction of bromide ion with hydroxyl radical dominated in the overall reaction from bromide ion to bromate ion in the continuous flow reactor.

Effects of alcohol mobile-phase modifiers on the structure and chiral selectivity of amylose tris(3,5-dimethylphenylcarbamate) chiral stationary phase

Following a previous publication, the present paper reports additional results on the effects of alcohol mobile-phase modifiers on the structure and chiral selectivity of amylose tris(3,5-dimethylphenylcarbamate) (Chiralpak AD) chiral stationary phase (CSP). Solid-state NMR ( 1 H/ 13 C CPMAS) was utilized to identify and compare structural differences in Chiralpak AD caused by the various alcohol mobile-phase modifiers, many of which were not studied in the previous publication. The influences of the various alcohol modifiers (in hexane-based mobile phase) on the structure and chiral selectivity of the CSP were studied and compared. CPMAS spectra of Chiralpak AD flushed with the mobile phases displayed clear evidence of solvent incorporation into the CSP. When alcohol modifiers with varying size and bulkiness were used in the mobile phase, differences in structure and chiral selectivity were observed on Chiralpak AD based on solid-state NMR and chromatographic data. The change of t-butanol concentration in the t-butanol/hexane mobile phase caused changes of structure and chiral selectivity of the Chiralpak AD. These data further support our belief that the different chiral selectivities of the CSP associated with the use of different alcohol modifiers are due to different alterations of the steric environment of the chiral cavities in the CSP by the different mobile-phase modifiers.

Electrocatalytic oxidation of benzyl alcohol in alkaline medium on RuO2-coated titanium electrode

The heterogeneous electrocatalytic redox behaviour of RuO2 electrodes fabricated by thermal decomposition is investigated with and without benzyl alcohol using cyclic voltammetric and potentiodynamic techniques. The cyclic voltammetric results show that benzyl alcohol oxidation is mediated by perruthenate ion electrogenerated at the electrode surface. Evaluation of kinetic parameters in relation to Tafel lines allows the postulation of a plausible reaction scheme in which benzyl alcohol adsorbs on the RuO2 electrode surface and the rate determining step is chemical reaction between perruthenate and adsorbed species. The reaction orders with respect to benzyl alcohol and OH− concentrations are 0.85 and 1, respectively. The results in galvanostatic electrolysis show that the major product for benzyl alcohol oxidation in an aqueous solution is benzaldehyde, and the organic yield is affected by such electrolysis conditions as t-butanol concentration, electrolysis current density, KOH concentration and electrolysis temperature.

Sulfhydryl Protection and the Oxygen Effect on Radiation-Induced Inactivation of r-Chromatin in Vitro: Influence of an OH Scavenger: t-Butanol

Transcriptionally active r-chromatin from Tetrahymena has been irradiated in dilute phosphate buffer, pH 7.2, in the presence of the sulfhydryl compound 2-mercaptoethanol [MSH]. MSH was more protective against radiation-induced inactivation of transcription under N2 than under O2. The OH scavenger, t-butanol, on the other hand, gives significantly less protection under N2 than under O2, apparently due to inactivation by secondary t-butanol radicals under anoxia as shown previously (C. Herskind and O. Westergaard, Radiat. Res., 114, 28-41 (1988). However, MSH was found to restore most of the protective effect of t-butanol under N2. Inactivation was studied as a function of MSH concentration [0.03-10 mM] at different, fixed concentrations of t-butanol [3-300 mM]. The observed protection may be explained essentially in terms of (1) OH scavenging, (2) "repair" of DNA radicals by H-atom transfer from MSH under N2 in competition with fixation of damage under O2, and (3) protection against inactivation by secondary t-butanol radicals by H-atom transfer to these radicals. The sensitizing effect of oxygen in the presence of MSH is reduced by t-butanol and may even be reversed to produce an apparently protective effect. This finding is discussed in terms of residual inactivation by secondary radicals. The significance of OH scavengers as potential modifiers of oxygen enhancement ratio values is discussed.

Gamma-radiolysis of poly(A) in aqueous solution: efficiency of strand break formation by primary water radicals.

gamma-Radiation-induced single-strand break formation (ssb) in polyadenylic acid (poly(A] has been determined in Ar and N2O-saturated aqueous solution in the presence of different concentrations of t-butanol. Strand breaks were monitored by a low-angle laser light-scattering technique. The efficiencies for strand breakage caused by solvated electrons, hydrogen atoms and OH radicals have been found to be 0.25, 0.20 and 7.8 per cent, respectively. The efficiency of OH radicals depends only slightly on pH (pH 5.0, 7.5 and 9.0) and is independent of the presence of salt (0.01 mol dm-3 NaC1O4) and of the irradiation temperature (20 degrees C and 70 degrees C). The efficiency of OH for ssb formation obtained in this work with poly(A) is much smaller than that of poly(dA). This is explained by the different molecular conformations of the sugar moiety of poly(A) (3'-endo) and poly(dA) (2'-endo). With increasing t-butanol concentration more strand breaks are formed than expected from simple homogeneous competition kinetics of poly(A) and t-butanol for OH radicals. This result is considered to be due to nonhomogeneous reaction kinetics in the above-mentioned competition. The rate constants for the reaction of OH and H with poly(A) have been determined.

