Regenerated Cellulose Membranes Research Articles

Hydrothermally rearranged cellulose membranes for controlled size sieving

Biodegradable polymers are important for reducing pollution and promoting sustainability as they break down more easily than traditional petroleum-based polymers. One such polymer is regenerated cellulose (RC), which is widely used in water purification and pharmaceuticals due to its chemical resistance and hydrophilicity. Since its direct use of cellulose is limited by its insolubility, derivatives like cellulose acetate (CA) are first converted through a regeneration process back into RC to make use of its functional properties. During this process, however, the membrane structure may be compromised, impairing its separation performance. Here we show that simply soaking CA membranes in hot water before regeneration significantly improves the structural integrity of RC membranes, retaining the sieving properties. The pretreatment causes planar shrinkage without disrupting the general characteristics of cellulose, allowing for sole adjustment of pore size. This straightforward approach enables precise tuning of membrane pore properties to suit specific application, such as adjusting pore size for efficient sieving of materials with particular molecular masses, all while maintaining high water permeance. Our findings suggest that hydrothermal processing has the potential to enhance the filtration performance of RC membranes and broaden their range of applications.

Development of charged membranes for the ultrafiltration of siRNA

RNA interference (RNAi) is an exciting new therapeutic approach, using small interfering RNA (siRNA) to silence specific genes for treating various diseases. Ultrafiltration has been widely used for the concentration and purification of monoclonal antibodies and other biotherapeutics; however, its application in the downstream processing of double-stranded oligonucleotides remains underexplored. This study investigates the use of ultrafiltration in the final formulation for concentrating a siRNA drug substance. Initial experiments were conducted with Ultracel™ composite regenerated cellulose membranes over a range of molecular weight cutoffs (MWCO) at different siRNA feed concentrations. Results demonstrated significant effects of both fouling and concentration polarization, with the maximum achievable concentration falling well below the target required for subcutaneous injection. Novel surface-modified ultrafiltration membranes were made by reaction of the cellulose with bromopropanesulfonic acid. These negatively charged membranes showed improved siRNA retention, reduced fouling, and a large increase in the maximum achievable siRNA concentration (from 52 to >180 mg/mL). These findings offer critical insights into novel approaches for developing high performance ultrafiltration processes for siRNA concentration.

Experimental Investigation of Regenerated Cellulose Microdialysis Probe Sterilization.

Sterilization of devices is important in hospitals, operating theatres, and emergency rooms. Microdialysis allows in vivo sampling of small molecules and is used for clinical studies. Microdialysis probes are made of soft, flexible, porous polymeric membranes. They have been traditionally disinfected using either ethanol (which fails to eliminate all microbes and doesn't satisfy regulatory requirements) or ethylene oxide gas and gamma irradiation (that are expensive and resource-intensive). In this work, three methods for microdialysis probe-sterilization were studied - autoclave and two chemicals (commercially available sterilization solutions): Sporox II and MetriCide. Following sterilization, the regenerated cellulose membranes were characterized under scanning electron microscopy and by measuring the changes in pore characteristics using nitrogen sorption. To determine the effect of sterilization on analyte diffusion through the membrane, microdialysis probes were fabricated, sterilized and tested with two analytes; ethanol and dopamine. The autoclaved membranes suffered thermo-mechanical damage and were deemed unfit for further testing. Probes sterilized with the chemical solutions were subsequently characterized by in vitro microdialysis experiments performed under regulated mass flux conditions. It is concluded that autoclaving is not a suitable sterilization technique for the cellulose membranes, while both of the chemical sterilizers were found to be good candidates for sterilization.

