Approaches in biotechnological applications of natural polymers

Natural polymers, such as gums and mucilage, are biocompatible, cheap, easily available and non-toxic materials of native origin. These polymers are increasingly preferred over synthetic materials for industrial applications due to their intrinsic properties, as well as they are considered alternative sources of raw materials since they present characteristics of sustainability, biodegradability and biosafety. As definition, gums and mucilages are polysaccharides or complex carbohydrates consisting of one or more monosaccharides or their derivatives linked in bewildering variety of linkages and structures. Natural gums are considered polysaccharides naturally occurring in varieties of plant seeds and exudates, tree or shrub exudates, seaweed extracts, fungi, bacteria, and animal sources. Water-soluble gums, also known as hydrocolloids, are considered exudates and are pathological products; therefore, they do not form a part of cell wall. On the other hand, mucilages are part of cell and physiological products. It is important to highlight that gums represent the largest amounts of polymer materials derived from plants. Gums have enormously large and broad applications in both food and non-food industries, being commonly used as thickening, binding, emulsifying, suspending, stabilizing agents and matrices for drug release in pharmaceutical and cosmetic industries. In the food industry, their gelling properties and the ability to mold edible films and coatings are extensively studied. The use of gums depends on the intrinsic properties that they provide, often at costs below those of synthetic polymers. For upgrading the value of gums, they are being processed into various forms, including the most recent nanomaterials, for various biotechnological applications. Thus, the main natural polymers including galactomannans, cellulose, chitin, agar, carrageenan, alginate, cashew gum, pectin and starch, in addition to the current researches about them are reviewed in this article.. }To the Conselho Nacional de Desenvolvimento Cientfíico e Tecnológico (CNPq) for fellowships (LCBBC and MGCC) and the Coordenação de Aperfeiçoamento de Pessoal de Nvíel Superior (CAPES) (PBSA). This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, the Project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462) and COMPETE 2020 (POCI-01-0145-FEDER-006684) (JAT)

Development and application of poly(ionic liquid) composite membranes with immobilized carbonic anhydrase for CO2 absorption in gas-liquid membrane contactors

In the current climate crisis, CO2 capture and utilization appears to be essential in achieving the climate targets. Among the alternatives, CO2 can be utilized as sodium bicarbonate salts, NaHCO3. This product is obtained by absorbing CO2 into Na2CO3 aqueous solutions, which are kinetically limited solvents. Nevertheless, adding promoters such as the biocatalyst carbonic anhydrase can enhance their absorption rate. The enzyme is exceptionally active and can work in mild conditions. However, enzymes are homogenous catalysts with limited stability. This issue can be addressed through enzyme immobilization on a support. Thus, gas-liquid membrane contactors with carbonic anhydrase immobilized on the membrane surface are a promising technology for accelerating the absorption of CO2. This work's novelty comes from employing ionic liquid-derived materials, mainly polymerized ionic liquids or poly(ionic liquid)s, a class of tunable CO2-philic polymers, to anchor the enzyme to the membrane surface. Different immobilization approaches were compared: entrapment, physical adsorption, and covalent bonding. The most promising results were obtained with the physical adsorption of carbonic anhydrase on hydrophilic poly(ionic liquid)s. Overall, the materials developed during this Ph.D. thesis displayed interesting performance for their application in CO2 capture and utilization.(FSA - Sciences de l'ingénieur) -- UCL, 202

Application of enzyme integrated supported ionic liquid membranes and poly(ionic liquid)-free ionic liquid composite membranes in CO2-N2 separation

