Concentration Of Carbonic Anhydrase Research Articles

The impact of various periods of mercury exposure on the osmoregulatory and blood gas parameters of tilapia (Oreochromis niloticus)

Mercury (Hg) poses a significant risk to aquatic ecosystems and living organisms as a result of human activities. Hg found in fish can be detrimental to human health when consumed, causing harmful effects. The potential impact of Hg on fish physiology is a significant concern, given its presence in fish. The rapid accumulation of Hg in fish tissues has the potential to impact their blood gas and electrolyte compositions. The objective of this investigation was to analyze the effects of sublethal concentrations of Hg on the blood gas and electrolyte levels of tilapia (Oreochromis niloticus) over different periods of exposure. This research was conducted through laboratory experiments. The study involved subjecting fish to sublethal concentrations of Hg at levels of 0.06 and 0.6 mg/L for a duration of 4 and 15 days. Upon completion of the toxicity test, fish specimens were taken from each testing group for the purpose of analyzing the Hg and carbonic anhydrase (CA) concentrations present in the gills, as well as osmoregulatory, acid-base, and hematological parameters. The results indicate that solely the fish that were subjected to a concentration of 0.6 mg/L Hg for a duration of 15 days exhibited a higher concentration of Hg in their gills compared to the control group. The inhibition of respiration by Hg was observed to be a result of the generation of metabolic acidosis, reduction in gill CA, decrease in pO2, as well as a decrease in plasma osmolality, Cl−, Na+, and K+. The levels of red blood cells, hemoglobin, and hematocrit exhibited a decrease solely at the concentration of 0.6 mg/L over a period of 15 days. The previously mentioned impairments have the potential to restrict the capacity of fish to adequately supply oxygen to their cells, thereby reducing overall performance.

Effect of Multi-Walled Carbon Nanotubes on lung tissue and concentration of enzyme Carbonic anhydrase in the New Zealand white rabbit

The aim of the present study was to investigate the effect of variable doses of Multi Carbon Nanotubes (MWCNTs) 1,3,5 mg/ml/kg body weight on lung weight and their effect on the concentration of Carbonic anhydrase(CA), morphological and histopathological changes of the males New Zealand white rabbits, In this study was used 40 New Zealand white rabbit of males, their ages range between (12-18 months) divided into four groups, ten for each group which intratracheal instillation with Nanoparticles, At days 7 and 90 post exposure, The blood , lung and trachea tissue samples were collected for each group.
 The exposure with Multi Walled Carbon Nanotubes led to significant increase in the lung weight of all groups by increasing the dose and the exposure period compared with control group, While the effect of carbon nanotubes in the lung function was represented by estimating the concentration of enzyme Carbonic anhydrase in blood serum that led to significant increase in the concentration of the enzyme for all groups compared with control group, And the effect of carbon nanotubes were studied on morphological and histological changes in each of the lung and trachea of exposure rabbit compared with control group, the morphological and histological changes in the lung and trachea of exposure rabbit with MWCNTs after 7 days of exposure, included whiting the upper surface of the lobes, sever infiltration of the mixed inflammatory cells (mono and polymorphonuclear), hyperatrophy of the tissue, muscular hyperatrophy of bronchi and fibrosis of the region, while after 90 days of exposure, the histological change were similar to that occurred after 7 days of exposure but more clear. Thus it shows that the lung was most affected organ by this tubes, which approved by histological examination of lung.

Life after death? Exploring biochemical and molecular changes following organismal death in green turtles, Chelonia mydas (Linnaeus, 1758)