Beyond waste: Transforming wheat straw into oxygen and UV‐resistant cellulose films

AbstractRegenerated cellulose membrane is a biomaterial obtained by activating, dissolving, solidifying, and regenerating cellulose powder using solvents of different polarities. It has the characteristics of high oxygen resistance and high strength. However, its low water vapor barrier and single function limit its application. In order to improve the water resistance of regenerated cellulose membranes and endow them with UV resistance, lignin was extracted from waste wheat straw using formic acid method. The extracted formic acid lignin (FAL) was added to the cellulose solution to prepare a series of regenerated lignocellulosic membranes (RC‐FAL) with different lignin contents. The results indicate that lignin can not only improve the water vapor barrier, tensile strength, and water resistance of the film, but also enhance the oxygen barrier and UV absorption of the film. Compared with pure cellulose film, the contact angle of lignocellulose film can be increased by 66.2%, the UV absorption rate can reach 100%, and the oxygen transmission coefficient has no significant effect. In this paper, a new kind of biological packaging material with high oxygen resistance, strong ultraviolet absorption, and water resistance was prepared by recycling waste wheat straw, it has a broad application prospect in the industrial production of packaging materials.

Evaluation of drug release, mucoadhesive and viscoelastic performances of Netildex gel versus an antibiotic‐steroid combination system

Purpose: The poor bioavailability and therapeutic response exhibited by conventional antibiotic‐steroid ophthalmic solutions due to rapid precorneal elimination of the drug may be overcome using a gel systems. Netildex gel is a preservative‐free product based on netilmicin and dexamethasone indicated for the treatment of inflammatory ocular conditions of the anterior segment and ocular adnexa including post‐cataract surgery. The current investigation evaluated the in vitro drug release, viscosity and mucoadhesion profile of Netildex gel in comparison to a gel matrix with regard to steroid and antibiotic delivery.Methods: In vitro drug release was assessed using Franz‐type diffusion cells, under sink condition, exploiting a simulated tear solution (STS) as dissolution medium and a regenerated cellulose membrane. Evaluation of mucoadhesive and viscoelastic properties were performed by texture analyzer TA‐XT2 and rheometer.Results: The dexamethasone and netilmicin release curves in Netildex gel exhibited a better sustained and controlled pattern over an extended time period (48 h) with respect to another gel system containing anti‐inflammatory and antibiotic drugs. The results were expressed as cumulative percentage of drug release and the antibiotics‐release kinetics from the polymeric matrix, evaluated by different mathematical models. The determination of detachment force demonstrated a significant mucoadhesive strength of Netildex gel compared to mucin. Moreover, rheological analysis of Netildex gel highlighted a strong pseudo‐plastic behaviour under shear strain due to its formulation features.Conclusions: Overall, Netildex gel exhibits a sustained and controlled drug release of both dexamethasone and netilmicin from polymeric matrix thanks to its viscoelastic and mucoadhesive properties allowing to prolong drug residence time on the ocular surface. These data support the reduced administration frequency while maintaining the same efficacy and simultaneously favouring patients' compliance [1].Reference1. Mencucci R. et al. Adv Ther (2022) 39: 5474–5486.

Membrane process and adsorption on pine nut shell for removal of dye from synthetic wastewater

ABSTRACT Purification methods such as membrane technology and adsorption have been studied for the purification of textile effluents. This article aimed to evaluate the membrane separation process and adsorption on pine nut shell, separately and sequentially, for reactive dye blue 5G removal from a synthetic effluent. The membrane separation process was carried out in a front filtration module using polymeric membranes. The maximum dye retention was 35.9% using a regenerated cellulose membrane, with agitation and a pressure of 0.5 bar. The permeate flux was fully restored after cleaning the membrane. In the adsorption using pine nut shell, the best results were at pH 2, 50°C, and 50 ppm, with 85% dye removal. The Freundlich isotherm showed the best fit to the data, as did the pseudo-second-order kinetic model. The thermodynamic parameters indicated that the adsorption is of the physical type, with the process being endothermic and spontaneous. In the combined process, the permeate from the membrane separation process was subjected to adsorption on pine nut shell, achieving a removal rate of 98.7 for the initial concentration of 50 ppm. Therefore, this work shows the potential of pine nut shell as an adsorbent, not only to purify textile effluents but also to add value to a waste product, indicating that the combination of membrane technology and adsorption on pine nut shell could be an alternative for the treatment of textile effluents containing the reactive dye 5G blue.