Global warming is a major problem of our current society. Since our energy demand is continuously increasing it is still expected to rely on fossil fuel supply in the following years [1]. That is why much effort has been dedicated to find industrially feasible solutions to recover the CO2 present in flue gases. But typical conditions of flue gases (high temperature and low CO2 concentration) makes more difficult to recover CO2 [2]. Aiming to provide technical solutions several researches have investigated the application in gas permeation of supported ionic liquid membranes (SILM) and poly(ionic liquid) membranes (PIL) to separate CO2-N2 mixtures [3][4]. N2 is the major component in flue gases. Promising results in regards to permeability and selectivity have been obtained [5]. In order to farther improve the separation performance, some research groups carried out gas permeation tests in which they introduced carbonic anhydrase enzyme into SILMs [6][7][8]. This enzyme catalyzes the hydration reaction of CO2. They showed that the separation is improved due to the facilitated transport provided by the presence of the enzyme. However, these authors only tested only one type of ionic liquid (IL) and only one type of supporting membrane. Much can be still improved by selecting more appropriated IL-support material combinations [9]. In addition, gas permeation requires pressurization of the feed in order to achieve a sufficiently high driving force [5]. Furthermore, CO2 is generally recovered as CO2 gas that would be stored underground. Here, a novel approach in which membrane contactors will be combined with SILM and PIL-IL composite membranes both integrating enzymes will be addressed (see Figure 1). In both cases the enzyme will be dissolved in the IL. In the membrane contactor a receiving liquid phase will have two purposes: recover CO2 in form of a valuable product (produced by the enzyme) and to provide other substrates required for the enzymatic reaction that takes place inside of the membrane. Two enzymes will be tested: carbonic anhydrase and modified RuBisCO. Performing absorption experiments the influence of several parameters (temperature, IL type, enzyme concentration and CO2 partial pressure) in the mass transfer will analyzed (see Figure 2). Results will be modelled using the so called Solution-diffusion model but other models that take into account the reaction inside of the membrane will be applied as well. Finally, the study of membrane stability and economic viability of this solution will be also important topics. References [1] IEA. (2016). OECD/IEA, Paris, France. [2] Merkel, T. et al. (2010). J Memb Sci., 359(1-2), 126-139. [3] Kim, D. H. et al. (2011). J Memb Sci., 372(1-2), 346-354. [4] Li, P. et al. (2012). Green Chem., 14(4), 1052-1063. [5] Luis, P., & Van der Bruggen, B. (2013). Greenhouse Gases: Science and Technology, 3(5), 318-337. [6] Neves, L. A., (2012). Sep. Purif. Technol., 97, 34-41. [7] Bednár, A., (2016). Chem Eng J., 303, 621-626. [8] Abdelrahim, M. Y. M., (2017). J Memb Sci., 528, 225-230. [9] Ramdin, M., (2012). Ind. Eng. Chem. Res., 51(24), 8149-8177

Immobilization of carbonic anhydrase for CO2 capture and its industrial implementation: A review

Minimal cost per ton of captured CO2 and associated environmental impacts are considerable barriers for the industrial implementation of post-combustion CO2 capture. Aqueous solvents promoted with the enzyme carbonic anhydrase are a promising alternative to replace energy intensive and environmentally unfriendly aminebased solutions, which are currently benchmark solvents in CO2 absorption. However, using free enzyme in solution requires significant amounts of enzyme in addition to its possible denaturalization. Enzyme immobilization appears as a rational approach to develop a novel CO2 capture system using aqueous solvents. In the recent literature, efforts are focused on the development and characterization of different carriers and immobilization strategies to achieve good activity and stability compared to free enzyme in solution. In the laboratory and the industry, immobilized carbonic anhydrase have been already tested in a variety of configurations including packed columns, gas-liquid membrane contactors, dynamic devices and selective membranes. This article reviews the developments, opportunities and limitations found at laboratory scale as well as in the industry, and brings them together in order to identify the key challenges and perspectives in the industrial implementation of immobilized carbonic anhydrase for CO2 capture

Biocatalytic composite membranes for CO2 capture

Nature has developed very active and specific catalysts that are critical for living organisms’ existence. The application of some of such biocatalysts in CO2 capture and utilization has recently attracted large interest from the research community and the industry [1,2]. For example, they have been applied to CO2 absorption aiming to reduce the liquid side mass transfer resistance. This resistance is dominating the overall mass transfer and it can be reduced by catalyzing the slow CO2 hydration reaction. Besides, they have also been incorporated in selective membranes. These membranes usually displayed improved permeability and selectivity due to the facilitated transport mechanism [2]. In addition, these biocatalysts are usually immobilized in/on a carrier to protect them from the harsh conditions in CO2 capture and ensure long-term stability. Depending on the immobilization method, the immobilization results in different degrees of stabilization and activity loss. We report here the fabrication and characterization of novel composite membranes with immobilized biocatalyst for CO2 bioconversion. These membranes were prepared by a novel method that ensured a good and straightforward biocatalyst immobilization. The membranes were structurally characterized by SEM while their activity in different conditions was evaluated using p-NPA hydrolysis. In addition, to demonstrate their applicability, the biocatalytic composite membranes were tested in a gas absorption set-up showing an increase in the overall mass transfer coefficient with respect to the pristine support. These membranes could also be interesting for other applications as the combination of a selective barrier and the biocatalyst leads to process intensification (reaction + separation in the same device). [1] P. Luis, V. Sang Sefidi, M. Sparenberg, M. Garcia Alvarez. (2021), continuous process and system for the production of sodium bicarbonate crystals, 20211693.5-1108, universite catholique de louvain. (Patent) [2] Molina-Fernández, C., & Luis, P. (2021). Immobilization of carbonic anhydrase for CO2 capture and its industrial implementation: A review. Journal of CO2 Utilization, 47, 101475