Green turtles, Chelonia mydas, have been included in biomonitoring efforts given its status as an endangered species. Many studies, however, rely on samples from stranded animals, raising the question of how death affects important biochemical and molecular biomarkers. The goal of this study was to investigate post mortem fluctuations in the antioxidant response and metabolism of carbohydrates in the liver of C. mydas. Liver samples were obtained from six green turtles which were submitted to rehabilitation and euthanized due to the impossibility of recovery. Samples were collected immediately after death (t = 0) and at various time intervals (1, 2, 3, 4, 5, 6, 12, 18 and 24 h post mortem), frozen in liquid nitrogen and stored at −80 °C. The activities of catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR) and glucose-6-phosphate dehydrogenase (G6PDH) were analyzed, as were the levels of lipid peroxidation, glycogen concentration, RNA integrity (RNA IQ) and transcript levels of carbonic anhydrase and pyruvate carboxylase genes. Comparison between post mortem intervals showed a temporal stability for all the biomarkers evaluated, suggesting that changes in biochemical and molecular parameters following green turtle death are not immediate, and metabolism may remain somewhat unaltered up to 24 h after death. Such stability may be associated with the overall lower metabolism of turtles, especially under an oxygen deprivation scenario such as organismal death. Overall, this study supports the use of biomarkers in sea turtles sampled within a period of 24 h post mortem for biomonitoring purposes, though it is recommended that post mortem fluctuations of particular biomarkers be evaluated prior to their application, given that proteins may show varying degrees of susceptibility to proteolysis.

Factors, associated with elevated concentration of soluble carbonic anhydrase IX in plasma of women with cervical dysplasia

Precancerous lesions of human cervix uteri have a tendency for regression or progression. In cervical intraepithelial neoplasia grade 2 (CINII) case there is an uncertainty if a lesion will progress or regress. The carbonic anhydrase IX (CAIX) enzyme is overexpressed in cervical cancer which is more sensitive to radiotherapy. CAIX is associated with poor prognosis in solid hypoxic tumors. The aim of this study was to determine factors related to elevated soluble CAIX (s-CAIX) in high-grade intraepithelial lesion (HSIL) cases. Methods. Patients diagnosed with HSIL (N = 77) were included into the research group whereas without HSIL (N = 72)—the control group. Concentration of the soluble CAIX (s-CAIX) in plasma was determined by the DIANA ligand-antibody-based method. C. trachomatis was detected from cervical samples by PCR. Primary outcomes were risk factors elevating s-CAIX level in HSIL group. Non-parametric statistical analysis methods were used to calculate correlations. Results. The s-CAIX level in patients with HSIL was elevated among older participants (rs = 0.27, p = 0.04) and with C. trachomatis infection (p = 0.028). Among heavy smokers with HSIL, the concentration of s-CAIX was higher in older women (rs = 0.52, p = 0.005), but was not related to the age of heavy smokers’ controls (τ = 0.18 p = 0.40). Conclusion. The concentration of s-CAIX was higher among older, heavy smoking and diagnosed with C. trachomatis patients. All these factors increased the risk for HSIL progression.

Correlation of Carbonic Anhydrase VI Enzyme, Total Proteins, Antioxidant Levels of Saliva and Dental Caries in Caries-Free and Caries-Active Children - A Case-Control Study.

Factors in the biofilm influence the induction and advancement of the carious process. This study was done to relate and assess the levels of enzyme carbonic anhydrase VI, total protein, and antioxidants (superoxide dismutase [SOD], catalase, lipid peroxidase, and uric acid) in caries-free and caries-active children. This case-control study comprised 60 children of age group 6-12 years who were evaluated for decayed missing filled teeth (dmft)/DMFT criteria and distributed into two groups: Group 1 - caries active (case) and Group 2 - caries free (control) for saliva collection with 30 participants in each of the above groups. Stimulated saliva was obtained, and the samples were then evaluated using biochemical lab tests. The data were then statistically evaluated using independent t-test. Catalase in the caries-free group was significantly higher, but the concentration of carbonic anhydrase (CAVI) enzyme, total protein, and other antioxidant enzyme activity was enhanced in caries-active children in which uric acid demonstrated a statistically significant difference with higher levels in caries-active group. There is an increased concentration of CAVI enzyme in caries-active group and total protein showed a linear relation with caries activity. Antioxidant parameters such as SOD and lipid peroxidase were increased with caries activity. Uric acid was significantly higher in the caries-active group, whereas catalase showed an indirect relation with dental caries. Significant variations in the levels of these parameters imply that the levels of these components of saliva can act as strong markers of caries status in children.

