Trends, application and future prospectives of microbial carbonic anhydrase mediated carbonation process for CCUS

Microbial transformation of soil organic matter under varying agricultural management systems in Ukraine

Introduction

This paper presents comparative studies on the content and structure of organic matter (OM) and the activity of microbiological cellulose destruction in three types of Ukrainian soils intensively used in agricultural production.

Methods

The highest content of humus in the arable layer (4.9%), OM (410 t ha-1), and total carbon (30.9 mg C g-1 soil) was determined in chernic phaeozems, which is 2.2-2.5 times higher than in albic retisols. The soil of natural ecosystems is characterised by a high content of microbial carbon (Cmic) in the carbon fraction of organic soil compounds.

Results and discussion

In arable soils, the content and reserves of humus and soil organic matter (SOM) have decreased by an average of 1.5-2 times. The most considerable loss of humus reserves in the soil profile was identified in albic retisols (1.96-1.44 times) and the smallest in chernic phaeozems (1.27-1.81 times). During the long-term systematic application of mineral fertilisers, the Corg content decreased by 8-21% in chernic phaeozems, 12-33% in greyzemic phaeozems, and 6-38% in albic retisols. A significant difference of 2.1-8.0 times was determined regarding the number of aerobic cellulolytic microorganisms and 1.3-3.3 times in the potential cellulolytic activity of the studied soils. The high number of cellulose-destroying microorganisms is characteristic of chernic phaeozems with a high content of OM in the soil; the advantage over other types of studied soils was 1.4 times and 7.8 times for greyzemic phaeozems and albic retisols, respectively. Among the studied soil types, high values of CO2 emissions were identified in chernic phaeozems. Intensive agricultural practices in Ukrainian soils have significantly altered the content and composition of organic matter, leading to reduced humus and soil organic matter reserves. The study also underscores the importance of considering the abundance of cellulose-destroying microorganisms and their potential activity in assessing soil health and sustainability.

Urban mining of municipal solid waste incineration (MSWI) residues with emphasis on bioleaching technologies: a critical review

Metals are essential in our daily lives and have a finite supply, being simultaneously contaminants of concern. The current carbon emissions and environmental impact of mining are untenable. We need to reclaim metals sustainably from secondary resources, like waste. Biotechnology can be applied in metal recovery from waste streams like fly ashes and bottom ashes of municipal solid waste incineration (MSWI). They represent substantial substance flows, with roughly 46 million tons of MSWI ashes produced annually globally, equivalent in elemental richness to low-grade ores for metal recovery. Next-generation methods for resource recovery, as in particular bioleaching, give the opportunity to recover critical materials and metals, appropriately purified for noble applications, in waste treatment chains inspired by circular economy thinking. In this critical review, we can identify three main lines of discussion: (1) MSWI material characterization and related environmental issues; (2) currently available processes for recycling and metal recovery; and (3) microbially assisted processes for potential recycling and metal recovery. Research trends are chiefly oriented to the potential exploitation of bioprocesses in the industry. Biotechnology for resource recovery shows increasing effectiveness especially downstream the production chains, i.e., in the waste management sector. Therefore, this critical discussion will help assessing the industrial potential of biotechnology for urban mining of municipal, post-combustion waste.

Use of bacterial binder in repair mortar for micro-crack remediation

Micro-cracks are one of the types of stone deterioration which can propagate and lead to surface detachments and larger cracks in the long run. The present study developed a sustainable and environmentally friendly infill material-biological mortar (BM), as an alternative to conventional approaches. Using a biomineralization approach, this BM was explicitly designed for healing micro-cracks (less than 2 mm) in historic travertines. To this end, the mortar was prepared using a calcifying Bacillus sp. isolated from thermal spring water resources in Pamukkale Travertines (Denizli), stone powder gathered from travertine quarries in the vicinity, and a triggering solution specifically designed to set off calcium carbonate precipitation reaction. After setup, BM was applied to micro-cracks of artificially aged test stones for testing. Scanning electron microscopy revealed calcium carbonate-coated Bacillus sp. bodies in the BM matrix, optical microscopy showed secondary calcite minerals throughout the BM applied micro-cracks, and stereomicroscopy and nanoindentation analyses demonstrated bonding of BM with stone due to microbial calcification activities. Furthermore, BM and original material contact showed a continuous and coherent structure in all samples. Within this context, BM could be considered a promising and alternative approach for the remediation of micro-cracks of historic stones. KEY POINTS: A binder was produced by the MICP of Bacillus sp. Pamukkale. Physical, mineralogical, and nanomechanical characterization demonstrated microbial calcite precipitates in BM. A significant bond was determined between the grains and matrix of BM due to Bacillus sp. calcite production activities.

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.

