Biocatalytic Membrane Research Articles

Biocatalytic membrane reactor modeling for fermentative hydrogen production from wastewater: A review

Biocatalytic membrane reactor modeling for fermentative hydrogen production from wastewater: A review

Biocatalytic Membranes for Carbon Capture and Utilization.

Innovative carbon capture technologies that capture CO2 from large point sources and directly from air are urgently needed to combat the climate crisis. Likewise, corresponding technologies are needed to convert this captured CO2 into valuable chemical feedstocks and products that replace current fossil-based materials to close the loop in creating viable pathways for a renewable economy. Biocatalytic membranes that combine high reaction rates and enzyme selectivity with modularity, scalability, and membrane compactness show promise for both CO2 capture and utilization. This review presents a systematic examination of technologies under development for CO2 capture and utilization that employ both enzymes and membranes. CO2 capture membranes are categorized by their mode of action as CO2 separation membranes, including mixed matrix membranes (MMM) and liquid membranes (LM), or as CO2 gas-liquid membrane contactors (GLMC). Because they selectively catalyze molecular reactions involving CO2, the two main classes of enzymes used for enhancing membrane function are carbonic anhydrase (CA) and formate dehydrogenase (FDH). Small organic molecules designed to mimic CA enzyme active sites are also being developed. CO2 conversion membranes are described according to membrane functionality, the location of enzymes relative to the membrane, which includes different immobilization strategies, and regeneration methods for cofactors. Parameters crucial for the performance of these hybrid systems are discussed with tabulated examples. Progress and challenges are discussed, and perspectives on future research directions are provided.

Bactericidal and biocatalytic temperature responsive microgel based self-cleaning membranes for water purification

The present study focuses on creating an antimicrobial and biocatalytic smart gating membrane by synthesizing unique core–shell microgels. The core–shell microgels are synthesized by grafting short chains of poly(ethylenimine) (PEI) onto a poly((N-isopropyl acrylamide)–co-glycidyl methacrylate)) (P(NIPAm-co-GMA)) core. Subsequently, the produced microgels are utilized as a substrate for synthesizing and stabilizing silver nanoparticles (Ag NPs) through an in-situ approach. These Ag NPs immobilized microgels are then suction filtered over a polyethylene terephthalate (PET) track-etched support to create cross-linked composite microgel membranes (CMMs). After structural and permeation characterization of the prepared CMMs, the laccase enzyme is then covalently grafted to the surface of the membrane and tested for its effectiveness in degrading Reactive red-120 dye. The laccase immobilized biocatalytic CMMs show effective degradation of the Reactive red-120 by 71%, 48%, and 34% at pH 3, 4, and 5, respectively. Furthermore, the immobilized laccase enzyme showed better activity and stability in terms of thermal, pH, and storage compared to the free laccase, leading to increased reusability. The unique combination of Ag NPs and laccase on a thermoresponsive microgel support resulted in a responsive self-cleaning membrane with excellent antimicrobial and dye degradation capabilities for environmentally friendly separation technology.

Engineering polyelectrolyte multilayer coatings as a strategy to optimize enzyme immobilization on a membrane support

This study presents a systematic design of a biocatalytic membrane reactor, where we combined physical adsorption and chemical conjugation of Alcohol Dehydrogenase (ADH) in a novel type of polyelectrolyte (PE) layer-by-layer (LbL) assembly system. The hybrid LbL structure is proposed as a strategy to simultaneously advance activity and operational stability of enzymes immobilized on a membrane surface. Using poly(allylamine hydrochloride) (PAH) and poly(methacrylic acid) sodium salt (PMAA) allowed functionalization of polysulfone (Psf) membrane for subsequent ADH immobilization with no resistance to substrate mass transfer and no decrease in water permeability (WP) (56.5 ± 8.8 Lm−2h −1bar−1) compared to the pristine membrane (50.8 ± 1.7 Lm−2h−1bar−1). Tailoring membrane surface chemistry, enzyme concentration, time, and pH during the adsorption step allowed to increase specific activity of the biocatalytic membrane from 1.13 ± 0.18 mU/cm2 for immobilization on the pristine membrane to 4.09 ± 0.53 mU/cm2 for immobilization on a PAH-modified coating. Conjugation of adsorbed ADH with PMAA layer improved reusability compared to the non-conjugated membrane (by retaining 73.4 ± 3.2% of the starting activity on the third conversion run against 58.7 ± 2.4%) and shifted pH optimum by 1 unit compared to the free ADH. The presented approach of LbL assembly synthesis provides a potential foundation for engineering of biocatalytic nanoscale reactors.