Simultaneous generation and immobilization of silver nanoparticles on cellulose membranes by hydrogen bond-assisted in-situ reaction for colorimetric detection of mercury ions and hydrogen peroxide

The present study has verified that silver nanoparticles (AgNPs) can be simultaneously generated and immobilized in the micro-nanopores of regenerated cellulose membranes (CMs) via a simple in-situ synthesis, which can be used for colorimetric detection of mercury ions (Hg2+) and hydrogen peroxide (H2O2). The findings showed that the high-loose interpenetrating porous structure and abundant hydroxyl groups of CMs can serve as both micro-reaction spaces and immobilized sites for the in-situ synthesis of AgNPs. The Ag@CMs, composed of well-dispersed, firmly-fixed, and quantity controlled AgNPs functionalized CMs, have excellent Hg2+ colorimetric detection capabilities with a visual limit of detection (VLOD) as low as 5 nM. It can efficiently complete early-warning and semi-quantitative Hg2+ recognition, and exhibits high storage stability for more than 180 days. Moreover, the Ag@CMs exhibited peroxidase mimic behavior and catalyzed the oxidation reaction of 3,3,5,5-tetramethylbenzidine (TMB) by H2O2 to produce a blue solution. This work proposes a simple “green” approach for the heterogeneous synthesis of controllable and stable AgNPs immobilized on CMs and explores their application in chemosensing.

Intramodule pressure profiles and protein accumulation during tangential flow filtration.

Tangential flow filtration (TFF) through a 30 kDa nominal molecular weight cut-off (MWCO) ultrafiltration membrane is widely employed to concentrate purified monoclonal antibodies (mAbs) to levels required for their formulation into injectable biologics. While TFF has been used to remove casein from milk for cheese production for over 35 years, and in pharmaceutical manufacture of biotherapeutic proteins for 20 years, the rapid decline in filtration rate (i.e., flux) at high protein concentrations is a limitation that still needs to be addressed. This is particularly important for mAbs, many of which are 140-160 kDa immunoglobulin G (IgG) type proteins recovered at concentrations of 200 mg/mL or higher. This work reports the direct measurement of local transmembrane pressure drops and off-line confocal imaging of protein accumulation in stagnant regions on the surface of a 30 kDa regenerated cellulose membrane in a flat-sheet configuration widely used in manufacture of biotherapeutic proteins. These first-of-a-kind measurements using 150 kDa bovine IgG show that while axial pressure decreases by 58 psi across a process membrane cassette, the decrease in transmembrane pressure drop is constant at about 1.2 psi/cm along the 20.7 cm length of the membrane. Confocal laser scanning microscopy of the membrane surface at the completion of runs where retentate protein concentration exceeds 200 mg/mL, shows a 50 μm thick protein layer is uniformly deposited. The localized measurements made possible by the modified membrane system confirm the role of protein deposition on limiting ultrafiltration rate and indicate possible targets for improving membrane performance.

Regenerated cellulose membranes for efficient separation of organic mixtures

Organic solvent nanofiltration (OSN) is a low-carbon technology for organic mixture separation that usually relies on non-renewable fossil-derived membranes. Cellulose, a biomass material with extensive sources and superior resistance to organic solvents, holds great promise in engineering OSN membranes. Here we studied the mass transport and separation properties of regenerated cellulose membranes (RCMs), which were made from wood pulp using ionic liquid as solvent by phase inversion method. By regulating membrane thickness from 150 μm to 350 μm, the solvent permeance and solute rejection can be finely tuned. The 350-μm-thick RCM membrane (RCM-350) displays better compaction resistance than the thinner ones and harvests high solute rejection with ethanol permeance reaching ∼ 30 L m−2 h−1 bar−1, outperforming the state-of-the-art polymeric membranes and showing long-term stability during cross-flow OSN. When used for solute separation, the RCM-350 membrane provides molecular selectivity of up to 294 and 68 for Alcian blue/Rifampicin and Alcian blue/Tetracycline mixtures, respectively, which depends on the mixture composition. Our findings reveal the potential of regenerated natural cellulose as a high-performance and sustainable alternative membrane material for separating organic mixtures.