Selection and characterization of ionic liquids for the potential recovery of dimethyl carbonate from methanol/dimethyl carbonate by pervaporation

The use of pervaporation to separate organic-organic mixtures has attracted increasing interest in the research community, as the technology exhibits great potential (considering its low energy consumption) [1]. For example, valorisation of CO2 as a platform molecule to produce dimethyl carbonate (DMC) is of utmost interest, but it involves the reaction of CO2 with methanol (MeOH) to produce DMC [2-4]. This reaction is limited by the equilibrium and an azeotrope between dimethyl carbonate and methanol is also present. Thus, the low yield and high separation costs using conventional technology make this process uninteresting for a real application. In the past few years, ionic liquids (ILs) have received more and more attention as catalysts for the synthesis of DMC from CO2 and MeOH, considering their wide liquid range and excellent thermal and chemical stability[5]. Besides being used as catalysts, ILs have also showed potential in pervaporation separation. In order to screen out ILs suitable for extracting dimethyl carbonate (DMC) from a mixture of DMC/methanol (MeOH), three kinds of ionic liquids (ILs) 1-Octyl-3-methylimidazolium bromide [1O3MIm][Br], 1-Octyl-1,4-diazabicyclo[2.2.2]octanium bromide [ODABCO][Br], and 1-Octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [1O3MIm][Br] were successfully synthesized and their chemical structures were confirmed by NMR. These three ILs and one commercial IL Tetrabutylammonium bromide [TBA][Br] were further characterised by DSC/TGA and processed into supported ionic liquid membranes (SILMs). SILMs shows a decrease in MeOH permeance almost without compromising DMC permeance and higher ideal DMC/MeOH selectivity at low temperature compared to PAN

Biopolymers as a promising platform for biocatalyst immobilization in novel gas-liquid membrane contactor for carbon capture

Post-combustion carbon capture using membrane-based processes represents one of the potential technologies to mitigate the release of the greenhouse gases to the atmospheric. Gas-liquid membrane contactor (GLMC) utilizing porous hydrophobic membrane as a physical barrier to separate gaseous feed and liquid absorbent streams has a clear major advantage, i.e., excellent selectivity and lower energy requirement, over pressure-driven membrane gas separation at very low CO2 concentration. However, conventional GLMC suffers several major drawbacks, such as membrane wetting, toxic amine solvents and energy-intensive CO2 desorption process. Recently, more benign solvents, such as sodium carbonate (Na2CO3), have been used in place of amines to perform CO2 capture in GLMC. The slower absorption kinetics of these solvents, unfortunately, are not able to compete with the performance of conventional amines. Incorporating biocatalysts that promote CO2 hydration could accelerate the CO2 capture rate of these solvents. In this work, we prepared novel biocatalytic membranes using biopolymer coating as an immobilization platform. The coating concentration, membrane coating method, immobilization parameters and process conditions were varied. The membrane was evaluated in an open-loop gaseous feed and a circulated liquid absorbent solution. Our work demonstrated that the membrane with the immobilized biocatalyst had a significant increase in the overall mass transfer coefficient: an increase of ~650% compared to pristine membranes. The membrane was also tested several times and showed no sign of performance deterioration. In conclusion, our results clearly highlighted the impressive performance of novel biopolymer-coated membranes as a platform for biocatalysts immobilization in CO2 capture process

Carbonic anhydrase immobilization in poly(ionic liquid) based materials for application in CO2 separation by membranes