Evidencing the role of carbonic anhydrase in the formation of carbonate minerals by bacterial strains isolated from extreme environments in Qatar

Calcium carbonate, one of the most abundant minerals in the geological records is considered as primary source of the carbon reservoir. The role of microorganisms in the biotic precipitation of calcium carbonate has been extensively investigated, especially at extreme life conditions. In Qatar, Sabkhas which are microbial ecosystems housing biomineralizing bacteria, have been carefully studied as unique sites of microbial dolomite formation. Dolomite (CaMg(CO₃)₂ is an important carbonate mineral forming oil reservoir rocks; however, dolomite is rarely formed in modern environments. The enzyme carbonic anhydrase is present in many living organisms, performs interconversion between CO₂ and the bicarbonate ion. Thus, carbonic anhydrase is expected to accelerate both carbonate rock dissolution and CO₂ uptake at the same time, serving as carbonite source to carbonites-forming bacteria. This study gathered cross-linked data on the potential role of the carbonic anhydrase excreted by mineral-forming bacteria, isolated from two different extreme environments in Qatar. Dohat Faishakh Sabkha, is a hypersaline coastal Sabkha, from where various strains of the bacterium Virgibacillus were isolated. Virgibacillus can -not only-mediate carbonate mineral formation, but also contributes to magnesium incorporation into the carbonate minerals, leading to the formation of high magnesium calcite. The latter is considered as precursor for dolomite formation. In addition, bacterial strains isolated from marine sediments, surrounding coral reef in Qatar sea, would provide additional knowledge on the role of carbonic anhydrase in mineral formation. Here, the quantification of the two mostly described activities of carbonic anhydrase; esterase and hydration reactions were performed. Mineral-forming strains were shown to exhibit high activities as opposed to the non-forming minerals, which confirms the relation between the presence of active carbonic anhydrase combined with elevated metabolic activity and the biomineralizing potential of the bacterial strains. The highest specific intracellular carbonic anhydrase activity; as both esterase and hydration (i.e., 66 ± 3 and 583000 ± 39000 WAU/10⁸ cells respectively), was evidenced in mineral-forming strains as opposed to non-mineral forming strains (i.e., 6 ±. 0.5 and 1223 ± 61 WAU/10⁸cells) respectively. These findings would contribute to the understanding of the mechanism of microbially mediated carbonate precipitation. This role may be both in capturing CO₂ as source of carbonate, and partial solubilization of the formed minerals allowing incorporation of Mg instead of calcium, before catalyzing again the formation of more deposition of carbonates.

Utilization of Bio-Mineral Carbonation for Enhancing CO2 Sequestration and Mechanical Properties in Cementitious Materials

Microorganisms can perform mineral carbonation in various metabolic pathways, and this process can be utilized in the field of construction materials. The present study investigated the role of bio-mediated mineral carbonation in carbon sequestration performance and mechanical properties of cementitious materials. Bacterial-mediated ureolysis and CO2 hydration metabolism were selected as the main mechanisms for the mineral carbonation, and a microorganism, generating both urease and carbonic anhydrase, was incorporated into cementitious materials in the form of a bacterial culture solution. Four paste specimens were cured in water or carbonation conditions for 28 days, and a compressive strength test and a mercury intrusion porosimetry analysis were performed to investigate the changes in mechanical properties and microstructures. The obtained results showed that the pore size of the specimens incorporating bacteria was reduced by the precipitation of CaCO3 through the mineral carbonation process, thereby improving the mechanical properties of the paste specimens, regardless of the curing conditions. In addition, in the case of the paste specimens cured in carbonation conditions, more amorphous CaCO3 was observed and a larger amount of CaCO3 in the specimens incorporating the bacteria was measured than in the specimens without bacteria. This is attributed to promotion of the inflow and diffusion of CO2 via mineral carbonation through bacterial CO2 hydration metabolism.

Amine- and Amino Acid-Based Compounds as Carbonic Anhydrase Activators

After being rather neglected as a research field in the past, carbonic anhydrase activators (CAAs) were undoubtedly demonstrated to be useful in diverse pharmaceutical and industrial applications. They also improved the knowledge of the requirements to selectively interact with a CA isoform over the others and confirmed the catalytic mechanism of this class of compounds. Amino acid and amine derivatives were the most explored in in vitro, in vivo and crystallographic studies as CAAs. Most of them were able to activate human or non-human CA isoforms in the nanomolar range, being proposed as therapeutic and industrial tools. Some isoforms are better activated by amino acids than amines derivatives and the stereochemistry may exert a role. Finally, non-human CAs have been very recently tested for activation studies, paving the way to innovative industrial and environmental applications.