Organ-Retentive Osmotically Driven System (ORODS): A Novel Expandable Platform for in Situ Drug Delivery

Drug delivery systems capable of being retained within hollow organs allow the entire drug dose to be delivered locally to the disease site or to absorption windows for improved systemic bioavailability. A novel Organ-Retentive Osmotically Driven System (ORODS) was here proposed, obtained by assembling drug-containing units having prolonged release kinetics with osmotic units used as increasing volume compartments. Particularly, prototypes having H-shape design were conceived, manufactured and evaluated. Such devices were assembled by manually inserting a tube made of regenerated cellulose (osmotic unit) into the holes of two perforated hydrophilic tableted matrices containing paracetamol as a tracer drug. The osmotic unit was obtained by folding and gluing a plain regenerated cellulose membrane and loading sodium chloride inside. When immersed in aqueous fluids, this compartment expanded to approximately 80% of its maximum volume within 30 min of testing, and a plateau was maintained for about 6 h. Subsequently, it slowly shrank to approximately 20% of the maximum volume in 24 h, which would allow for physiological emptying of the device from hollow organs. While expanding, the osmotic unit acquired stiffness. Drug release from H-shaped ORODSs conveyed in hard-gelatin capsules was shown to be prolonged for more than 24 h.

Assessing the impact of sanitization methods for regenerated cellulose ultrafiltration/diafiltration membrane on membrane integrity and protein quality.

Ultrafiltration/diafiltration (UF/DF) is typically the final step in downstream processing of recombinant monoclonal antibody (mAb) products, which serves for protein concentration and buffer exchange. For UF/DF membranes composed of regenerated cellulose (RC), sanitization with 0.1 M sodium hydroxide is generally recommended by the supplier, but it may not be sufficient for reducing bioburden during large scale manufacturing. Therefore, more stringent sanitization methods for RC membranes are required. However, chemicals used in such sanitization step may disrupt membrane integrity, while the corresponding residuals may reduce product quality. Previous work has shown that high concentration of sodium hydroxide or addition of peracetic acid (PAA) can effectively reduce bioburden, but their effects on the RC membranes remain unknown. In this work, we assessed the impact of two sanitization methods, 0.5 M sodium hydroxide and 30 mM PAA in combination with 0.5 M sodium hydroxide, on membrane integrity and protein quality of Millipore and pall corporation (PALL) membranes. Both methods showed a similar impact as the control after performing 15 cycles. However, the addition of PAA may cause residual chemical concerns, therefore, 0.5 M sodium hydroxide was recommended as an effective and safe sanitization method for RC UF/DF membranes.

Fabrication of sandwich structure membrane and its performance for photocatalytic reduction of Cr(VI)

The regenerated cellulose membrane (RC) was synthesized by dissolving cotton cellulose in NaOH/CO(NH2)2 system. The Polydopamine/Bismuth tungstate/RC composite membrane (RCPB) with photocatalytic activity was synthesized by loading polydopamine-modified bismuth tungstate (PDA/BWO) composite onto the RC by blending method. The RCPB/PAN/RCPB sandwich structure membrane was synthesized by combining the polyacrylonitrile (PAN) nanofiber membrane and RCPB by scraping method, which can reduce aqueous Cr(VI) under visible light effectively. Characterization shows that the tensile strength, elongation at break, roughness and initial water contact angle of RCPB/PAN/RCPB are 32.1 MPa, 5.34%, 0.658 μm and 69.0°, respectively. The photoreduction percent of Cr(VI) by RCPB/PAN/RCPB can reach 99.7% within 120 min with a rate constant of 0.0869 min−1, and the photoreduction percent remains above 84.6% after four cycles. The introduction of PAN nanofiber membrane further improves the mechanical properties and recycling ability of RCPB. Meanwhile, the capture experiments reveal that the main active substance for photocatalytic reduction of Cr(VI) by RCPB/PAN/RCPB is photogenerated e−. This work provides a new idea for the treatment of Cr(VI)-containing wastewater.