Regenerable graft of laccase on glycosylated membrane for treatment of aquatic micropollutants

Biocatalytic membranes with convenient assembly and favorable activity regeneration are highly desired for practical water treatment. Herein, glycosylated membrane has been developed as a regenerable matrix for immobilizing laccase via specific carbohydrate-protein recognition, using Concanavalin A as the bridge. The laccase-immobilized biocatalytic membranes have been successfully used to treat aquatic micropollutants. Plenty of saccharide units are introduced to the surface of substrate, contributing to enhance hydrophilicity. The removal ratio of bisphenol A (BPA) is significantly improved thanks to the pore narrowing effect and laccase-induced degradation process. Moreover, the biocatalytic membrane could be rapidly regenerated by chemical rinsing and the lectins are also able to be reloaded. As a result, thus-prepared biocatalytic membrane can be repeatedly used with good BPA removal for 8 cycles. This work not only presents a simple and reliable method to make glycosylated membrane, but also provides a guidance of biocatalytic membranes for water treatment.

Hydrophilic metal-chelated membrane for biocatalytic membrane reactor application

Hydrophilic metal-chelated membrane for biocatalytic membrane reactor application

Study of Membrane-Immobilized Oxidoreductases in Wastewater Treatment for Micropollutants Removal.

The development of efficient strategies for wastewater treatment to remove micropollutants is of the highest importance. Hence, in this study, we presented a rapid approach to the production of biocatalytic membranes based on commercially available cellulose membrane and oxidoreductase enzymes including laccase, tyrosinase, and horseradish peroxidase. Effective enzyme deposition was confirmed based on Fourier transform infrared spectra, whereas results of spectrophotometric measurements showed that immobilization yield for all proposed systems exceeded 80% followed by over 80% activity recovery, with the highest values (over 90%) noticed for the membrane-laccase system. Further, storage stability and reusability of the immobilized enzyme were improved, reaching over 75% after, respectively, 20 days of storage, and 10 repeated biocatalytic cycles. The key stage of the study concerned the use of produced membranes for the removal of hematoporphyrin, (2,4-dichlorophenoxy)acetic acid (2,4-D), 17α-ethynylestradiol, tetracycline, tert-amyl alcohol (anesthetic drug), and ketoprofen methyl ester from real wastewater sampling at various places in the wastewater treatment plant. Although produced membranes showed mixed removal rates, all of the analyzed compounds were at least partially removed from the wastewater. Obtained data clearly showed, however, that composition of the wastewater matrix, type of pollutants as well as type of enzyme strongly affect the efficiency of enzymatic treatment of wastewater.

Laccase immobilization in polyelectrolyte multilayer membranes for 17α-ethynylestradiol removal: Biocatalytic approach for pharmaceuticals degradation.