A hybrid chemo-biocatalytic system of carbonic anhydrase submerged in CO2-phillic sterically hindered amines for enhanced CO2 capture and conversion into carbonates

The present study highlights a hybrid approach to capture and convert carbon dioxide (CO2) from exhaust gases using bovine carbonic anhydrase (CA) submerged into aqueous amine solvents. Particularly, the sterically hindered amines have unique properties to absorb CO2 and also play a key role in wide range of industrial applications. In this work, the reaction kinetics of CO2 were studied in the aqueous phase of sterically hindered amines (SHAs), 2-amino-2-hyroxymethyl-1,3-propanediol (AHPD) and 2-amino-2-methyl-1-propanol (AMP), mixed with bovine CA as test and without CA as control using the stopped flow technique. The results showed a significant improvement in the rate of reaction between SHAs (either aqueous AHPD or aqueous AMP) and CO2 in the presence of CA. Moreover, the absorption capacity of SHA for CO2 and its initial absorption rate in presence of CA was significantly enhanced. The rate constants of pseudo first-order reaction of CO2 reacting with AHPD and AMP (each 0.5 kmol/m3) with varied concentration of CA were determined at temperature range of 298- 353 K. The aqueous AHPD and AMP systems in the presence of CA and control retained 65% of absorption capacity after 5 repetitive cycles. Also, the amine solvent captured CO2 was converted into calcium carbonate (CaCO3) which is white powder materials. The synthesized CaCO3 was characterized for its morphological and physicochemical properties using scanning electron microscopy (SEM) and Fourier transformer infrared spectroscopy (FTIR) etc. Overall, as the CA present is the amine solvent can efficiently convert the CO2 and that can be removed easily in the form of CaCO3 precipitates.

Trajectory and timescale of oxygen and clumped isotope equilibration in the dissolved carbonate system under normal and enzymatically-catalyzed conditions at 25 °C

The abundance of 18O isotopes and 13C-18O isotopic “clumps” (measured as δ18O and Δ47, respectively) in carbonate minerals have been used to infer mineral formation temperatures. An inherent requirement or assumption for these paleothermometers is mineral formation in isotopic equilibrium. Yet, apparent disequilibrium is not uncommon in biogenic and abiogenic carbonates formed in nature and in synthetic carbonates prepared under laboratory settings, as the dissolved carbonate pool (DCP) from which minerals precipitate is often out of δ18O and Δ47 equilibrium. For this, a complete understanding of both equilibrium and kinetics of isotopic partitioning and 13C-18O clumping in DCP is crucial. To this end, we analyzed Δ47 of inorganic BaCO3 samples from Uchikawa and Zeebe (2012) (denoted as UZ12), which were quantitatively precipitated from NaHCO3 solutions at various times over the course of isotopic equilibration at 25 °C and pHNBS of 8.9. Our data show that, although the timescales for δ18O and Δ47 equilibrium in DCP are relatively similar, their equilibration trajectories are markedly different. As opposed to a simple unidirectional and asymptotic approach toward δ18O equilibrium (first-order kinetics), Δ47 equilibration initially moves away from equilibrium and then changes its course towards equilibrium. This excess Δ47 disequilibrium is manifested as a characteristic “dip” in the Δ47 equilibration trajectory, a feature consistent with an earlier study by Staudigel and Swart (2018) (denoted as SS18). From the numerical model of SS18, the non-first-order kinetics for Δ47 equilibration can be understood as a result of the difference in the exchange rate for oxygen isotopes bound to 12C versus 13C, or an isotope effect of ~25‰. We also developed an independent model for the Exchange and Clumping of 13C and 18O in DCP (ExClump38 model) to trace the evolution of singly- and doubly-substituted isotopic species (i.e., δ13C, δ18O and Δ47). The model suggests that the dip in the Δ47 equilibration trajectory is due largely to kinetic carbon isotope fractionation for hydration and hydroxylation of CO2. We additionally examined the BaCO3 samples prepared from NaHCO3 solutions supplemented with carbonic anhydrase (CA), an enzyme known to facilitate δ18O equilibration in DCP by catalyzing CO2 hydration (UZ12). These samples revealed that, while CA effectively shortens the time required for Δ47 equilibrium in DCP, the overall pattern and magnitude of the dip in the Δ47 equilibration trajectory remain unchanged. This suggests no additional isotope effects due to the CA enzyme within the tested CA concentrations. With the ExClump38 model, we test various physicochemical scenarios for the timescales and trajectories of isotopic equilibration in DCP and discuss their implications for the Δ47 paleothermometry.