Circular Carbon Economy (CCE): A Way to Invest CO2 and Protect the Environment, a Review

Increased levels of carbon dioxide have revolutionised the Earth; higher temperatures, melting icecaps, and flooding are now more prevalent. Fortunately, renewable energy mitigates this problem by making up 20% of human energy needs. However, from a “green environment” perspective, can carbon dioxide emissions in the atmosphere be reduced and eliminated? The carbon economic circle is an ideal solution to this problem, as it enables us to store, use, and remove carbon dioxide. This research introduces the circular carbon economy (CCE) and addresses its economic importance. Additionally, the paper discusses carbon capture and storage (CCS), and the utilisation of CO2. Furthermore, it explains current technologies and their future applications on environmental impact, CO2 capture, utilisation, and storage (CCUS). Various opinions on the best way to achieve zero carbon emissions and on CO2 applications and their economic impact are also discussed. The circular carbon economy can be achieved through a highly transparent global administration that is supportive of advanced technologies that contribute to the efficient utilisation of energy sources. This global administration must also provide facilities to modernise and develop factories and power stations, based on emission-reducing technologies. Monitoring emissions in countries through a global monitoring network system, based on actual field measurements, linked to a worldwide database allows all stakeholders to track the change in greenhouse gas emissions. The process of sequestering carbon dioxide in the ocean is affected by the support for technologies and industries that adopt the principle of carbon recycling in order to maintain the balance. This includes supporting initiatives that contribute to increasing vegetation cover and preserving oceans from pollutants, especially chemicals and radioactive pollutants, which will undoubtedly affect the process of sequestering carbon dioxide in the oceans, and this will contribute significantly to maintaining carbon dioxide at acceptable levels.

Kinetic study of catalytic CO2 hydration by metal-substituted biomimetic carbonic anhydrase model complexes

The rapid rise of the CO₂ level in the atmosphere has spurred the development of CO₂ capture methods such as the use of biomimetic complexes that mimic carbonic anhydrase. In this study, model complexes with tris(2-pyridylmethyl)amine (TPA) were synthesized using various transition metals (Zn²⁺, Cu²⁺ and Ni²⁺) to control the intrinsic proton-donating ability. The pK_a of the water coordinated to the metal, which indicates its proton-donating ability, was determined by potentiometric pH titration and found to increase in the order [(TPA)Cu(OH₂)]²⁺ < [(TPA)Ni(OH₂)]²⁺ < [(TPA)Zn(OH₂)]²⁺. The effect of pK_a on the CO₂ hydration rate was investigated by stopped-flow spectrophotometry. Because the water ligand in [(TPA)Zn(OH₂)]²⁺ had the highest pK_a, it would be more difficult to deprotonate it than those coordinated to Cu²⁺ and Ni²⁺. It was, therefore, expected that the complex would have the slowest rate for the reaction of the deprotonated water with CO₂ to form bicarbonate. However, it was confirmed that [(TPA)Zn(OH₂)]²⁺ had the fastest CO₂ hydration rate because the substitution of bicarbonate with water (bicarbonate release) occurred easily.

Characterization of marine bacterial carbonic anhydrase and their CO2 sequestration abilities based on a soil microcosm

The novel technology of biological carbon sequestration using microbial enzymes have numerous advantages over conventional sequestration strategies. In the present study, extracellular carbonic anhydrase (CA) producing bacteria were isolated from water samples in the Arabian Sea, India. A potential isolate, Bacillus safensis isolate AS-75 was identified based on 16S rDNA sequence analysis. The culture conditions suitable for CA production were 32 °C incubation temperature with 4% NaCl and 10 mM Zn supplementation. Experimental optimization of culture conditions enhanced enzyme activity to 265 U mL^-1. CA specific gene was characterized and based on the analysis, the CA of B. safensis isolate AS-75 was a leucine (11.3%) with α-helices as the dominant component in its secondary structure. Based on soil microcosm studies, CA could sequester CO₂ by 95.4% ± 0.11% in sterilized soil with enzyme microcosm. Hence, the application of enzyme was found to be more effective in removing CO₂.

Accelerated CO₂ Hydration with Thermostable Sulfurihydrogenibium azorense Carbonic Anhydrase-Chitin Binding Domain Fusion Protein Immobilised on Chitin Support

Carbonic anhydrases (CAs) represent a group of enzymes that catalyse important reactions of carbon dioxide hydration and dehydration, a reaction crucial to many biological processes and environmental biotechnology. In this study we successfully constructed a thermostable fusion enzyme composed of the Sulfurihydrogenibium azorense carbonic anhydrase (Saz_CA), the fastest CA discovered to date, and the chitin binding domain (ChBD) of chitinase from Bacillus circulans. Introduction of ChBD to the Saz_CA had no major impact on the effect of ions or inhibitors on the enzymatic activity. The fusion protein exhibited no negative effects up to 60 °C, whilst the fusion partner appears to protect the enzyme from negative effects of magnesium. The prepared biocatalyst appears to be thermally activated at 60 °C and could be partially purified with heat treatment. Immobilisation attempts on different kinds of chitin-based support results have shown that the fusion enzyme preferentially binds to a cheap, untreated chitin with a large crystallinity index over more processed forms of chitin. It suggests significant potential economic benefits for large-scale deployment of immobilised CA technologies such as CO₂ utilisation or mineralisation.