Extraction and concentration of nanoplastic particles from aqueous suspensions using functionalized magnetic nanoparticles and a magnetic flow cell

Although a considerable knowledge base exists for environmental contamination from nanoscale and colloidal particles, significant knowledge gaps exist regarding the sources, transport, distribution, and effects of microplastic pollution (plastic particles < 5 mm) in the environment. Even less is known regarding nanoplastic pollution (generally considered to be plastic particles < 1 μm). Due to their small size, nanoplastics pose unique challenges and potential risks. We herein report a technique focused on the concentration and measurement of nanoplastics in aqueous systems. Hydrophobically functionalized magnetic nanoparticles (HDTMS-FeNPs) were used as part of a method to separate and concentrate nanoplastics from environmentally relevant matrices, here using metal-doped polystyrene nanoplastics (PAN-Pd@NPs) to enable low-level detection and validation of the separation technique. Using a magnetic separation flow cell, PAN-Pd@NPs were removed from suspensions and captured on regenerated cellulose membranes. Depending on the complexity of solution chemistry, variable extraction rates were possible. PAN-Pd@NPs were recovered from ultrapure water, synthetic freshwater, synthetic freshwater with a model natural organic matter isolate (NOM; Suwannee River Humic Acid), and from synthetic marine water, with recoveries for PAN-Pd@NPs of 84.9%, 78.9%, 70.4%, and 56.1%, respectively. During the initial method testing, it was found that the addition of NaCl was needed in the ultrapure water, synthetic freshwater and synthetic fresh water with NOM to induce particle aggregation and attachment. These results indicate that magnetic nanoparticles in combination with a flow-through system is a promising technique to extract nanoplastics from aqueous suspensions with various compositions.

On the edge between organic solvent nanofiltration and ultrafiltration: Characterization of regenerated cellulose membrane with aspect on dendrimer purification and recycling

The performance of commercial cellulose membranes with pore size on the border between ultra- and nanofiltration in selected organic solvents was studied focusing on rejection of small solutes and applicability for dendrimer purification. Organic markers in the MW range 100 – 700 Da and polarity range from nonpolar to polar protic compounds (aliphatics, aromatics, ethers, esters and alcohols) were used for membrane characterization. Transmission experiments in mixtures of methanol and dichloromethane of variable ratio showed the suitability of tested membranes for intended purpose, bringing information on structural factors affecting the rejection. Besides solute molar volume, its polarity type, or affinity, most conveniently expressed by Hansen solubility parameters, was found to be a crucial factor; with increasing size of solute molecule the spatial arrangement becomes also important. Solvent composition influences not only the behavior of solutes, but it also affects the membrane structure: poor solvation of cellulose by less polar solvents causes partial pore collapse, resulting in a decrease of membrane molecular weight cutoff. This effect can be used to improve the retention of a target product, as was shown for the first generation amphiphilic dendron. In addition, a simple mathematical model, allowing to estimate the course of nanofiltration and to optimize its conditions in a semicontinuous dead-end setup, is presented.

Removal of Cr(VI) by ultrafiltration enhanced by a cellulose-based soluble polymer