Carbonic Anhydrase IX and Hypoxia Promote Rat Pulmonary Endothelial Cell Survival during Infection.

Low tidal volume ventilation protects the lung in mechanically ventilated patients. The impact of the accompanying permissive hypoxemia and hypercapnia on endothelial cell recovery from injury is poorly understood. CA (carbonic anhydrase) IX is expressed in pulmonary microvascular endothelial cells (PMVECs), where it contributes to CO2 and pH homeostasis, bioenergetics, and angiogenesis. We hypothesized that CA IX is important for PMVEC survival and that CA IX expression and release from PMVECs are increased during infection. Although the plasma concentration of CA IX was unchanged in human and rat pneumonia, there was a trend toward increasing CA IX in the bronchoalveolar fluid of mechanically ventilated critically ill patients with pneumonia and a significant increase in CA IX in the lung tissue lysates of pneumonia rats. To investigate the functional implications of the lung CA IX increase, we generated PMVEC cell lines harboring domain-specific CA IX mutations. By using these cells, we found that infection promotes intracellular (IC) expression, release, and MMP (metalloproteinase)-mediated extracellular cleavage of CA IX in PMVECs. IC domain deletion uniquely impaired CA IX membrane localization. Loss of the CA IX IC domain promoted cell death after infection, suggesting that the IC domain has an important role in PMVEC survival. We also found that hypoxia improves survival, whereas hypercapnia reverses the protective effect of hypoxia, during infection. Thus, we report 1) that CA IX increases in the lungs of pneumonia rats and 2) that the CA IX IC domain and hypoxia promote PMVEC survival during infection.

Quick Refolding of High-Concentration Proteins via Microchannel Dialysis

The industrial production of active proteins from E. coli necessitates the refolding of high concentrations of protein over a short period of time. However, it is difficult to simultaneously achieve high concentration and short residence time. The dialysis method can refold high concentrations of proteins, but this process takes a long time. The dilution method can quickly refold proteins, but the resultant proteins are inevitably diluted. In the present study, by designing microchannels in dialysis membranes, which can enlarge the surface area for quickly removing protein denaturant, high concentrations of active carbonic anhydrase---eight times more concentrated than achieved using dilution method---were refolded in 20 minutes, which is orders of magnitude faster than the conventional dialysis method.

The enhanced enzymatic performance of carbonic anhydrase on the reaction rate between CO2 and aqueous solutions of sterically hindered amines

AbstractThe kinetics of the reactions of carbon dioxide (CO2) with aqueous solutions of two different sterically hindered amines (SHAs), 2‐amino‐2‐ethyl‐1,3‐propanediol (AEPD) and 2‐amino‐2‐methyl‐1,3‐propanediol (AMPD), in the presence and absence of carbonic anhydrase (CA) was investigated experimentally using stopped‐flow conductimetry. The amine concentration, CA concentration, and temperature were varied within the ranges of 0.1–0.5 kmol·m–3, 0–125 g·m–3, and 298–353 K, respectively. Based on pseudo first‐order reaction conditions, the intrinsic reaction rate (ko) was obtained according to a modified termolecular reaction mechanism. The obtained results showed that the reaction rate between the SHA solutions (either aqueous AEPD or aqueous AMPD) and CO2 was enhanced significantly upon adding small amounts of CA as a promoter. Such a result supports the use of the aforementioned solvent system as a candidate for CO2 capture. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Foliar application of nano-Zn and mycorrhizal inoculation enhanced Zn in grain and yield of two barley (Hordeum vulgare) cultivars under field conditions