Enzymatic membrane reactors equipped with multifunctional biocatalytic membranes are promising and sustainable alternatives for removal of micropollutants, including steroid estrogens, under mild conditions. Thus, in this study an effort was made to produce novel multifunctional biocatalytic polyelectrolyte multilayer membranes via polyelectrolyte layer-by-layer assembly with laccase enzyme immobilized between or into polyelectrolyte layers. In this study, multifunctional biocatalytic membranes are considered as systems composed of commercially available filtration membrane modified by polyelectrolytes and immobilized enzymes, which are produced for complex treatment of water pollutants. The multifunctionality of the proposed systems is related to the fact that these membranes are capable of micropollutants removal via simultaneous catalytic conversion, membrane adsorption and membrane rejection making remediation process more complex, however, also more efficient. Briefly, cationic poly-l-lysine and polyethylenimine as well as anionic poly(sodium 4-styrenesulfonate) polyelectrolytes were deposited onto NP010 nanofiltration and UFX5 ultrafiltration membranes to produce systems for removal of 17α-ethynylestradiol. Images from scanning electron microscopy confirm effective enzyme deposition, whereas results of zeta potential measurements indicate introduction of positive charge onto the membranes. Based on preliminary results, four membranes with over 70%, activity retention produced using polyethylenimine in internal and entrapped mode, were selected for degradation tests. Systems based on UFX5 membrane allowed over 60% 17α-ethynylestradiol removal within 100min, whereas NP010-based systems removed over 75% of estrogen within 150min. Further, around 80% removal of 17α-ethynylestradiol was possible from the solutions at concentration up to 0.1mg/L at pH ranging from 4 to 6 and at the pressure up to 3bar, indicating high activity of the immobilized laccase over wide range of process conditions. Produced systems exhibited also great long-term stability followed by limited enzyme elution from the membrane. Finally, removal of over 70% and 60% of 17α-ethynylestradiol, respectively by NP010 and UFX5 systems after 8 cycles of repeated use indicate high reusability potential of the systems and suggest their practical application in removal of micropollutants, including estrogens.

Facile fabrication of flexible ceramic nanofibrous membranes for enzyme immobilization and transformation of emerging pollutants

Biocatalytic nanofibrous membranes, integrating the benefits of membranes and enzymes, have drawn attention in wastewater treatment because of their efficient catalytic performance and operational catalytic stability. However, these membranes are typically polymeric membranes, and their fate as plastic waste is not considered environmentally sustainable. By contrast, ceramic-based membranes are considered more environmental-friendly due to their low-risk recycling and disposal procedures, but the brittleness of these membranes limits their implementation. Here, we report the fabrication of high flexibility SiO2 biocatalytic nanofiber membranes (NFMs) and their previously unreported application in emerging pollutant bioremediation. We used a commercial laccase (EC 1.10.3.2) as a model biocatalyst to evaluate the impact of different strategies to improve the catalytic properties of the NFMs in terms of enzyme load and apparent activity per membrane weight. Enzyme immobilization with the co-deposition of polydopamine (PDA) and polyethyleneimine (PEI) resulted in the best immobilization yield (57.9 ± 0.5 %) and apparent activity of 6.4 ± 1.1 U g−1 membrane. Compared to the free enzyme, the fabricated bio-catalytic membranes maintained 80 % of residual activity after five cycles. In addition, the membranes exhibited > 95 % depletion of the five emerging pollutants diclofenac, mefenamic acid, benzefabrite, bicalutamide, and clarithromycin. The successful fabrication of flexible biocatalytic ceramic membranes holds promise as a new technological platform for sustainable wastewater treatment and brings novel insights into a previously less explored realm of membrane applications.

Reagent-Free Immobilization of Industrial Lipases to Develop Lipolytic Membranes with Self-Cleaning Surfaces.

Biocatalytic membrane reactors combine the highly efficient biotransformation capability of enzymes with the selective filtration performance of membrane filters. Common strategies to immobilize enzymes on polymeric membranes are based on chemical coupling reactions. Still, they are associated with drawbacks such as long reaction times, high costs, and the use of potentially toxic or hazardous reagents. In this study, a reagent-free immobilization method based on electron beam irradiation was investigated, which allows much faster, cleaner, and cheaper fabrication of enzyme membrane reactors. Two industrial lipase enzymes were coupled onto a polyvinylidene fluoride (PVDF) flat sheet membrane to create self-cleaning surfaces. The response surface methodology (RSM) in the design-of-experiments approach was applied to investigate the effects of three numerical factors on enzyme activity, yielding a maximum activity of 823 ± 118 U m−2 (enzyme concentration: 8.4 g L−1, impregnation time: 5 min, irradiation dose: 80 kGy). The lipolytic membranes were used in fouling tests with olive oil (1 g L−1 in 2 mM sodium dodecyl sulfate), resulting in 100% regeneration of filtration performance after 3 h of self-cleaning in an aqueous buffer (pH 8, 37 °C). Reusability with three consecutive cycles demonstrates regeneration of 95%. Comprehensive membrane characterization was performed by determining enzyme kinetic parameters, permeance monitoring, X-ray photoelectron spectroscopy, FTIR spectroscopy, scanning electron microscopy, and zeta potential, as well as water contact angle measurements.

