Residual Ionic Liquid Research Articles

Influence of residual ionic liquid on the thermal stability and electromechanical behavior of cellulose regenerated from 1-ethyl-3-methylimidazolium acetate

The regenerated cellulose films were prepared by dissolving cotton cellulose pulp directly in room temperature ionic liquid namely, 1-ethyl-3-methylimidazolium acetate at 80 °C, followed by washing/curing in different coagulants namely, methanol, deionized water, methanol-deionized water, and isopropyl alcohol-deionized water. It was found that the type of coagulants employed for curing the cellulose films has a significant influence on the amount of residual ionic liquid entrapped in the films. The amount of residual ionic liquids was 2.68, 1.01, 0.84, and 0.75 wt.% for the films cured with deionized water, isopropyl alcohol-deionized water, methanol, and methanol-deionized water, respectively. The DTG peaks of regenerated cellulose films showed two decomposition temperatures at 280 °C and 320 °C. Among all the cases studied, deionized water curing case showed the lowest decomposition temperature, attributed to entrapment of large residual ionic liquid in it. Electromechanical characteristic of the regenerated cellulose films was also investigated.

Bacterial cellulose production from cotton-based waste textiles: Enzymatic saccharification enhanced by ionic liquid pretreatment

Cotton-based waste textiles were explored as alternative feedstock for production of bacterial cellulose (BC) by Gluconacetobacter xylinus. The cellulosic fabrics were treated with the ionic liquid (IL) 1-allyl-3-methylimidazolium chloride ([AMIM]Cl). [AMIM]Cl caused 25% inactivation of cellulase activity at a concentration as low as of 0.02g/mL and decreased BC production during fermentation when present in concentrations higher than 0.0005g/mL. Therefore, removal of residual IL by washing with hot water was highly beneficial to enzymatic saccharification as well as BC production. IL-treated fabrics exhibited a 5–7-fold higher enzymatic hydrolysis rate and gave a seven times larger yield of fermentable sugars than untreated fabrics. BC from cotton cloth hydrolysate was obtained at an yield of 10.8g/L which was 83% higher than that from the culture grown on glucose-based medium. The BC from G. xylinus grown on IL-treated fabric hydrolysate had a 79% higher tensile strength than BC from glucose-based culture medium which suggests that waste cotton pretreated with [AMIM]Cl has potential to serve as a high-quality carbon source for BC production.

Rational approach to optimize cellulase mixtures for hydrolysis of regenerated cellulose containing residual ionic liquid

For the efficient production of glucose for platform chemicals or biofuels, cellulosic biomass is pretreated and subsequently hydrolyzed with cellulases. Although ionic liquids (IL) are known to effectively pretreat cellulosic biomass, the hydrolysis of IL pretreated biomass has not been optimized so far. Here, we present a semi-empirical model to rationally optimize the hydrolysis of pretreated α-cellulose – regenerated from IL and containing residual IL from the pretreatment. First, the influence of the IL MMIM DMP on the individual cellulases endoglucanase I, cellobiohydrolase I and β-glucosidase was investigated. Second, an enzyme loading-dependent model was developed to describe kinetics for the individual cellulases and cellulase mixtures. Third, this model was used to optimize the cellulase mixture for the efficient hydrolysis of regenerated cellulose containing residual IL. Finally, we could significantly increase the initial hydrolysis rate in 10% (v/v) MMIM DMP by 49% and the sugar yield by 10% points.

The Effect of Residual Ionic Liquid for Cellulose Based Electro-Active Paper Actuator

The cellulose was directly dissolved in 1-butyl-3-methylimidazolium chloride at 80°C. The clear and transparent cellulose solution was cast on the glass substrate using tape-casting method. The cast films were soaked into various solvents such as methanol, methanol-deionized water, deionized water, and isopropyl alcohol-deionized water. UV-visible transmittances were approximately 74% to 50% depending on the curing solvents. High thermal stability was observed for the cellulose film regenerated with high ratio of water content. Using these cellulose films, EAPap actuators were fabricated by coating gold-electrodes on both sides. The resonance frequency shifted to lower frequency as the amount of residual ionic liquids increased. The resonance frequency shift to lower frequency might be due to the hygroscopic nature of the ionic liquids.

High-throughput enzymatic hydrolysis of lignocellulosic biomass via in-situ regeneration

The high cost of lignocellulolytic enzymes is one of the main barriers towards the development of economically competitive biorefineries. Enzyme engineering can be used to significantly increase the production rate as well as specific activity of enzymes. However, the success of enzyme optimization efforts is currently limited by a lack of robust high-throughput (HTP) cellulase screening platforms for insoluble pretreated lignocellulosic substrates. We have developed a cost-effective microplate based HTP enzyme-screening platform for ionic liquid (IL) pretreated lignocellulose. By performing in-situ biomass regeneration in micro-volumes, we can volumetrically meter biomass (sub-mg loading) and also precisely control the amount of residual IL for engineering novel IL-tolerant cellulases. Our platform only requires straightforward liquid-handling steps and allows the integration of biomass regeneration, washing, saccharification, and imaging steps in a single microtiter plate. The proposed method can be used to screen individual cellulases as well as to develop novel cellulase cocktails.

Point by point analysis: how ionic liquid affects the enzymatic hydrolysis of native and modified cellulose

New strategies are needed to efficiently convert non-food biomass to glucose as a platform chemical. One promising approach is to use ionic liquids to first dissolve lignocellulose. Yet, in the presence of such solvents, the enzymes that catalyze cellulose hydrolysis become compromised in their activity. However, this decreased cellulase activity has not been examined in detail. Thus, the aim of this study was to investigate how the ionic liquid precisely affects cellulase activity and stability with regard to different cellulose substrates. Hereby, four ionic liquids were screened to identify which one best minimized the loss of enzyme activity. Then, this best ionic liquid was tested on one insoluble and two soluble cellulose substrates. Subsequently, the relevant parameters of solution viscosity and ionic strength were evaluated with respect to enzyme activity and stability. Finally the residual ionic liquid concentration from the precipitation of α-cellulose was varied. The best ionic liquid was found to be 1,3-dimethylimidazolium dimethylphosphate with the highest retained activity of 30% on the α-cellulose substrate in the presence of 10% (v/v) ionic liquid. Most importantly, an increase in viscosity and ionic strength contributed to the decrease in enzyme activity which nonetheless retained their stability. The hydrolysis of precipitated α-cellulose from ionic liquid showed significant higher reaction rates but reduced sugar yields when residual ionic liquid was present. None the less, it should be possible to effectively produce glucose from precipitated cellulose without needing to wash off all residual ionic liquid when optimized cellulase mixtures are used.