Zinc (Zn) deficiency is a global micronutrient problem in agricultural systems. The main target of this experiment was to investigate the effectiveness of foliar application of Zn under field conditions. Grain yield and Zn concentration in seed were assessed with three replicate plots per treatment in a factorial (2 x 3 x 2) experiment for two barley cultivars (Yusuf and Julgeh), three foliar ZnO applications (nano, ordinary and nano+ordinary ZnO) and two commercial inocula of arbuscular mycorrhizal (AM) fungi (F. mosseae and R. irregularis). Among all Zn foliar applications, Zn applied in both nano and nano+ordinary forms were labile and resulted in the highest Zn concentration in grain of both barley cultivars. Cultivar Julgeh had higher grain Zn concentrations than did cultivar Yusuf in the same treatments. Nano ZnO was more effective than the ordinary form of ZnO and had the highest potential to improve physiological traits, plant growth and yield parameters in both cultivars. There was also a positive impact of the nano form of ZnO on phytase activity and carbonic anhydrase concentration in both barley cultivars. Inoculation with commercial inocula of AM fungi also enhanced grain Zn concentration, with Julgeh more responsive to inoculation with F. mosseae, and Yusuf more responsive to inoculation with R. irregularis. Generally, the combined application of Zn and inoculation with AM fungi improved physiological traits, grain yield and Zn availability to these two barley cultivars grown under field conditions. Accordingly, the nano form of Zn positively enhanced shoot morphological parameters, physiological parameters and grain Zn concentration. Application of the nano form ZnO in combination with inoculation with AM fungi had the most beneficial effects on grain Zn concentration, so this combined practice may have potential to reduce the requirement for application of synthetic Zn chemical fertilizers.

Dietary addition of zinc-methionine influenced eggshell quality by affecting calcium deposition in eggshell formation of laying hens.

The present study explored the mechanism of Zn-methionine (Zn-Met) influencing eggshell quality of laying hens and investigated whether the mechanism was related to Ca deposition. Hyline grey layers (n 384, 38 weeks old) were divided into four groups: 0 mg Zn/kg, 40, 80 mg Zn/kg as Zn-Met, and 80 mg Zn/kg as zinc sulphate (ZnSO4). Eggshell quality, Zn contents, Zn-containing enzyme activities and expressions of shell matrix proteins in eggshell gland (ESG) were analysed. Zn-Met treatment at 80 mg/kg increased (P < 0·05) egg weight and eggshell strength throughout the experiments. The 80 mg/kg Zn-Met group (P < 0·05) had decreased mammillary knob width and larger relative atomic weight percentage of Ca, stronger signal intensity of Ca in linear distribution and the Ca was more evenly distributed in the transversal surface of eggshell. Zn contents (P < 0·001) in yolk and serum, Ca, albumin (Alb) levels in ESG as well as carbonic anhydrase (CA) activity in serum (P < 0·05) and mRNA levels of CA and Ca-binding protein-d28k (CaBP-D28k) (P < 0·001) in the 80 mg/kg Zn-Met group were the highest among all treatments. In conclusion, shell strength as one of eggshell qualities was mostly related to mammillary cone width in ultrastructure caused by the pattern of Ca deposition in eggshell formation. Also, the increase in Zn-Met-induced Ca deposition may be due to the increased Zn contents in serum and tissues, which were attributable to the increased CA concentrations in serum, Ca, Alb levels and up-regulated CA and CaBP-D28k mRNA levels in ESG.

Enzymatically catalyzed CO2 -H2 O equilibration for oxygen isotope analyses of aqueous samples.