Biocatalytic polymeric membranes to decrease biofilm fouling and remove organic contaminants in wastewater: a review

Biocatalytic polymeric membranes to decrease biofilm fouling and remove organic contaminants in wastewater: a review

Biocatalytic membranes through aqueous phase separation

HypothesisPolymer membranes play a critical role in water treatment, chemical industry, and medicine. Unfortunately, the current standard for polymer membrane production requires unsustainable and harmful organic solvents. Aqueous phase separation (APS) has recently been proposed as a method to produce membranes in a more sustainable manner through induced polyelectrolyte complexation in aqueous solutions. ExperimentsWe demonstrate that APS has another natural advantage that goes beyond sustainability: the easy incorporation of enzymes in the membrane structure. Biocatalytic membranes hold great promise in for example biorefinery, but the most common current post-production processes to immobilize enzymes on the membrane surface are complicated and expensive. FindingsIn this study we demonstrated the first biocatalytic membrane produced via APS. We demonstrate an easy procedure to incorporate lysozyme in polyelectrolyte complex membranes made via APS. Our functionalized membranes have the same structure, water permeability (in the range of high nanofiltration, low ultrafiltration), and retention as membranes without lysozyme. Lysozyme is antibacterial by catalysing the hydrolysis of specific peptidoglycan bonds in bacteria walls. We demonstrate that the functionalized membranes are also capable of catalysing this reaction. The membranes remain enzymatically active for a period of at least one week. This opens new routes to produce polymer membranes with added biological function.

Biocatalytic membranes in anti-fouling and emerging pollutant degradation applications: Current state and perspectives

• Biocatalytic membrane processes produce environmentally friendly and energy-efficient processes. • Enzyme immobilization is the simplest solution to long-term operational stability, activity and reuse. • Modified immobilization methods improve the performance of enzymes over common immobilization methods. • Biocatalytic membranes compared with electrocatalytic and photocatalytic membrane processes. • Biocatalytic membranes have the potential to be used in antifouling and emerging pollutant degradation applications. Biocatalytic membranes, which are fabricated by taking advantage of the synergetic effect of membranes and enzymes, have been one of the attractive treatment methods as sustainable and environmentally friendly. In biocatalytic membrane systems, enzymes can be free or immobilized, but the number of immobilized applications increases due to the advantages of immobilization. Immobilization is one of the critical points to improve the storage and operational stability of enzymes. Additionally, immobilized enzymes have a significant benefit over free enzymes in terms of reusability. This review summarizes recent advances in the preparation of biocatalytic membranes with the different immobilization methods of enzymes in/on membranes, paying particular attention to recent approaches for anti-fouling and emerging pollutant degradation applications. Also, some future outlooks were briefly presented.

Hybrid enzymatic CO2 capture process in intensified flat sheet membrane contactors with immobilized carbonic anhydrase

A hybrid enzymatic CO2 absorption process in an intensified flat sheet membrane contactor with immobilized human carbonic anhydrase II (hCA II) enzyme was proposed. In addition to be immobilized on the membrane surface, extra carbonic anhydrase enzyme was immobilized on the surface of magnetic nanoparticles (MNPs) dispersed in the liquid phase to reduce the mass transfer limitations and enhance the absorption process. This hybrid enzymatic process is beneficial to attain high CO2 absorption rates, even if a component of the enzymatic system, either the biocatalytic membrane or biocatalytic MNPs, does not operate appropriately. The improvement CO2 hydration in the presence of biocatalytic MNPs was more significant at lower CA loadings on membrane surface. Reusability of the biocatalytic membranes and biocatalytic MNPs was demonstrated by 10 absorption cycles and the intensified membrane contactor displayed stable operation for several hours. A multiscale mathematical model (under gas-filled or partially liquid-filled membrane pores conditions) was proposed to explore the behaviour of the intensified membrane contactor. Model simulations showed that the resistance to mass transfer in membrane wetted zones is overcame by the CO2 enzymatic absorption in these zones (catalyzed by enzyme immobilized in membrane pores) and possible by the absorption of CO2 in the presence of biocatalytic MNPs.