In this study, polymer-enhanced ultrafiltration (PEUF) was used to remove chromium ions (Cr(VI)) from water using quaternized hydroxyethyl cellulose ethoxylate (QHECE) as the extracting agent. The polymer was structurally and thermally characterized before and after loading, where Fourier transform spectra were used to corroborate the Cr(VI) binding sites. Thermogravimetric analysis showed an increase in the residual mass due to the formation of macromolecular aggregates from the water-soluble polymer (WSP) and Cr(VI). SEM/EDX was used to corroborate the presence of Cr(VI) on the WSP surface. The washing method was used to study Cr(VI) retention as a function of the solution pH, WSP quantity, pressure, Cr(VI) concentration, membrane type and presence of interfering ions (NaCl, Na2SO4 and NaHPO4) at three Cr(VI):interferent molar ratios (1:1, 1:2 and 1:4). In addition, the polymer reusability was studied over six sorption-desorption cycles. Next, the enrichment method was used to determine the maximum retention capacity of the polymer. Finally, PEUF was used to test Cr(VI) removal in simulated industrial electroplating wastewater.By varying different parameters, 92 % retention efficiency was achieved at pH 9.0 using a polymer mass of 50 mg, a pressure of 2.0 bar, an initial Cr(VI) concentration of 30 mg L−1 and a 10-kDa regenerated cellulose membrane. Increasing the Cr(VI):interferent molar ratio was found to decrease the retention efficiency, and significant decrease was obtained for the highest ratio of sulfonate ions to Cr(VI) used. Finally, the maximum retention capacity was determined to be 299.46 mg g−1 using the enrichment method, and it was demonstrated that the polymer could be reused for up to four consecutive sorption-desorption cycles.

Construction of anhydrous two-step organosolv pretreatment of lignocellulosic biomass for efficient lignin membrane-extraction and solvent recovery

Glycerol organosolv (GO) pretreatment has been revealed to be potent in selectively deconstructing the lignocellulosic biomass and effectively enhancing its enzymatic hydrolysis, but the conventional solid washing and GO lignin extraction processes frequently consume large amounts of water, resulting additionally in difficulty recycling the glycerol. In this study, an anhydrous two-step organosolv pretreatment process was explored, followed by the membrane ultrafiltration of glycerol lignin. The results showed that the solid washing of the residual glycerol after the atmospheric glycerol organosolv (AGO) pretreatment was necessary for the subsequent operation of high-solid enzymatic hydrolysis. Washing with ethanol was desirable as an alternative to water as only a low glycerol content of 5.2% resided in the substrate. Membrane ultrafiltration was helpful in extracting the AGO lignin from the pretreatment liquor, in which a high lignin extraction of 81.5% was made with a regenerated cellulose membrane (cut-off for 1 kDa) under selected ultrafiltration conditions. With the characterization of membrane-extracted lignin, it was observed for the first time that the AGO lignin has a well-preserved structure of G/S type. Moreover, the lignin was enriched with reactive groups, i.e. β-O-4′ linkages and aliphatic hydroxyl groups, which was very likely due to the glycerol grafting onto the lignin via α-etherification reaction. The two-step organosolv pretreatment process allowed 86% of glycerol and 92% of the ethanol recovery with ∼78% of distillation energy savings, which was applicable for extraction of organosolv lignin and recycling use of organic solvents.

Presence, origins and effect of stable surface hydration on regenerated cellulose for underwater oil-repellent membranes

HypothesisUnderwater oil-repellency of polyelectrolyte brushes has been attributed mainly to electric double-layer repulsion forces based on Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Many non-polyelectrolyte materials also exhibit oil-repellent behaviour, but it is not clear if there exist similar electric double-layer repulsion and if it is the sole mechanism governing their underwater oil-repellency. Experiments/simulationsIn this article, the oil-repellency of highly amorphous cellulose exhibiting is investigated in detail, through experiments and molecular dynamics simulations (MDS). FindingsIt was found that the stable surface hydration on regenerated cellulose was due to a combination of long-range electrostatic repulsions (DLVO theory) and short-range interfacial hydrogen bonding between cellulose and water molecules (as revealed by MDS). The presence of a stable water layer of about 200 nm thick (similar to that of polyelectrolyte brushes) was confirmed. Such stable surface hydration effectively separates cellulose surface from oil droplets, resulting in extremely low adhesion between them. As a demonstration of its practicality, regenerated cellulose membranes were fabricated via electrospinning, and they exhibit high oil/water separation efficiencies (including oil-in-water emulsions) as well as self-cleaning ability.