Carbonic anhydrase (CA) has been extensively studied as CO2 hydration kinetics enhancer in CO2 absorption. The main driver is that the hydration reaction is the rate limiting step when applying aqueous benign solvents to capture CO2. To protect the enzyme from the harsh conditions in the stripper, CA is usually immobilized. However, depending on the immobilization method, this procedure can lead to reduction of enzyme activity or increase of mass transfer limitations. Room temperature ionic liquids (ILs) have been proven as potential solvents in biochemical reactions, increasing in many cases the enzyme activity and stability with respect to organic solvents. Furthermore, polymerized ILs (PIL) present high CO2 solubility. Therefore, there has been numerous studies focused on the application of PIL to gas permeation. However, research on enzyme immobilization in PIL based materials is limited. The present study focus on the elaboration, characterization and testing of CA immobilized in poly(ionic liquid) based materials for the development of membranes. Different materials are studied such as hydrophobic and hydrophilic PILs with different cross-linker amounts. They are characterized by delta pH method, pPNA hydrolysis, Bradford assay, FT-IR, SEM, DSC etc. Concerning enzyme activity, changes on Toptimum and pHoptimum are addressed. Additionally, leaching and stability are analysed. Changes in enzyme activity/stability are discussed in terms of interactions with the PIL

Thin film enzyme - poly(ionic liquid) – free ionic liquid composite membranes for enhanced CO2 absorption with carbonate aqueous solutions

Carbonic anhydrase (CA) has been extensively studied in literature as CO2 hydration kinetics enhancer in CO2 absorption since the hydration reaction is the limiting step when using aqueous benign solvents. To protect the enzyme from the harsh conditions in the stripper, CA is usually immobilized. However, depending on the immobilization method, this procedure can lead to the reduction of enzyme activity or the increase of mass transfer limitations. Room temperature ionic liquids (ILs) have been proven as potential solvents in biochemical reactions, increasing in many cases the enzyme activity and stability. Furthermore, polymerized ILs (PIL) present high CO2 solubility. The present study focus on the elaboration, characterization and testing of CA integrated poly(ionic liquid) – free ionic liquid composite membranes in CO2 absorption using aqueous benign solvents. To reduce diffusional mass transfer limitations, thin film PIL-IL membranes with high free IL content were prepared by bulk free radical polymerization on top of a porous PVDF support. The enzyme was dissolved in the free IL before polymerization ensuring immobilization by physical entrapment inside of the cross-linked polymeric matrix. The PIL studied was poly(1-Vinyl-3-hexylimidazolium bis(trifluoromethylsulfonyl)imide) while different amounts (0, 30 and 75 %w) and types of free ILs (1-butyl/hexyl/octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and biocompatible choline based ILs) were analysed to see the effect on enzyme activity/stability and separation performance. Furthermore, the effect of CA concentration was also addressed. Experiments were performed in a membrane contactor set-up using water and potassium carbonate solutions as absorbent. The presence of CA should produce a significant increase of permeability compared to the case without CA. It is also expected to see a trade-off between enzyme activity/stability and diffusion of CO2 in the membrane when free ILs of different hydrophobic character are compared. Finally, this study aims to expand the use of enzymes in CO2 absorption by placing them in the broader context of membrane contactors

Evaluation of task-specific ionic liquids applied in pervaporation membranes: Experimental and COSMO-RS studies

The production of dimethyl carbonate (DMC) from CO2 and methanol (MeOH) is an attractive route for CO2 capture and utilization. In this process, the separation of DMC from the reaction medium is critical to maximize the conversion of CO2. However, DMC and MeOH form an azeotropic mixture that is difficult to separate. This work investigates the possibility of using task-specific ionic liquids (TSILs) in the form of supported ionic liquid membranes (SILMs) to separate and purify DMC by using pervaporation. Two tertiary amine ILs, i.e., 1-octyl-3-methylimidazolium bromide ([Omim][Br]) and 1-octyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([Omim][NTf2]), and one cyclic quaternary ionic liquid, i.e., 1-octyl-1,4-diazabicyclo[2.2.2]octanium bromide ([ODABCO][Br]), were prepared. The structure and purity of the synthesized ILs were confirmed by NMR and FTIR, and the as-synthesized ILs along with one commercial quaternary ammonium IL, tetrabutylammonium bromide ([TBA][Br]), were further characterized using TGA/DSC. SEM-EDX, tensile tests and stability tests were also performed to characterize the SILMs. During the pervaporation experiments, the SILMs showed an initial decrease in DMC and MeOH permeance over time, followed by a gradual stabilization, with a relatively stable DMC/MeOH selectivity as pure liquids. In addition, an increase in temperature is shown to have negative effect on DMC and MeOH permeance because sorption, which is an exothermic process, governed the transport of molecules across the membrane. The studied SILMs exhibited higher selectivity at low temperatures, especially at 30 °C. Furthermore, the COSMO-RS model provided insights of the effect of IL structures on the separation of DMC from MeOH at molecular level