Selective Coimmobilization of His-Tagged Enzymes on Yttrium-Stabilized Zirconia-Based Membranes for Continuous Asymmetric Bioreductions.

Scalability, process control, and modularity are some of the advantages that make flow biocatalysis a key-enabling technology for green and sustainable chemistry. In this context, rigid porous solid membranes hold the promise to expand the toolbox of flow biocatalysis due to their chemical stability and inertness. Yttrium-stabilized zirconia (YSZ) fulfills these properties; however, it has been scarcely exploited as a carrier for enzymes. Here, we discovered an unprecedented interaction between YSZ materials and His-tagged enzymes that enables the fabrication of multifunctional biocatalytic membranes for bioredox cascades. X-ray photoelectron spectroscopy suggests that enzyme immobilization is driven by coordination interactions between the imidazole groups of His-tags and both Zr and Y atoms. As model enzymes, we coimmobilized in-flow a thermophilic hydroxybutyryl-CoA dehydrogenase (TtHBDH-His) and a formate dehydrogenase (His-CbFDH) for the continuous asymmetric reduction of ethyl acetoacetate with in situ redox cofactor recycling. Fluorescence confocal microscopy deciphered the spatial organization of the two coimmobilized enzymes, pointing out the importance of the coimmobilization sequence. Finally, the coimmobilized system succeeded in situ, recycling the redox cofactor, maintaining the specific productivity using only 0.05 mM NADH, and accumulating a total enzyme turnover number of 4000 in 24 h. This work presents YSZ materials as ready-to-use carriers for the site-directed enzyme in-flow immobilization and the application of the resulting heterogeneous biocatalysts for continuous biomanufacturing.

Regenerable temperature-responsive biocatalytic nanofiltration membrane for organic micropollutants removal

SummaryBiocatalytic nanofiltration membranes (BNMs) exhibit great potentials in organic micropollutants removal attributed to its synergistic effect between enzyme catalysis and membrane separation. However, the difficulties in regeneration of the BNMs halted their economic practicality. Inspired by cell membranes with stimuli-responsive channels, we have developed the temperature-responsive BNMs with nanogating function by poly(N-isopropyl acrylamide) (PNIPAM) modification. PNIPAM modification increases the geometric confinement of the support layer to enzymes, thus improving enzyme loading, inhibiting enzyme leakage, and preventing membrane permeability decline caused by enzyme excess migration and aggregation. By optimizing the concentration of reaction monomers, modification time, and strategies, the PNIPAM-based BNMs show high bisphenol A (BPA) removal efficiency and long-term stability. Furthermore, the PNIPAM-polyethyleneimine-based BNMs can be easily regenerated at 38°C, and the laccase activity and BPA removal efficiency are fully recovered. This work would promote the real application of BNMs in bioconversion, drug delivery, and biosensors.

Removal of tetracycline in enzymatic membrane reactor: Enzymatic conversion as the predominant mechanism over adsorption and membrane rejection

The presence of micropollutants such as dyes, pharmaceuticals, personal care products or estrogens in water and wastewater might have an adverse effect on the environment and human beings. There is thus an emerging need to detect and remove these compounds from wastewater and water. Our study, which is strongly embedded in the scientific trend of development of novel, efficient and eco-friendly methods for removal of micropollutants, concerns fabrication of novel biocatalytic membranes with immobilized laccase for degradation of tetracycline. Biocatalytic membranes were prepared in normal mode using pressure-driven laccase immobilization and in reverse mode using reverse-fouling enzyme immobilization. Both biocatalytic membranes showed over 70% activity retention and exhibited over 80% of initial activity after 20 days of storage. The use of the produced systems facilitates removal of over 70% of tetracycline at pH from 3 to 5 from solution at concentrations up to 5 mg L−1 in a in flow-through mode at a pressure of 3 bar. However, 89% removal efficiency of antibiotic was observed with the membrane in normal mode. The results highlight that a high biodegradation rate was attained due to synergistic action of membrane rejection, adsorption by polydopamine and membrane, and enzymatic conversion where laccase oxidation was the most pronounced. Due to application of membrane separation, a final effluent of significantly lower toxicity was obtained compared to the parent solution. The data presented indicate that the biocatalytic membranes produced could be considered as promising environmental tools for removal of micropollutants from wastewater and water bodies.

