Enabling the utilization of wool as an enzyme support: Enhancing the activity and stability of lipase immobilized onto woolen cloth

Polypyrrole- and Polyaniline-Coated Cotton Fabrics as Efficient Adsorbents for the Pharmaceutical Water Contaminants Diclofenac and Salicylic Acid

The emerging pharmaceutical contaminants diclofenac (DCF) and salicylic acid (SA) pose potential hazards to humans and living organisms due to their persistence in water environments. In this work, the conductive polymers polypyrrole (PPY) and polyaniline (PANI) were successfully coated on cotton fabrics, as confirmed by FTIR and SEM measurements. The coated fabrics efficiently removed DCF at pH 5.3 and SA at pH 4, with removal efficiencies that exceeded 90% and 70%, respectively. Adsorption was rapid for most of the tested contaminant-fabric systems and reached equilibrium within 20-30 min. The best adsorption performance for both contaminants was shown on the PPY-coated fabrics, which yielded adsorption capacities of about 65 and 21 mg/g for DCF and SA, respectively. This could be explained by molecular modeling simulations, which mostly estimated higher total cohesive energy densities for adsorption on the PPY-coated fabrics than on the PANI-coated ones. The adsorption mechanism involved both coulombic electrostatic attractions and non-coulombic van der Waals and π-π stacking. The fabrics could be reused for three adsorption-desorption cycles. Immobilization of the conductive polymers on cotton fabrics provides a facile method for their handling and collection during adsorption and regeneration cycles while maintaining their multi-functionality in adsorbing different contaminants.

Surface Functionalization of Wool via Microbial-Transglutaminase as Bio-Mordant to Improve Dyeability with Madder in the Presence of Alum

Herein, the wool fabric was mordanted with alum, treated with microbial transglutaminase (m-TGase), and then dyed with madder. Different concentrations of alum and m-TGase were used to find out the optimum condition to achieve the best color after dyeing the wool fabrics with aqueous extract of madder. FT-IR spectroscopy and scanning electron microscopy (SEM) methods were applied to characterize the as-prepared samples. Contact angle measurements showed that the water uptake capability was increased in the case of the wool sample treated with alum and enzyme. Moreover, the samples were assessed for color strength (K/S) and color fastness. Our results showed that the optimal condition to get the highest color value was for the sample with 10% owf (of weight of fabric) alum and 5% owf m-TGase. Furthermore, it was found that there was a critical concentration for enzyme so that an increase in m-TGase amount would cause damage to the scales of fibers. The best condition of the dyeing process was discussed in this study, and also the proposed mechanism was presented. Indeed, treatment of wool with m-TGase led to a reduction in the amount of consumed alum, while investigations in color performances demonstrated the enhancement in color fastness, as well as color strength.

Enzymatic esterification of oleic acid by Candida rugosa lipase immobilized onto biochar

The immobilization of Candida rugosa lipase (CRL) onto biochar was studied in a series of batch experiments. CRL sorption behavior was evaluated as a function of pH, enzyme concentration, temperature and ionic strength. As the immobilized lipase was used for the catalytic esterification of oleic acid, its resistance to solvents and thermal stability were evaluated. CRL adsorption increased by increasing temperature, and with higher pH, reaching a maximum at pH 7.0. Immobilization increased lipase stability at 40 °C by more than 80% when compared to the free enzyme. Moreover, immobilized CRL showed high stability in the presence of tert-butanol, which prevents premature deactivation of the enzyme caused by alcohols during the reaction. Immobilization of CRL increased the oleic acid conversion rate. Our results suggest that biochar is a highly promising material for the immobilization of CRL lipase for the catalytic production of esters.

Immobilization and stabilization of alcohol dehydrogenase on polyvinyl alcohol fibre

A polyvinyl alcohol (PVA) fibrous carrier has been chemically modified for the immobilization of yeast alcohol dehydrogenase (ADH) with an aim to increase its stability over a wide pH range, prolong its activity upon storage, and enhance its reusability. The strategy for immobilization involved functionalization of the fibrous carrier with chloropropinoyl chloride followed by amination with ethylenediamine. Tethering of the ADH enzyme to the PVA scaffold was achieved with glutaraldehyde. The activity profile of the immobilized enzyme was compared to soluble enzyme as a function of pH, temperature and reusability. The immobilization of ADH on PVA fibrous carrier shifted the optimal reaction pH from 7 to 9, and improved the thermostability at 60 °C. Furthermore, the immobilized enzyme retained 60% of its original activity after eight cycles of reuse. These results demonstrate that PVA based textiles can serve as a flexible, reusable carrier for enzyme immobilization.