Kinetics of the solvolysis of the cis-chloroazidobis-(1,2-diaminoethane)cobalt(III) ion in water+t-butanol mixtures

Rate constants for the solvolysis of the complex ioncis-[Coen2N3Cl]+ have been determined for a range of temperatures in mixtures of water witht-butanol ranging up to 50% v/v of the latter. Linear plots of log (rate constant) against the reciprocal of the absolute temperature are obtained at all concentrations oft-butanol and the variations of the enthalpy and entropy of activation with solvent composition show extrema at compositions where extrema occur in the physical properties of the mixture which are influenced by solvent structure. The importance of solvent structure is shown by the curved plot found for log (rate constant) against reciprocal of dielectric constant at constant temperature. The application of a free energy cycle to the free energies of activation in water and in the mixture and the free energies of transfer of individual ionic species between water and the mixtures shows that the effect of changes in solvent structure on the reacting cation in the transition state dominates over that in the initial state.

Reaction rate of OH radicals with phi X174 DNA: influence of salt and scavenger.

A derivation is given for the dependence of the rate constant of the reaction of OH radicals with a spherical macromolecule on the rate by which such radicals are scavenged by the medium. Experiments were carried out with oxygenated solutions of dilute single-stranded phi X174 DNA at 10(-4)M NaCl (large reaction radius of DNA) or at 10(-4)M NaCl + MgCl2 (small reaction radius) with t-butanol as a scavenger. The results of these experiments cannot be described by simple second-order competition, but can be explained by the predicted dependence of the rate constant of the reaction OH + DNA on the concentration of t-butanol. Furthermore, the results show that only part of the reactions of OH radicals with phi X174 DNA leads to DNA inactivation, and that even at zero scavenger concentration OH radicals are scavenged by other molecules than DNA, presumably impurities remaining even after careful purification of the DNA.

Effects of t-butanol on micelle formation by a series of long chain alkyltrimethylamonnium bromides

Micelles of decyl-, dodecyl-, and hexadecyltrimethylammonium bromide (C 10TAB, C 12TAB, C 16TAB) were studied at 298°K in 0.5 mole dm −3 sodium bromide and in the presence of various concentrations of t-butanol. (1) A fluorescent probe, N-phenylnaphthylamine, was used to estimate critical micelle concentrations (CMC) and the polarity of the hydrocarbon core of the micelles. (2) The ultraviolet absorption spectrum of solubilized benzene was used to estimate the polarity of the headgroup region. (3) Viscosity measurements were used to derive information about micelle shapes and solvent penetration. (4) Low-angle laser light scattering was used to determine aggregation numbers. Added t-butanol lowers the CMC of C 10TAB but increases that of C 16TAB. When mole fraction of t-butanol reaches 0.03 the micelles have a looser structure with greaer solvent penetration than the classical detergent micelle. Micelles are not formed when the mole fraction of t-butanol exceeds 0.03. t-Butanol penetrates the hydrocarbon core of the micelles and is adsorbed at the head group region. The optimum surface area per head group is consequently increased with the result that the micelles are smaller in the presence of t-butanol than in water alone and they are spherical rather than ellipsoidal.

Development of physical dependence on t-butanol in rats: An examination using schedule-induced drinking

Rats were exposed to various concentrations of t-butanol as their only available fluid in either the home cage or a schedule-induced drinking situation previously shown to induce overdrinking of ethanol. When animals consumed at least 3 g/kg/day of t-butanol for 90 days, independent of the condition, withdrawal symptoms were observed. This daily intake occurred only when the concentration of t-butanol was 3% (v/v) or greater. The schedule-induction procedure did not induce t-butanol overdrinking at any concentration tested as it does with ethanol, but its use did result in increased probability of the occurrence of withdrawal symptoms over the home cage condition. In no cases was the severity of withdrawal from t-butanol as great as previously reported for ethanol. When the concentration of t-butanol was increased to 3.5% (v/v), severe toxic reactions were found, that included anorexia, self-mutilation, and deaths from no specific determinable causes.

ChemInform Abstract: HYDROPHOBIC INTERACTION IN AQUEOUS ORGANIC MIXED SOLVENTS

The standard free energy of hydrophobic interaction between alkyl chains has been measured in aqueous solutions of t-butanol, dioxan, dimethyl sulphoxide and dimethyl formamide.The results make it clear that hydrophobic interaction (in the sense of a pair-wise interaction between hydrophobic groups otherwise surrounded by water) is not simply a partial reversal of solution of the non-polar molecules in water. Hydrophobic interaction should therefore be distinguished from phenomena, such as the formation of detergent micelles or phospholipid bilayers, in which non-polar molecules are completely removed from water. Only in the latter case is “reversal of solution” a correct description.The experimental method was measurement of conductance of long chain alkyltrimethylammonium carboxylate solutions. Ion pair association constants, and hence free energies of ion pair formation were calculated from these data. Then by systematically varying the alkyl chain length it was possible to separate the free energy of hydrophobic interaction from the electrostatic interaction between the charged groups.Moderate concentrations of t-butanol, dimethyl sulphoxide and dimethyl formamide strengthened hydrophobic interactions. All concentrations of dioxan weakened hydrophobic interactions. Maximum hydrophobic interaction occurred with those solute concentrations which maximised the three dimensional hydrogen bonded structure of water.The results explain some of the odd effects of alcohols and other structure making solutes on the stability of proteins.