Biocatalytic metal–organic framework membrane towards efficient aquatic micropollutants removal

The micropollutants in water sources are harmful to the aquatic environment and human health, and remain a significant challenge to be completely eliminated by conventional processes. Here, an original biocatalytic enzyme/metal–organic framework (MOF) composite membrane is developed to facilitate continuous and efficient removal of micropollutants from aqueous solution. In this work, an in-situ biomineralization strategy of simultaneous MOF (zeolitic imidazolate framework-8 or ZIF-8) nucleation and immobilization of horseradish peroxidase (HRP) is employed to form an enzymatic reactive HRP@ZIF-8 layer on modified ultrafiltration membrane. Such a hybrid structure design successfully integrates selective separation with stable enzymatic catalysis to prepare a reactive molecular sieve membrane, which realizes desirable decontamination performance toward micropollutants under low pressure. The as-prepared membrane sets a new record of bisphenol A (BPA) removal efficiency of 98% accompanied with high permeance (~33.32 L/m2.h.bar) at continuous mode. The removal mechanism is considered to be a combination of enhanced adsorption by MOFs enriching BPA molecules near the enzymes, catalytic oxidation by enzymes breaking the adsorption saturation limitation, and also membrane retention that reduced the enzymatic burden. In addition, the biocatalytic membrane displays enhanced stability and reusability due to the protection effect by the ZIF-8 exoskeleton, demonstrating good potential for stable and efficient removal of micropollutants for water treatment.

Immobilization of naringinase on asymmetric organic membranes: Application for debittering of grapefruit juice

An enzymatic membrane reactor (EMR) is assembled for the immobilization of naringinase on a polyethersulfone ultrafiltration membrane, based on fouling-induced method. The effects of molecular weight cut-off, membrane configuration, applied pressure, enzyme concentration and pH are studied in terms of permeate rate, immobilization efficiency, and biocatalytic conversion. The 10 kDa membrane operating in reverse mode, 0.2 MPa, 0.3 gL−1 of enzyme in acetate buffer at pH 5 and cross-linking with 0.25% glutaraldehyde showed the highest naringin conversion (73%). It was determined that the intermediate pore blocking model was the predominant fouling mechanism for the enzymatic immobilization. The EMR was applied for debittering of grapefruit juice, achieving a conversion of naringin below bitterness threshold and maintaining the antioxidant capacity of the juice. Furthermore, the biocatalytic activity of immobilized enzyme was retained at a high level at least during three consecutive reaction runs, with overnight storage at 4 °C after each run. Industrial relevanceThe potential of membrane technologies in the juice industries is widely recognized today. The development of EMR with naringinase activity is an attractive option for reducing bitterness that could replace current techniques, due to its high specificity and effectiveness, possibility of repeated and continuous use, and in order to retain the properties of juice as much as possible. The research therefore represents an advance in the application of biocatalytic membranes as technological alternative for juice debittering.

Dual-functional biocatalytic membrane containing laccase-embedded metal-organic frameworks for detection and degradation of phenolic pollutant

In this work, a metal–organic framework material, zeolitic imidazolate framework-90 (ZIF-90), was firstly used to encapsulate laccase (LAC) and to prepare ZIF-90/LAC biocomposites. Afterward, the composites were combined with bacterial cellulose (BC) and carboxylated multi-walled carbon nanotubes (c-MWCNTs) by a facile method to achieve a novel cellulose membrane with biocatalytic function, displaying excellent detection and degradation properties towards phenolic pollutant. Notably, the membrane was directly employed as a biosensor electrode, and it exhibited a linear response to catechol from 20 to 400 μM with a detection limit of 1.86 µM (S/N = 3), as well as satisfactory selectivity, reproducibility, and stability. In addition, the biocatalytic membrane showed higher degradation efficiency towards catechol than pure LAC, and the catechol degradation efficiency of the membrane generally ranged from 93.4% to 82.1% for five cycles. Moreover, the membrane was successfully applied in enzyme membrane reactor (EMR), achieving satisfactory results. The novel membrane harbors a broad application prospect in the fields of real-time monitor and treatment of phenolic wastewater.