Biocatalysts based on nanozeolite-enzyme complexes: Effects of alkoxysilane surface functionalization and biofuel production using microalgae lipids feedstock

Nanozeolites with different crystallographic structures (Nano/TS1, Nano/GIS, Nano/LTA, Nano/BEA, Nano/X, and Nano-X/Ni), functionalized with (3-aminopropyl)trimethoxysilane (APTMS) and crosslinked with glutaraldehyde (GA), were studied as solid supports for Thermomyces lanuginosus lipase (TLL) immobilization. Physicochemical characterizations of the surface-functionalized nanozeolites and nanozeolite-enzyme complexes were performed using XRD, SEM, AFM, ATR-FTIR, and zeta potential measurements. The experimental enzymatic activity results indicated that the nanozeolitic supports functionalized with APTMS and GA immobilized larger amounts of enzymes and provided higher enzymatic activities, compared to unfunctionalized supports. Correlations were observed among the nanozeolite surface charges, the enzyme immobilization efficiencies, and the biocatalyst activities. The catalytic performance and reusability of these enzyme-nanozeolite complexes were evaluated in the ethanolysis transesterification of microalgae oil to fatty acid ethyl esters (FAEEs). TLL immobilized on the nanozeolite supports functionalized with APTMS and GA provided the most efficient biocatalysis, with FAEEs yields above 93% and stability during five reaction cycles. Lower FAEEs yields and poorer catalytic stability were found for nanozeolite-enzyme complexes prepared only by physical adsorption. The findings indicated the viability of designing highly efficient biocatalysts for biofuel production by means of chemical modulation of nanozeolite surfaces. The high biocatalyst catalytic efficiency observed in ethanolysis reactions using a lipid feedstock that does not compete with food production is an advantage that should encourage the industrial application of these biocatalysts.

Polyethylenimine: a very useful ionic polymer in the design of immobilized enzyme biocatalysts

This review discusses the possible roles of polyethylenimine (PEI) in the design of improved immobilized biocatalysts from diverse perspectives.

Immobilization of Lipase from Pseudomonas fluorescens on Porous Polyurea and Its Application in Kinetic Resolution of Racemic 1-Phenylethanol

A porous polyurea (PPU) was prepared through a simple protocol by reacting toluene diisocyanate with water in binary solvent of water-acetone. Its amine group was determined through spectrophotometric absorbance based on its iminization with p-nitrobenzaldehyde amines. PPU was then used as a novel polymer support for enzyme immobilization, through activation by glutaraldehyde followed by immobilization of an enzyme, lipase from Pseudomonas fluorescens (PFL), via covalent bonding with the amine groups of lipase molecules. Influences of glutaraldehyde and enzyme concentration and pH in the process were studied. The results revealed that the activity of the immobilized PFL reached a maximum at GA concentration of 0.17 mol/L and at pH 8. Immobilization rate of 60% or higher for PFL was obtained under optimized condition with an enzyme activity of 283 U/mg. The porous structure of PPU, prior to and after GA activation and PFL immobilization, was characterized. The activity of the immobilized PFL at different temperature and pH and its stability at 40 °C as well as its reusability were tested. The immobilized enzyme was finally used as enantioselective catalyst in kinetic resolution of racemic 1-phenylethanol (1-PEOH), and its performance compared with the free PFL. The results demonstrate that the enzyme activity and stability were greatly improved for the immobilized PFL, and highly pure enantiomers from racemic 1-PEOH were effectively achieved using the immobilized PFL. Noticeable deactivation of PFL in the resolution was observed by acetaldehyde in situ formed. In addition, the immobilized PFL was readily recovered from the reaction system for reuse. A total of 73% of the initial activity was retained after 5 repeated reuse cycles. This work provides a novel route to preparation of a polyurea porous material and its enzyme immobilization, leading to a novel type of immobilized enzyme for efficient kinetic resolution of racemic molecules.

Immobilization of lipase on woolen fabrics: enhanced effectiveness in stain removal

The aim of this research was to examine the effectiveness of an enzyme in enhancing the cleaning effectiveness of woolen fabric without addition of any detergent. As a model enzyme, lipase from Pseudomonas fluoresces was immobilized onto a woolen cloth using a unique protocol that involved: chlorination of the wool, adsorbing a polyethyleneimine (PEI) spacer, adsorbing, and cross-linking with glutaraldehyde (GA) followed by adsorption of the lipase. It was determined that for this protocol, the immobilized activity was dependent on the GA solution pH and not on its concentration. The cloth exhibited excellent oily stain removal ability: after being stained with olive oil and stored for 1 day in air at room temperature, the oily stain could be easily removed by 0.05 M pH 8.5 Tris buffer without any detergent addition. This enhanced cleaning was stable also over a period of one month. The activity of the cloth (based on activity assay) dropped considerably over just 15 days storage in air. This therefore likely indicates that the enhanced cleaning seen over an extended storage period may not require as high an enzyme activity. The activity of the immobilized lipase was also very stable when stored under near ideal conditions: when the immobilized cloth was stored in 0.05 M Tris buffer (pH 8.5) for more than 80 days in a refrigerator, more than 80% of the lipase activity remained. Overall, results indicate that this immobilization protocol is a promising step towards producing a woolen fabric with enhanced cleaning properties.

Immobilization of Amano Lipase A onto Stöber silica surface: process characterization and kinetic studies

The immobilization of Amano Lipase A from Aspergillus niger by adsorption onto Stöber silica matrix obtained by sol-gel method was studied. The effectiveness of the enzyme immobilization and thus the usefulness of the method was demonstrated by a number of physicochemical analysis techniques including Fourier Transform Infrared Spectroscopy (FT-IR), elemental analysis (EA), thermogravimetric analysis (TG), porous structure of the support and the products after immobilization from the enzyme solution with various concentration at different times. The analysis of the process’ kinetics allowed the determination of the sorption parameters of the support and optimization of the process. The optimum initial concentration of the enzyme solution was found to be 5 mg mL-1, while the optimum time of the immobilization was 120 minutes. These values of the variable parameters of the process were obtained by as ensuring the immobilization of the largest possible amount of the biocatalyst at