Hydrogen peroxide biosensor based on a myoglobin/hydrophilic room temperature ionic liquid film

The composite film based on Nafion and hydrophilic room temperature ionic liquid (RTIL) 1-butyl-3-methyl-imidazolium chloride ([bmim]Cl) was used as an immobilization matrix to entrap myoglobin (Mb). The study of ionic liquid (IL)-Mb interaction by ultraviolet-visible (UV-vis) spectroscopy showed that Mb retains its native conformation in the presence of IL. The immobilized Mb displayed a pair of well-defined cyclic voltammetric peaks with a formal potential (E_o^’) of −0.35 V in a 0.1 M phosphate buffer solution (PBS) of pH 7.0. The immobilized Mb exhibited excellent electrocatalytic response to the reduction of hydrogen peroxide, based on which a mediator-free amperometric biosensor for hydrogen peroxide was designed. The linear range for the determination of hydrogen peroxide was from 1.0 to 180 μM with a detection limit of 0.14 μM at a signal/noise ratio of 3. The apparent Michaelis constant () for the electrocatalytic reaction was 22.6 μM. The stability, repeatability, and selectivity of the sensor were evaluated. The proposed biosensor has a lower detection limit than many other IL-heme protein-based biosensors and is free from common interference in hydrogen peroxide biosensors.     

Improving enzymatic hydrolysis of wheat straw using ionic liquid 1-ethyl-3-methyl imidazolium diethyl phosphate pretreatment

This study aims to establish a cellulose pretreatment process using ionic liquids (ILs) for efficient enzymatic hydrolysis. The IL 1-ethyl-3-methyl imidazolium diethyl phosphate ([EMIM]DEP) was selected in view of its low viscous and the potential of accelerating enzymatic hydrolysis, and it could be recyclable. The yield of reducing sugars from wheat straw pretreated with this IL at 130 °C for 30 min reached 54.8% after being enzymatically hydrolyzed for 12 h. Wheat straw regenerated were hydrolyzed more easily than that treated with water. The fermentability of the hydrolyzates, obtained after enzymatic saccharification of the regenerated wheat straw, was evaluated using Saccharomyces cerevisiae. This microbe could ferment glucose efficiently, and the ethanol production was 0.43 g/g glucose within 26 h. In conclusion, the IL [EMIM]DEP shows promise as pretreatment solvent for wheat straw, although its cost should be reduced and in-depth exploration of this subject is needed.     

NMR evidence for the participation of triflated ionic liquids in glycosylation reaction mechanisms

A systematic low-temperature NMR study of a glycosylation reaction was performed in the presence of different ionic liquids and acidic catalysts. The influence of the triflate anion derived from [emim][OTf] on the stereochemistry of the glycosylation products was evaluated.     

Scope and limitations of imidazolium-based ionic liquids as room temperature glycosylation promoters

The scope and limitations of imidazolium-based ionic liquids as room temperature glycosylation promoters have been studied. Herein, we report the effects of modifying the structure of the imidazolium cation and how important the choice of counter ion becomes on model glycosylation reactions of thioglycosides at room temperature in the presence of N-iodosuccinimide (NIS).     

Enhanced enzyme-catalyzed synthesis of l-methionine with ionic liquid additives

The low solubility of l-methionine and low activity of enzyme are the major hurdles during l-methionine production by the enzymatic conversion approach. In this study, we investigated various ionic liquids (ILs) as additives for the enzyme-catalyzed production of l-methionine from O-acetyl L-homoserine and methyl mercaptan. Among the ILs evaluated, we found that tetraalkylammonium hydroxide ILs enhanced the solubility of l-methionine as well as the activity of the enzyme. Methionine solubility decreased with increasing alkyl chain length but increased with increasing IL concentration. l-methionine could be dissolved up to 232 g/L in 10% tetramethylammonium hydroxide solution. The enzyme O-acetylhomoserine aminocarboxypropyltransferase reached its maximum activity when the IL concentration was 2.5% (3 times higher than that without ILs) and significantly decreased with increasing IL concentration. The stability of the enzyme also decreased rapidly after 2 h of incubation regardless of the presence or absence of ILs. Nevertheless, 74 g/L of l-methionine could be produced in a reaction media containing 2.5% tetraethylammonium hydroxide compared to 35 g/L of l-methionine obtained in a reaction system without ILs.     

