Immobilization of carbonic anhydrase for CO2 capture and utilization

Behavior, mechanisms, and applications of low-concentration CO2 in energy media

This review explores the behavior of low-concentration CO2 (LCC) in various energy media, such as solid adsorbents, liquid absorbents, and catalytic surfaces. It delves into the mechanisms of diffusion, adsorption, and catalytic reactions, while analyzing the potential applications and challenges of these properties in technologies like air separation, compressed gas energy storage, and CO2 catalytic conversion. Given the current lack of comprehensive analyses, especially those encompassing multiscale studies of LCC behavior, this review aims to provide a theoretical foundation and data support for optimizing CO2 capture, storage, and conversion technologies, as well as guidance for the development and application of new materials. By summarizing recent advancements in LCC separation techniques (e.g., cryogenic air separation and direct air carbon capture) and catalytic conversion technologies (including thermal catalysis, electrochemical catalysis, photocatalysis, plasma catalysis, and biocatalysis), this review highlights their importance in achieving carbon neutrality. It also discusses the challenges and future directions of these technologies. The findings emphasize that advancing the efficient utilization of LCC not only enhances CO2 reduction and resource utilization efficiency, promoting the development of clean energy technologies, but also provides an economically and environmentally viable solution for addressing global climate change.

Overview on bacterial carbonic anhydrase genetic families

Bacterial carbonic anhydrases (BCAs, EC 4.2.1.1) are indispensable enzymes in microbial physiology because they facilitate the hydration of carbon dioxide (CO2) to bicarbonate ions (HCO3-) and protons (H+), which are crucial for various metabolic processes and cellular homeostasis. Their involvement spans from metabolic pathways, such as photosynthesis, respiration, to organic compounds production, which are pivotal for bacterial growth and survival. This chapter elucidates the diversity of BCA genetic families, categorized into four distinct classes (α, β, γ, and ι), which may reflect bacterial adaptation to environmental niches and their metabolic demands. The diversity of BCAs is essential not only for understanding their physiological roles but also for exploring their potential in biotechnology. Knowledge of their diversity enables researchers to develop innovative biocatalysts for industrial applications, including carbon capture technologies to convert CO2 emissions into valuable products. Additionally, BCAs are relevant to biomedical research and drug development because of their involvement in bacterial pathogenesis and microbial survival within the host. Understanding the diversity and function of BCAs can aid in designing targeted therapeutics that interfere with bacterial metabolism and potentially reduce the risk of infections.

Bacterial ι-CAs

Recent research has identified a novel class of carbonic anhydrases (CAs), designated ι-CA, predominantly found in marine diatoms, eukaryotic algae, cyanobacteria, bacteria, and archaea genomes. This class has garnered attention owing to its unique biochemical properties and evolutionary significance. Through bioinformatic analyses, LCIP63, a protein initially annotated with an unknown function, was identified as a potential ι-CA in the marine diatom Thalassiosira pseudonana. Subsequent biochemical characterization revealed that LCIP63 has CA activity and its preference for manganese ions over zinc, indicative of evolutionary adaptation to marine environments. Further exploration of bacterial ι-CAs, exemplified by Burkholderia territorii ι-CA (BteCAι), demonstrated catalytic efficiency and sensitivity to sulfonamide and inorganic anion inhibitors, the classical CA inhibitors (CAIs). The classification of ι-CAs into two variant types based on their sequences, distinguished by the COG4875 and COG4337 domains, marks a significant advancement in our understanding of these enzymes. Structural analyses of COG4337 ι-CAs from eukaryotic microalgae and cyanobacteria thereafter revealed a distinctive structural arrangement and a novel catalytic mechanism involving specific residues facilitating CO2 hydration in the absence of metal ion cofactors, deviating from canonical CA behavior. These findings underscore the biochemical diversity within the ι-CA class and highlight its potential as a target for novel antimicrobial agents. Overall, the elucidation of ι-CA properties and mechanisms advances our knowledge of carbon metabolism in diverse organisms and underscores the complexity of CA evolution and function.

Characterization of amyloid-like metal-amino acid assemblies with remarkable catalytic activity

While enzymes are potentially useful in various applications, their limited operational stability and production costs have led to an extensive search for stable catalytic agents that will retain the efficiency, specificity, and environmental-friendliness of natural enzymes. Despite extensive efforts, there is still an unmet need for improved enzyme mimics and novel concepts to discover and optimize such agents. Inspired by the catalytic activity of amyloids and the formation of amyloid-like assemblies by metabolites, our group pioneered the development of novel metabolite-metal co-assemblies (bio-nanozymes) that produce nanomaterials mimicking the catalytic function of common metalloenzymes that are being used for various technological applications. In addition to their notable activity, bio-nanozymes are remarkably safe as they are purely composed of amino acids and minerals that are harmless to the environment. The bio-nanozymes exhibit high efficiency and exceptional robustness, even under extreme conditions of temperature, pH, and salinity that are impractical for enzymes. Our group has recently also demonstrated the formation of ordered amino acid co-assemblies showing selective and preferential interactions comparable to the organization of residues in folded proteins. The identified bio-nanozymes can be used in various applications including environmental remediation, synthesis of new materials, and green energy.