The classic CO2 -H2 O equilibration method is a very popular technique for the measurement of the oxygen isotope composition of aqueous samples in stable isotope geochemistry. This study examined whether enzymatically controlled CO2 -H2 O equilibration by carbonic anhydrase (CA) could reduce the time for oxygen isotope equilibrium between CO2 and H2 O at 25°C. Four types of aqueous samples containing CA were equilibrated with CO2 gases using a continuous flow isotope ratio mass spectrometer equipped with an automated gas sample collection device. We examined the effect of CA concentration in an aqueous sample, the influence of drying technique for the preparation of sample vials containing dried CA, the age of CA stock solution, and the ionic strength and the oxygen isotope composition of aqueous samples. CA rapidly catalyzed the oxygen isotope exchange between CO2 and H2 O and was unaffected by drying technique or stock solution age. Compared with aqueous samples with no CA or 0.2 μmolal CA, samples containing 4μmolal CA significantly reduced the CO2 -H2 O equilibration time for deionized water and artificial seawater (ionic strength = ~0.6) from ~19 h and ~23 h to ~0.30 h and ~0.77 h, respectively at 25°C. This enzymatically catalyzed CO2 -H2 O equilibration method is time-efficient, cost-effective, requires no additional data correction procedure, and can be used for most commercially available CO2 -H2 O equilibration devices without any modification.

Effects of methionine hydroxyl analog chelated zinc on laying performance, eggshell quality, eggshell mineral deposition, and activities of Zn-containing enzymes in aged laying hens.

The study aimed to determine the effects of methionine hydroxyl analog chelated zinc (MHA-Zn) on laying performance, eggshell quality and mineral deposits, and the activities of Zn-containing enzymes on aged laying hens. A total of 960 layers (Hy-Line Grey, 57 wk old) were fed a basal diet (Zn: 35.08mg/kg) without extra zinc for 2 wk. During the ensuing 14 wk, birds were randomly divided into 4 groups according to body weight and laying rate, with 8 replicates per treatment, and each group had 8 replicates of 30 hens. Four levels of Zn (ZnSO4: 80mg/kg; MHA-Zn: 20, 40, 80mg/kg) were added to the diet, respectively. The results shown that dietary Zn did not affect laying rate, average egg weight, average daily feed intake, or feed conversion ratio (P>0.05); however, compared to the inorganic group, dietary supplementation with 40 or 80mg/kg MHA-Zn decreased broken egg rate significantly in the whole period (P<0.05), while significantly increased eggshell weight in week 62 to 72, eggshell thickness and eggshell strength in wk 66 to 72, eggshell weight percent and eggshell density in week 62 to 72 (P<0.05). Besides, dietary supplementation with different sources and levels of Zn did not affect ash concentration of eggshell (P>0.05), whereas dietary supplementation with 80mg/kg MHA-Zn improved the Zn and Ca concentrations of eggshells and carbonic anhydrase (CA) activity of liver, and 40mg/kg MHA-Zn increased Zn concentration of liver (P<0.05). Moreover, no significant differences in alkaline phosphatase activity were observed among the treatment groups (P>0.05). Therefore, dietary supplementation with 40mg/kg MHA-Zn can improve eggshell quality by promoting Ca deposition and CA activity.

Enrichment of Extracellular Carbonic Anhydrase in the Sea Surface Microlayer and Its Effect on Air‐Sea CO2 Exchange

AbstractThis paper describes the quantification of extracellular carbonic anhydrase (eCA) concentrations in the sea surface microlayer (SML), the boundary layer between the ocean and the atmosphere of the Indo‐West Pacific. We demonstrated that the SML is enriched with eCA by 1.5 ± 0.7 compared to the mixed underlying water. Enrichment remains up to a wind speed of 7 m s−1 (i.e., under typical oceanic conditions). As eCA catalyzes the interconversion of HCO3− and CO2, it has been hypothesized that its enrichment in the SML enhances the air‐sea CO2 exchange. We detected concentrations in the range of 0.12 to 0.76 nM, which can enhance the exchange by up to 15% based on the model approach described in the literature.