Natural wool/cellulose acetate blends regenerated from the ionic liquid 1-butyl-3-methylimidazolium chloride

Dissolution and blending one of the most commonly used natural polymers, i.e., wool using a green solvent ionic liquid is described. The cleaned natural wool from merino sheep was directly dissolved and regenerated from 1-butyl-3-methylimidazolium chloride (BMIMCl) without any modifications. BMIMCl was subsequently used to develop wool/cellulose acetate (CA) blends. Blending modification of wool in this IL green solvent led to significant increase in glass transition temperature (T_g) and thermal stability compared to the pure components. It was found that there exist strong intermolecular hydrogen bonding interactions between regenerated wool and CA. Moreover homogeneous surface morphology was observed in the blends with higher CA concentrations. At the final stage of the blending process, the IL solvent was recycled completely. This work presents a green processing route for development of novel natural wool blended materials.     

Probing anion-cellulose interactions in imidazolium-based room temperature ionic liquids: a density functional study

The interactions of the cellulose molecule with several anions, including acetate , alkyl phosphate, tetrafluoroborate and hexafluorophosphate anions which are most commonly involved in the imidazolium ionic liquids (ILs), have been studied by performing density functional theory calculations. Based on calculated geometries, energies, IR characteristics, and electronic properties of the cellulose-anion complexes, it is found that the strength of interactions of anions with cellulose follows the order: acetate anion > alkyl phosphate anion > tetrafluoroborate anion > hexafluorophosphate anion, which is consistent with the experimentally observed solubility trend of cellulose in the corresponding imidazolium-based ILs. The present study may provide basic aids to some extent for understanding the dissolution behavior of cellulose in the imidazolium-based ILs.     

Synthesis of room temperature ionic liquids from carboxymethylated chitosan

Natural oligosaccharide-derived room temperature ionic liquids (RTILs) were prepared from 1-ethyl-3-methylimidazolium hydroxide (EMIM·OH) and carboxymethylated chitosan (CM-chitosan) by acid–base neutralization reaction. These EMIM·CM-chitosan ionic liquids exhibited good ionic conductivity and thermal stability, as well as low glass transition temperature, implying their potential wide applications in direct electrochemistry, biosensors, and biocatalysis.     

A room temperature ionic liquid as convenient solvent for the oxidative folding of conopeptides

We report the first example of conopeptide oxidation performed in a biocompatible ionic liquid, 1‐ethyl‐3‐methylimidazolium acetate ([C₂mim][OAc]), which enables the efficient formation of both hydrophilic and poorly water‐soluble conotoxins compared with conventional methods. Moreover, the method features a high‐concentration approach ultimately leading to higher yields at reduced separation effort. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd.     

Reversible swelling of the cell wall of poplar biomass by ionic liquid at room temperature

Time-resolved autofluorescence, Raman microspectroscopy, and scanning microprobe X-ray diffraction were combined in order to characterize lignocellulosic biomass from poplar trees and how it changes during treatment with the ionic liquid 1-n-ethyl-3-methylimidazolium acetate (EMIMAC) at room temperature. The EMIMAC penetrates the cell wall from the lumen, swelling the cell wall by about a factor of two towards the empty lumen. However, the middle lamella remains unchanged, preventing the cell wall from swelling outwards. During this swelling, most of the cellulose microfibrils are solubilized but chain migration is restricted and a small percentage of microfibrils persist. When the EMIMAC is expelled, the cellulose recrystallizes as microfibrils of cellulose I. There is little change in the relative chemical composition of the cell wall after treatment. The action of EMIMAC on the poplar cell wall at room temperature would therefore appear to be a reversible swelling and a reversible decrystallization of the cell wall.     