Performance investigation of hydrophilic regenerated cellulose ultrafiltration membranes with excellent anti-fouling property via hydrolysis technology

To obtain ultrafiltration (UF) membranes with excellent separation performances and antifouling properties, regenerated cellulose (RC) membranes with intrinsic hydrophilicity and dense structures immensely attract the attention of researchers. Herein, a novel modified RC membrane, which has high water permeability and antifouling capability, is prepared using cellulose acetate (CA) via non-solvent induced phase separation (NIPS) and green hydrolysis technology. The as-prepared membranes were investigated comprehensively by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) analyses and protein adsorption, etc. As a result, the RC membranes showed higher hydrophilicity (WCA=25.95°), thus they possessed a lower protein adsorption value of 1.9 ± 0.1 μg/cm2. The filtration performances were evaluated by bovine serum albumin (BSA) and endotoxin separation with dead-end filtration system. The results exhibited greater selectivity of RC membranes that BSA rejection over 98% and endotoxin remove below 0.25 EU/mL, and excellent anti-fouling properties that the flux recovery rate (FRR) over 95% and even as high as 100%. Simultaneously, the common polyethersulfone (PES) composite membranes were prepared via NIPS technology, and comprehensively compared with RC membranes to provide a theoretical basis for the practical application of RC membranes in pharmaceutical and biotechnological industries.

Heat-Resistant, Robust, and Hydrophilic Separators Based on Regenerated Cellulose for Advanced Supercapacitors.

Separators in supercapacitors (SCs) typically suffer from defects of low mechanical property, limited ion transport, and electrolyte wettability, and poor thermal stability, impeding the development of SCs. Herein, high-performance regenerated cellulose (RC) based separators are designed that are fabricated by effective hydrolytic etching of inorganic CaCO3 nanoparticles from a filled RC membrane. The as-prepared RC separator displays excellent comprehensive performances such as higher tensile strength (75.83MPa) and thermal stability (200°C), which is superior to commercial polypropylene-based separator (Celgard 2500) and sufficient to maintain their structural integrity even at temperatures in excess of 200°C. Benefiting from its hydrophilicity, high porosity, and outstanding electrolyte uptake rate (208.5%), the RC separator exhibits rapid transport and permeability of ions, which is 2.5× higher than that of the commercial nonwoven polypropylene separator (NKK -MPF30AC-100) validated by electrochemical tests in the 1.0m Na2 SO4 electrolyte. Results show that porous RC separator with unique advantages of superior electrolyte wettability, mechanical robustness, and high thermal stability, is a promising separator for SCs with high-performance and safety.

Immobilization of Recombinant Endoglucanase (CelA) from Clostridium thermocellum on Modified Regenerated Cellulose Membrane

Cellulases are being widely employed in lignocellulosic biorefineries for the sustainable production of value-added bioproducts. However, the high production cost, sensitivity, and non-reusability of free cellulase enzymes impede their commercial applications. Enzyme immobilization seems to be a potential approach to address the aforesaid complications. The current study aims at the production of recombinant endoglucanase (CelA) originated from the cellulosome of Clostridium thermocellum in Escherichia coli (E. coli), followed by immobilization using modified regenerated cellulose (RC) membranes. The surface modification of RC membranes was performed in two different ways: one to generate the immobilized metal ion affinity membranes RC-EPI-IDA-Co2+ (IMAMs) for coordination coupling and another to develop aldehyde functional group membranes RC-EPI-DA-GA (AMs) for covalent bonding. For the preparation of IMAMs, cobalt ions expressed the highest affinity effect compared to other metal ions. Both enzyme-immobilized membranes exhibited better thermal stability and maintained an improved relative activity at higher temperatures (50–90 °C). In the storage analysis, 80% relative activity was retained after 15 days at 4 °C. Furthermore, the IMAM- and AM-immobilized CelA retained 63% and 53% relative activity, respectively, after being reused five times. As to the purification effect during immobilization, IMAMs showed a better purification fold of 3.19 than AMs. The IMAMs also displayed better kinetic parameters, with a higher Vmax of 15.57 U mg−1 and a lower Km of 36.14 mg mL−1, than those of AMs. The IMAMs were regenerated via treatment with stripping buffer and reloaded with enzymes and displayed almost 100% activity, the same as free enzymes, up to 5 cycles of regeneration.