Characterization of carbonic anhydrase from diversified genus for biomimetic carbon-dioxide sequestration

Purification and biochemical characterization of a novel carbonic anhydrase II from erythrocytes of camel (Camelusdromedarius)

A novel carbonic anhydrase II (CA II) from erythrocytes of camel (Camelus dromedarius) was purified to homogeneity using affinity chromatography and biochemically characterized. Specific activity of 140.88 U/mg was obtained with 745.17-fold purification and 25.37% yield. The enzyme was a monomer with a lower molecular weight (25 kDa) and lower Zn content (0.50 mol of Zn per mol of protein). The enzyme showed higher optimum temperature (70 °C) and pH (pH 9.0), moreover, it was stable at higher temperatures and strongly alkaline pH as judged by thermodynamic parameters (Ea, kd, Ed, t1/2, D-value, Z-value, ΔH, ΔG and ΔS). The enzyme was inhibited by cations (Al3+, Ca2+, Cd2+, Co2+, Cr3+, Cu2+, Fe3+, Ni2+, Mg2+ and Zn2+) as well as by anions (Br‾, CH3COO‾, ClO4‾, CN‾, F‾, HCO3‾, I‾, N3‾, NO3‾ and SCN‾), some anions (C6H5O73-, CO32-, SeO3‾ and SO42-) does not affect enzyme activity. Effect of various chemicals on enzyme activity was also investigated. Km, Vmax, kcat and kcat/Km values for 4-NPA were found to be 1.74 mM, 0.0093 U/mL, 0,0039 s-1 and 0,0023 s-1 mM-1, respectively. With these interesting biochemical properties, camel CA II represents promising candidate for harsh industrial applications, in particular, for a successful biomimetic CO2 sequestration process.

Biosequestration of carbon dioxide using carbonic anhydrase from novel Streptomyces kunmingensis

The increase in the atmospheric concentrations of carbon dioxide due to anthropogenic interventions has led to several undesirable consequences, notably global warming and related changes. Avoidance of and/or removal of carbon dioxide will result in the reduction of global warming. Biosequestration of carbon by using carbonic anhydrase (CA) as biocatalyst is one of most effective approaches. In the present study, actinobacterial cultures isolated from bamboo (Bambusa vulgaris) rhizosphere were screened for the production of carbonic anhydrase enzyme. The strain BS19 which showed promising CA production was selected as the potential strain. Strain BS19 was identified as Streptomyces kunmingensis based on the phenotypic and molecular characteristics. In submerged fermentation, strain BS19 produced 214.21 IU/ml of CA enzyme. The molecular mass of the CA was determined as 45 ± 2 kDa. The production of CA was found to be optimal at pH 7.0 and at temperature of 28 °C. The full length periplasmic CA gene was successfully amplified from S. kunmingensis BS19. Biomimetic sequestration of carbon was detected and quantified through CaCO₃ precipitation method. Further, the CA of BS 19 was successfully used to mineralize CO₂ present in motorbike exhaust, which has a similar composition to that of flue gas. The well-defined rhombohedral calcite crystals formed in the mineral carbonation reaction was observed through SEM analysis. The findings of this study clearly indicated that Streptomyces kunmingensis BS19 isolated from bamboo rhizosphere is a promising candidate for the production of carbonic anhydrase which deserves the potential for CO₂ sequestration.

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

Growing industrialization and the desire for a better economy in countries has accelerated the emission of greenhouse gases (GHGs), by more than the buffering capacity of the earth's atmosphere. Among the various GHGs, carbon dioxide occupies the first position in the anthroposphere and has detrimental effects on the ecosystem. For decarbonization, several non-biological methods of carbon capture, utilization and storage (CCUS) have been in use for the past few decades, but they are suffering from narrow applicability. Recently, CO₂ emission and its disposal related problems have encouraged the implementation of bioprocessing to achieve a zero waste economy for a sustainable environment. Microbial carbonic anhydrase (CA) catalyses reversible CO₂ hydration and forms metal carbonates that mimic the natural phenomenon of weathering/carbonation and is gaining merit for CCUS. Thus, the diversity and specificity of CAs from different micro-organisms could be explored for CCUS. In the literature, more than 50 different microbial CAs have been explored for mineral carbonation. Further, microbial CAs can be engineered for the mineral carbonation process to develop new technology. CA driven carbonation is encouraging due to its large storage capacity and favourable chemistry, allowing site-specific sequestration and reusable product formation for other industries. Moreover, carbonation based CCUS holds five-fold more sequestration capacity over the next 100 years. Thus, it is an eco-friendly, feasible, viable option and believed to be the impending technology for CCUS. Here, we attempt to examine the distribution of various types of microbial CAs with their potential applications and future direction for carbon capture. Although there are few key challenges in bio-based technology, they need to be addressed in order to commercialize the technology.