Quantitative determination of cellulose dissolved in 1-ethyl-3-methylimidazolium acetate using partial least squares regression on FTIR spectra

Rapid and quantitative measurements of cellulose concentrations in ionic liquids (ILs) are difficult. In this study, FTIR operated in attenuated total reflectance (ATR) mode was investigated as a tool to measure cellulose concentration in 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) and the spectra were subjected to partial least squares (PLS) regression for the quantitative determination of cellulose content. Additionally, the spectra were subjected to 7 data preprocessing methods to reduce physical effects in the spectra. Peak normalization was found to be the technique that most improved the prediction of dissolved cellulose in [emim][OAc]. When peak normalization was used for data preprocessing, a model for the quantitative estimation of cellulose content between 0 wt.% and 4 wt.% with an error of 0.53 wt.% was generated. The methods described here provide the basis for a rapid and facile technique for the determination of dissolved cellulose content in [emim][OAc].     

Hydrogen bonding of flavoprotein: II. Effect of hydrogen bonding at hetero atoms of reduced flavin on its reactivity

The effect of hydrogen bonding at hetero atoms of reduced flavin on its reactivity was studied by ab initio molecular orbital calculations. Among the atoms in the isoalloxazine nucleus of lumiflavin, C(4a) was found to be the most reactive with neutral electrophiles such as molecular oxygen, whereas no reactivity of N(5) can be expected, because of its negative charge. The reactivity of C(4a) is markedly enhanced by hydrogen bonding at N(1) and N(3) in a hydrophobic environment, while it is decreased when hydrogen bonding occurs at all the hetero atoms, as in the case of an aqueous solution of flavin.     

Microwave-assisted conversion of lignocellulosic biomass into furans in ionic liquid

Production of 5-hydroxymethylfurfural (HMF) and furfural from lignocellulosic biomass was studied in ionic liquid in the presence of CrCl₃ under microwave irradiation. Corn stalk, rice straw and pine wood treated under typical reaction conditions produced HMF and furfural in yields of 45–52% and 23–31%, respectively, within 3 min. This method should be valuable to facilitate energy-efficient and cost-effective conversion of biomass into biofuels and platform chemicals.     

Synthesis of soluble coordination polymer nanoparticles using room-temperature ionic liquid

We report a new family of soluble cyano-bridged coordination polymer nanoparticles M₃[Cr(CN)₆]₂/[BMIM][BF₄] (where M²⁺ = Ni, Mn, V^IVO; BMIM = 1-butyl-3-methylimidazolium). These nanoparticles of ca. 6 nm were synthesised in the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, which acts both as a stabilizing agent and a solvent. The magnetic properties of frozen colloids containing the nanoparticles show that the relaxation of magnetisation is strongly influenced by interparticle interactions leading to the appearance of spin-glass-like dynamics in these systems.     

Dissolution of [RhCl(PPh3)3] in the ionic liquid, 1-ethyl-3-methyl imidazolium chloroaluminate(III), and its reaction with H2. The stabilization of Rh(I) species in an ionic liquid

The solution of [RhCl(PPh₃)₃] in acidic 1-ethyl-3-methylimidazolium chloroaluminate(III) ionic liquid (AlCl₃ molar fraction, x_AlCl3=0.67) was investigated by ¹H and ³¹P{¹H} NMR. One triphenyl phosphine is lost from the complex and is protonated in the acidic media, and cis-[Rh(PPh₃)₂ClX], (2), where X is probably [AlCl₄]⁻, is formed. On, standing, 2 is converted to trans-[Rh(H)(PPh₃)₂X], (3). The reaction of 2 and H₂ also produces trans-[Rh(H)(PPh₃)₂X], (3). ¹H and ³¹P{¹H} NMR support the suggestion that a weak ligand such as [AlCl₄]⁻, present in solution may interact with the metal centre. When [RhCl(PPh₃)₃] is dissolved in CH₂Cl₂/AlCl₃/HCl for comparison, two exchanging isomers of what is probably [RhH{(μ-Cl)₂AlCl₂}{(μ-Cl)AlCl₃}(PPh₃)₂], (6) and (7), are formed.     

Weak gel of chitin with ionic liquid, 1-allyl-3-methylimidazolium bromide

This paper reports the formation of weak gel of chitin with an ionic liquid, 1-allyl-3-methylimidazolium bromide (IL). When a mixture of 5% (w/w) chitin with IL was heated at 100 °C for 48 h, the clear liquid was obtained. The experimental process was observed by the CCD camera view and the SEM analysis. From a mixture of chitin with IL in the higher concentration (7%, w/w), a more viscous material, i.e., a gel-like material was obtained. The rheological evaluations showed that both 5% (w/w) and 7% (w/w) chitins with IL behaved as weak gels.     