Laboratory to bench-scale evaluation of an integrated CO2 capture system using a thermostable carbonic anhydrase promoted K2CO3 solvent with low temperature vacuum stripping

An advanced post-combustion CO2 capture process with combined attributes of a thermostable carbonic anhydrase (CA) enzyme catalyst, low-enthalpy K2CO3 solvent, and vacuum stripping utilizing low exergy steam was evaluated from laboratory concept to application performance testing in an integrated 30 standard liters per minute gas flow bench-scale system operated for 500 h. Laboratory concept studies were performed using a wetted wall column to characterize solvent CO2 absorption kinetics and using a recirculating temperature loop to evaluate CA thermo-stability. Wetted wall column tests showed a dramatic 5-fold increase in CO2 mass transfer coefficient when combining 2 g/L CA with aqueous 23.5 wt% K2CO3 solvent. Further increasing the CA concentration resulted in a gradual increase in mass transfer coefficient until a performance plateau was observed beyond a 4 g/L CA dose. Operating temperature had limited impact on CO2 capture over the range 30–50 °C. Surface tension measurements of 23.5 wt% K2CO3 solvent exhibited a gradual decrease with increasing CA concentration. Thermo-stability tests in a temperature cycling loop designed to mimic the temperature swings between absorption and desorption showed that CA longevity could be extended by decreasing the total cycle time spent at high temperature. Parametric tests in the bench-scale unit resulted in a CO2 capture efficiency increase of 4.6-fold when increasing the CA concentration from zero to 2.5 g/L. Capture efficiency increased with higher reboiler duty (i.e. reboiler temperature) and lower absorber temperature. Tests with a 30 °C absorber temperature delivered >90% capture. Variation in solvent flow rate had little impact on capture efficiency because the reaction closely reached equilibrium at the top of the absorber. The integrated bench-scale system operated successfully for an accumulated 500 h under conditions of 40 °C absorber temperature and stripper at 35 kPa pressure with an approximate 77 °C stripper bottom temperature, delivering an average 84% CO2 capture with 23.5 wt% K2CO3-based solvent containing 2.5 g/L CA. Dissolved CA replenishment and conventional process controls were demonstrated as straightforward approaches to maintain system performance of this benign, low-temperature, CA-promoted process for CO2 capture.

The development of kinetics model for CO2 absorption into tertiary amines containing carbonic anhydrase

CO2 absorption into aqueous solutions of two tertiary alkanolamines, namely, MDEA and DMEA with and without carbonic anhydrase (CA) was investigated with the use of the stopped‐flow technique at temperatures in the range of 293–313 K, CA concentration varying from 0 to 100 g/m3 in aqueous MDEA solution with the amine concentration ranging from 0.1 to 0.5 kmol/m3, and CA concentration varying from 0 to 40 g/m3 in aqueous DMEA solution with the amine concentration ranging from 0.05 to 0.25 kmol/m3. The results show that the pseudofirst‐order reaction rate (k0, amine; s−1) is significantly enhanced in the presence of CA as compared with that without CA. The enhanced values of the kinetic constant in the presence of CA has been calculated and a new kinetics model for reaction of CO2 absorption into aqueous tertiary alkanolamine solutions catalyzed by CA has been established and used to make comparisons of experimental and calculated pseudo first‐order reaction rate constant (k0, with CA) in CO2‐MDEA‐H2O and CO2‐DMEA‐H2O solutions. The AADs were 15.21 and 15.17%, respectively. The effect of pKa on the CA activities has also been studied by comparison of CA activities in different tertiary amine solutions, namely, TEA, MDEA, DMEA, and DEEA. The pKa trend for amines were: DEEA &gt; DMEA &gt; MDEA &gt; TEA. In contrast, the catalyst enhancement in amines was in the order: TEA&gt; MDEA&gt; DMEA&gt; DEEA. Therefore, it can be seen that the catalyst enhancement in the amines decreased with their increasing pKa values. © 2017 American Institute of Chemical Engineers AIChE J, 2017

Children with a Higher Activity of Carbonic Anhydrase VI in Saliva Are More Likely to Develop Dental Caries