Expression and characterization of a codon-optimized alkaline-stable carbonic anhydrase from Aliivibrio salmonicida for CO2 sequestration applications

The CO₂ mineralization process, accelerated by carbonic anhydrase (CA) was proposed for the efficient capture and storage of CO₂, the accumulation of which in the atmosphere is the main cause of global warming. Here, we characterize a highly stable form of the cloned CA from the Gram-negative marine bacterium Aliivibrio salmonicida, named ASCA that can promote CO₂ absorption in an alkaline solvent required for efficient carbon capture. We designed a mature form of ASCA (mASCA) using a codon optimization of ASCA gene and removal of ASCA signal peptide. mASCA was highly expressed (255 mg/L) with a molecular weight of approximately 26 kDa. The mASCA enzyme exhibited stable esterase activity within a temperature range of 10-60 °C and a pH range of 6-11. mASCA activity remained stable for 48 h at pH 10. We also investigated its inhibition profiles using inorganic anions, such as acetazolamide, sulfanilamide, iodide, nitrate, and azide. We also demonstrate that mASCA is capable of catalyzing the conversion of CO₂ to CaCO₃ (calcite form) in the presence of Ca²⁺. It should be noted that mASCA enzyme exhibits high production yield and sufficient stabilities against relatively high temperature and alkaline pH, which are required conditions for the development of more efficient enzymatic CCS systems.

Bioprecipitation of Calcium Carbonate Crystals by Bacteria Isolated from Saline Environments Grown in Culture Media Amended with Seawater and Real Brine

The precipitation of calcium carbonate and calcium sulphate by isolated bacteria from seawater and real brine obtained in a desalination plant growth in culture media containing seawater and brine as mineral sources has been studied. However, only bioprecipitation was detected when the bacteria were grown in media with added organic matter. Biomineralization process started rapidly, crystal formation taking place in the beginning a few days after inoculation of media; roughly 90% of total cultivated bacteria showed. Six major colonies with carbonate precipitation capacity dominated bacterial community structure cultivated in heterotrophic platable bacteria medium. Taxonomic identification of these six strains through partial 16S rRNA gene sequences showed their affiliation with Gram-positive Bacillus and Virgibacillus genera. These strains were able to form calcium carbonate minerals, which precipitated as calcite and aragonite crystals and showed bacterial fingerprints or bacteria calcification. Also, carbonic anhydrase activity was observed in three of these isolated bacteria. The results of this research suggest that microbiota isolated from sea water and brine is capable of precipitation of carbonate biominerals, which can occur in situ with mediation of organic matter concentrations. Moreover, calcium carbonate precipitation ability of this microbiota could be of importance in bioremediation of CO₂ and calcium in certain environments.

Review of the enzymatic machinery of Halothermothrix orenii with special reference to industrial applications

Over the past few decades the extremes at which life thrives has continued to challenge our understanding of physiology, biochemistry, microbial ecology and evolution. Innovative culturing approaches, environmental genome sequencing, and whole genome sequencing have provided new opportunities for the biotechnological exploration of extremophiles. The whole genome sequencing of H. orenii has provided valuable insights not only into the survival and adaptation strategies of thermohalophiles but has also led to the identification of genes encoding biotechnologically relevant enzymes. The present review focuses on the purified and characterized enzymes from H. orenii including amylases, β-glucosidase, fructokinase, and ribokinase--along with uncharacterized but industrially important enzymes encoded by the genes identified in the genome such as β-galactosidases, mannosidases, pullulanases, chitinases, α-L-arabinofuranosidases and other glycosyl hydrolases of commercial interest. This review highlights the importance of the enzymes and their applications in different sectors and why future research for exploring the enzymatic machinery of H. orenii should focus on the expression, purification, and characterization of the novel proteins in H. orenii and their feasible application to pertinent industrial sectors. H. orenii is an anaerobe; genome sequencing studies have also revealed the presence of enzymes for gluconeogenesis and fermentation to ethanol and acetate, making H. orenii an attractive strain for the conversion of starch into bioethanol.

The biological deep sea hydrothermal vent as a model to study carbon dioxide capturing enzymes

Deep sea hydrothermal vents are located along the mid-ocean ridge system, near volcanically active areas, where tectonic plates are moving away from each other. Sea water penetrates the fissures of the volcanic bed and is heated by magma. This heated sea water rises to the surface dissolving large amounts of minerals which provide a source of energy and nutrients to chemoautotrophic organisms. Although this environment is characterized by extreme conditions (high temperature, high pressure, chemical toxicity, acidic pH and absence of photosynthesis) a diversity of microorganisms and many animal species are specially adapted to this hostile environment. These organisms have developed a very efficient metabolism for the assimilation of inorganic CO₂ from the external environment. In order to develop technology for the capture of carbon dioxide to reduce greenhouse gases in the atmosphere, enzymes involved in CO₂ fixation and assimilation might be very useful. This review describes some current research concerning CO₂ fixation and assimilation in the deep sea environment and possible biotechnological application of enzymes for carbon dioxide capture.

Biomimetic CO₂ sequestration using purified carbonic anhydrase from indigenous bacterial strains immobilized on biopolymeric materials

The present study deals with immobilization of purified CA and whole cell of Pseudomonas fragi, Micrococcus lylae, and Micrococcus luteus 2 on different biopolymer matrices. Highest enzyme immobilization was achieved with P. fragi CA (89%) on chitosan-KOH beads, while maximum cell immobilization was achieved with M. lylae (75%) on chitosan-NH(4)OH beads. A maximum increase of 1.08-1.18 fold stability between 35 and 55°C was observed for M. lylae immobilized CA. The storage stability was improved by 2.02 folds after immobilization. FTIR spectra confirmed the adsorption of CA on chitosan-KOH beads following hydrophilic interactions. Calcium carbonate precipitation was achieved using chitosan-KOH immobilized P. fragi CA. More than 2 fold increase in sequestration potential was observed for immobilized system as compared to free enzyme. XRD spectra revealed calcite as the dominant phase in biomimetically produced calcium carbonate.