Biosensor based on the biocatalysis of microperoxidase-11 in nanocomposite material of multiwalled carbon nanotubes/room temperature ionic liquid for amperometric determination of hydrogen peroxide

A novel nanocomposite material of multiwalled carbon nanotubes (MWCNTs) and room temperature ionic liquid (RTIL) N-butylpyridinium hexafluorophosphate (BPPF₆) was explored and used to construct a novel microperoxidase-11 (MP-11) biosensor for the determination of hydrogen peroxide (H₂O₂). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to characterize the performance of the biosensor. Under the optimized experimental conditions, H₂O₂ could be detected in a linear calibration range of 0.5 to 7.0 × 10⁻⁷ mol L⁻¹ with a correlation coefficient of 0.9949 (n = 9) and a detection limit of 3.8 × 10⁻⁹ mol L⁻¹ at 3σ. The modified electrodes displayed excellent electrochemical response, high sensitivity, long-term stability, and good bioactivity and selectivity.     

Facile pretreatment of lignocellulosic biomass at high loadings in room temperature ionic liquids

Ionic liquids (ILs) have emerged as attractive solvents for lignocellulosic biomass pretreatment in the production of biofuels and chemical feedstocks. However, the high cost of ILs is a key deterrent to their practical application. Here, we show that acetate based ILs are effective in dramatically reducing the recalcitrance of corn stover toward enzymatic polysaccharide hydrolysis even at loadings of biomass as high as 50% by weight. Under these conditions, the IL serves more as a pretreatment additive rather than a true solvent. Pretreatment of corn stover with 1‐ethyl‐3‐methylimidizolium acetate ([Emim] [OAc]) at 125 ± 5°C for 1 h resulted in a dramatic reduction of cellulose crystallinity (up to 52%) and extraction of lignin (up to 44%). Enzymatic hydrolysis of the IL‐treated biomass was performed with a common commercial cellulase/xylanase from Trichoderma reesei and a commercial β‐glucosidase, and resulted in fermentable sugar yields of ～80% for glucose and ～50% for xylose at corn stover loadings up to 33% (w/w) and 55% and 34% for glucose and xylose, respectively, at 50% (w/w) biomass loading. Similar results were observed for the IL‐facilitated pretreatment of switchgrass, poplar, and the highly recalcitrant hardwood, maple. At 4.8% (w/w) corn stover, [Emim][OAc] can be readily reused up to 10 times without removal of extracted components, such as lignin, with no effect on subsequent fermentable sugar yields. A significant reduction in the amount of IL combined with facile recycling has the potential to enable ILs to be used in large‐scale biomass pretreatment. Biotechnol. Bioeng. 2011;108: 2865–2875. © 2011 Wiley Periodicals, Inc.     

Catalytic conversion of cellulose to chemicals in ionic liquid

A simple and effective route for the production of 5-hydroxymethyl furfural (HMF) and furfural from microcrystalline cellulose (MCC) has been developed. CoSO₄ in an ionic liquid, 1-(4-sulfonic acid) butyl-3-methylimidazolium hydrogen sulfate (IL-1), was found to be an efficient catalyst for the hydrolysis of cellulose at 150 °C, which led to 84% conversion of MCC after 300 min reaction time. In the presence of a catalytic amount of CoSO₄, the yields of HMF and furfural were up to 24% and 17%, respectively; a small amount of levulinic acid (LA) and reducing sugars (8% and 4%, respectively) were also generated. Dimers of furan compounds were detected as the main by-products through HPLC-MS, and with the help of mass spectrometric analysis, the components of gas products were methane, ethane, CO, CO_2, and H₂. A mechanism for the CoSO₄-IL-1 hydrolysis system was proposed and IL-1 was recycled for the first time, which exhibited favorable catalytic activity over five repeated runs. This catalytic system may be valuable to facilitate energy-efficient and cost-effective conversion of biomass into biofuels and platform chemicals.