Objective: This study aimed to analyze the concentration and activity of carbonic anhydrase (CA) VI in the saliva of school children. We investigated the relationship among caries, CA VI concentration/activity, flow rate, pH, and buffering capacity. Materials and Methods: Seventy-four school children were divided into a caries-free group and a caries group. Clinical examinations were conducted by one examiner according to World Health Organization criteria + early caries lesions. Salivary flow rate, pH, and buffering capacity were analyzed. Salivary CA VI concentration and activity were evaluated by ELISA and zymography, respectively. The data were analyzed using Student's t test and the Mann-Whitney test, and Pearson and Spearman correlation analyses were also done. In multivariate modeling, associations between variables were expressed as odds ratios. Results: The results showed that salivary flow rate, salivary pH, and BC were significantly higher in the saliva of caries-free children. Also, the salivary CA VI concentration was significantly higher in the saliva of caries-free children. The salivary CA VI activity was higher in children with caries. We found a negative correlation between BC and dental caries. Also, in the caries group we found a positive correlation between the concentration and the activity of CA VI and a negative correlation between BC and CA VI activity. A negative correlation between salivary pH and CA VI concentration was observed in the caries-free group. A high activity of CA and a low salivary flow rate were associated with dental caries. Conclusion: These results support the conclusion that dental caries is highly affected by the activity of CA VI in saliva as well as by the salivary flow rate.

Enzymatic Activity of Immobilized Carbonic Anhydrase onto Amberlite XAD7

Carbon capture by using carbonic anhydrase (CA) enzyme has become an alternative and environmental friendly approach in carbon sequestration technology. Among various form of CA, immobilized CA onto the support materials offer better behaviour of enzyme including enhance enzyme stability, increase biocatalytic activity and improved enzyme reusability. These factors are important in carbon sequestration in order to reduce the operation cost and achieve optimum CO2 utilization. Thus, behaviour of the CA immobilized onto the solid support is important in order to determine its activity towards CO2 capture. In this study, different initial concentration of CA immobilized onto amberlite XAD7 was investigated for the optimum CO2 sequestration through protein analysis and enzyme activity towards p-NPA substrate. The CA initial concentration was varied from 0.32 to 1.87 mg/ml while other parameters were kept constant where temperature at 25°C, speed shaking at 100 rpm, pH at 8.0 and support dosage at 0.5g. The CA initial concentration at 0.32 mg/ml gave the highest percentage of immobilized enzyme (99%). While, the highest enzyme activity towards its substrate obtained was 1.58mmol/min using 99% CA attached to amberlite XAD7.

Integrated Bench-Scale Parametric Study on CO2 Capture Using a Carbonic Anhydrase Promoted K2CO3 Solvent with Low Temperature Vacuum Stripping

A bench-scale unit was fabricated and used to investigate use of carbonic anhydrase (CA) promoted K2CO3 solvent as an option for CO2 capture from coal-fired power plants. Bench-scale parametric tests were performed at various CA concentrations, solvent flow rates, and reboiler duties. The CO2 capture efficiency significantly increases, and regeneration energy requirement decreases, with increasing CA concentrations up to 2.5 g/L, with capture performance leveling off at higher enzyme doses (up to 4 g/L). Thus, at higher enzyme doses, the capture efficiency is equilibrium rather than kinetically controlled at the top of absorber, when using solvent regenerated via vacuum stripping at high (>35%) lean carbonate to bicarbonate (CTB) conversion levels, which limits the driving force for CO2 absorption. The CO2 capture efficiency also increases when reboiler duty was increased from 0.85 to 1.1 kW, although this also increases the regeneration energy penalty. In contrast, the effect of solvent flow rate on CO2 capture efficiency is less pronounced. Further improvements to the CO2 capture process using CA promoted K2CO3 solvent with low temperature vacuum stripping could be potentially advanced by lowering vacuum pressure, improving strategies for increasing rich CTB conversion (e.g., advanced packing column and optimized L/G ratio), and decreasing absorption temperature.