Study of Preparation and Properties of Stereoregular Poly(cyclohexenylene carbonate)

Fixing carbon dioxide as a polymer material is an effective and environmentally beneficial approach for reducing the harm of CO₂ greenhouse gas. In this paper, carbon dioxide and cyclohexene oxide were used as co-monomers, and a chiral binuclear cobalt complex with a biphenyl linker was employed as the catalyst to successfully prepare a poly(cyclohexenylene carbonate) with high stereoregularity. The influence of catalyst structure, CO₂ pressure, and operating temperature on the copolymerization rate and polymer structure were systematically investigated. Optimal catalyst structure and operating conditions were determined, resulting in an excellent poly(cyclohexenylene carbonate) with a stereoregularity as high as 93.5%. Performance testing revealed that the polyester had a molecular weight of approximately 20 kg/mol, a glass transition temperature of 129.7 °C, an onset decomposition temperature of 290 °C, and a tensile strength of 42.8 MPa. These results demonstrate high thermal stability and mechanical strength, indicating the potential for expanding the applications of aliphatic polycarbonate materials.

Eight Up-Coming Biotech Tools to Combat Climate Crisis

Biotechnology has a high potential to substantially contribute to a low-carbon society. Several green processes are already well established, utilizing the unique capacity of living cells or their instruments. Beyond that, the authors believe that there are new biotechnological procedures in the pipeline which have the momentum to add to this ongoing change in our economy. Eight promising biotechnology tools were selected by the authors as potentially impactful game changers: (i) the Wood-Ljungdahl pathway, (ii) carbonic anhydrase, (iii) cutinase, (iv) methanogens, (v) electro-microbiology, (vi) hydrogenase, (vii) cellulosome and, (viii) nitrogenase. Some of them are fairly new and are explored predominantly in science labs. Others have been around for decades, however, with new scientific groundwork that may rigorously expand their roles. In the current paper, the authors summarize the latest state of research on these eight selected tools and the status of their practical implementation. We bring forward our arguments on why we consider these processes real game changers.

Carbonic Anhydrase Enhanced UV-Crosslinked PEG-DA/PEO Extruded Hydrogel Flexible Filaments and Durable Grids for CO2 Capture

In this study, poly (ethylene glycol) diacrylate/poly (ethylene oxide) (PEG-DA/PEO) interpenetrating polymer network hydrogels (IPNH) were extruded into 1D filaments and 2D grids. The suitability of this system for enzyme immobilization and CO₂ capture application was validated. IPNH chemical composition was verified spectroscopically using FTIR. The extruded filament had an average tensile strength of 6.5 MPa and elongation at break of 80%. IPNH filament can be twisted and bent and therefore is suitable for further processing using conventional textile fabrication methods. Initial activity recovery of the entrapped carbonic anhydrase (CA) calculated from esterase activity, showed a decrease with an increase in enzyme dose, while activity retention of high enzyme dose samples was over 87% after 150 days of repeated washing and testing. IPNH 2D grids that were assembled into spiral roll structured packings exhibited increased CO₂ capture efficiency with increasing enzyme dose. Long-term CO₂ capture performance of the CA immobilized IPNH structured packing was tested in a continuous solvent recirculation experiment for 1032 h, where 52% of the initial CO₂ capture performance and 34% of the enzyme contribution were retained. These results demonstrate the feasibility of using rapid UV-crosslinking to form enzyme-immobilized hydrogels by a geometrically-controllable extrusion process that uses analogous linear polymers for both viscosity enhancement and chain entanglement purposes, and achieves high activity retention and performance stability of the immobilized CA. Potential uses for this system extend to 3D printing inks and enzyme immobilization matrices for such diverse applications as biocatalytic reactors and biosensor fabrication.

Light and carbon: Synthetic biology toward new cyanobacteria-based living biomaterials

Cyanobacteria are ideal candidates to use in developing carbon neutral and carbon negative technologies; they are efficient photosynthesizers and amenable to genetic manipulation. Over the past two decades, researchers have demonstrated that cyanobacteria can make sustainable, useful biomaterials, many of which are engineered living materials. However, we are only beginning to see such technologies applied at an industrial scale. In this review, we explore the ways in which synthetic biology tools enable the development of cyanobacteria-based biomaterials. First we give an overview of the ecological and biogeochemical importance of cyanobacteria and the work that has been done using cyanobacteria to create biomaterials so far. This is followed by a discussion of commonly used cyanobacteria strains and synthetic biology tools that exist to engineer cyanobacteria. Then, three case studies-bioconcrete, biocomposites, and biophotovoltaics-are explored as potential applications of synthetic biology in cyanobacteria-based materials. Finally, challenges and future directions of cyanobacterial biomaterials are discussed.

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.

Microbial carbonic anhydrase mediated carbon capture, sequestration & utilization: A sustainable approach to delivering bio-renewables

In the recent scenario, anthropogenic interventions have alarmingly disrupted climatic conditions. The persistent change in the climate necessitates carbon neutrality. Efficient ways of carbon capture and sequestration could be employed for sustainable product generation. Carbonic anhydrase (CA) is an enzyme that reversibly catalyzes the conversion of carbon dioxide to bicarbonate ions, further utilized by cells for metabolic processes. Hence, utilizing CA from microbial sources for carbon sequestration and the corresponding delivery of bio-renewables could be the eco-friendly approach. Consequently, the microbial CA and amine-based carbon capture chemicals are synergistically applied to enhance carbon capture efficiency and eventual utilization. This review comprehends recent developments coupled with engineering techniques, especially in microbial CA, to create integrated systems for CO₂ sequestration. It envisages developing sustainable approaches towards mitigating environmental CO₂ from industries and fossil fuels to generate bio-renewables and other value-added chemicals.