Chemical treatment of Escherichia coli: 3. Selective extraction of a recombinant protein from cytoplasmic inclusion bodies in intact cells

In previous parts of this study we developed procedures for the high‐efficiency chemical extraction of soluble and insoluble protein from intact Escherichia coli cells. Although high yields were obtained, extraction of recombinant protein directly from cytoplasmic inclusion bodies led to low product purity due to coextraction of soluble contaminants. In this work, a two‐stage procedure for the selective extraction of recombinant protein at high efficiency and high purity is reported. In the first stage, inclusion‐body stability is promoted by the addition of 15 mM 2‐hydroxyethyldisulfide (2‐HEDS), also known as oxidized β‐mercaptoethanol, to the permeabilization buffer (6 M urea + 3 mM ethylenediaminetetraacetate [EDTA]). 2‐HEDS is an oxidizing agent believed to promote disulfide bond formation, rendering the inclusion body resistant to solubilization in 6 M urea. Contaminating proteins are separated from the inclusion‐body fraction by centrifugation. In the second stage, disulfide bonds are readily eliminated by including reducing agent (20 mM dithiothreitol [DTT]) into the permeabilization buffer. Extraction using this selective two‐stage process yielded an 81% (w/w) recovery of the recombinant protein Long‐R³‐IGF‐I from inclusion bodies located in the cytoplasm of intact E. coli, at a purity of 46% (w/w). This was comparable to that achieved by conventional extraction (mechanical disruption followed by centrifugation and solubilization). A pilot‐scale procedure was also demonstrated using a stirred reactor and diafiltration. This is the first reported study that achieves both high extraction efficiency and selectivity by the chemical treatment of cytoplasmic inclusion bodies in intact bacterial cells. © 1999 John Wiley & Sons, Inc. Biotechnol Bioeng 62: 455–460, 1999.     

KINETICS OF SILICIC ACID UPTAKE AND RATES OF SILICA DISSOLUTION IN THE MARINE DIATOM THALASSIOSIRA PSEUDONANA1,2

Tracer techniques using the stable isotope ³⁰Si were used to measure rates of silicic acid uptake and silica dissolution in silicon replete and silicon depleted populations of 2 clones of the marine diatom Thalassiosira pseudonana Hasle & Heimdal. Uptake kinetics were describable using the Michaelis-Menten equation for enzyme kinetics, and no threshold concentration for uptake was evident. The maximum specific uptake rate of the estuarine clone 3H (0.062–0.092 · h^?1) was higher than that of the Sargasso Sea clone 13-1 (0.028–0.031 · h^?1), but half-saturation constants for uptake by the 2 clones were not measurably different (0.8–2.3 μM for 3H; 1.4–1.5 μM for 13-1). There was little or no light dependence of uptake in populations grown under optimal light conditions prior to the experiment. Exponentially growing populations released silicic acid to the medium by dissolution of cellular silica at rates ranging from 6.5 to 15% of the maximum uptake rate.     

Recovery of active N-acetyl-D-glucosamine 2-epimerase from inclusion bodies by solubilization with non-denaturing buffers

Overexpression of recombinant N-acetyl-d-glucosamine 2-epimerase, one of the key enzymes for the synthesis of N-acetylneuraminic acid, in E. coli led to the formation of protein inclusion bodies. In this study we report the recovery of active epimerase from inclusion bodies by direct solubilization with Tris buffer. At pH 7.0, 25% of the inclusion bodies were solubilized with Tris buffer. The specific activity of the solubilized proteins, 2.08 ± 0.02 U/mg, was similar to that of the native protein, 2.13 ± 0.01 U/mg. The result of circular dichroism spectroscopy analysis indicated that the structure of the solubilized epimerase obtained with pH 7.0 Tris buffer was similar to that of the native epimerase purified from the clarified cell lysate. As expected, the extent of deviation in CD spectra increased with buffer pH. The total enzyme activity recovered by solubilization from inclusion bodies, 170.41 ± 10.06 U/l, was more than 2.5 times higher than that from the clarified cell lysate, 67.32 ± 5.53 U/l. The results reported in this study confirm the hypothesis that the aggregation of proteins into inclusion bodies is reversible and suggest that direct solubilization with non-denaturing buffers is a promising approach for the recovery of active proteins from inclusion bodies, especially for aggregation-prone multisubunit proteins.     

Physico-Chemical Characterization and In Vitro Dissolution Assessment of Clonazepam—Cyclodextrins Inclusion Compounds

The objectives of this research were to prepare and characterize inclusion complexes of clonazepam with β-cyclodextrin and hydroxypropyl-β-cyclodextrin and to study the effect of complexation on the dissolution rate of clonazepam, a water-insoluble lipid-lowering drug. The phase-solubility profiles with both cyclodextrins were classified as A_P-type, indicating the formation of 2:1 stoichiometric inclusion complexes. Gibbs free energy ( DG_tr^o ) \left( {\Delta {G_{tr}}^o} \right) values were all negative, indicating the spontaneous nature of clonazepam solubilization, and they decreased with increase in the cyclodextrins concentration, demonstrating that the reaction conditions became more favorable as the concentration of cyclodextrins increased. Complexes of clonazepam were prepared with cyclodextrins by various methods such as kneading, coevaporation, and physical mixing. The complexes were characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry studies. These studies indicated that complex prepared kneading and coevaporation methods showed successful inclusion of the clonazepam molecule into the cyclodextrins cavity. The complexation resulted in a marked improvement in the solubility and wettability of clonazepam. Among all the samples, complex prepared with hydroxypropyl-β-cyclodextrin by kneading method showed highest improvement in in vitro dissolution rate of clonazepam. Mean dissolution time of clonazepam decreased significantly after preparation of complexes and physical mixture of clonazepam with cyclodextrins. Similarity factor indicated significant difference between the release profiles of clonazepam from complexes and physical mixture and from plain clonazepam. Tablets containing complexes prepared with cyclodextrins showed significant improvement in the release profile of clonazepam as compared to tablet containing clonazepam without cyclodextrins.     

A novel method to recover inclusion body protein from recombinant <Emphasis Type="Italic">E. coli</Emphasis> fed-batch processes based on phage <Emphasis Type="Italic">Φ</Emphasis>X174-derived lysis protein E

Production of recombinant proteins as inclusion bodies is an important strategy in the production of technical enzymes and biopharmaceutical products. So far, protein from inclusion bodies has been recovered from the cell factory through mechanical or chemical disruption methods, requiring additional cost-intensive unit operations. We describe a novel method that is using a bacteriophage-derived lysis protein to directly recover inclusion body protein from Escherichia coli from high cell density fermentation process: The recombinant inclusion body product is expressed by using a mixed feed fed-batch process which allows expression tuning via adjusting the specific uptake rate of the inducing substrate. Then, bacteriophage ΦX174-derived lysis protein E is expressed to induce cell lysis. Inclusion bodies in empty cell envelopes are harvested via centrifugation of the fermentation broth. A subsequent solubilization step reveals the recombinant protein. The process was investigated by analyzing the impact of fermentation conditions on protein E-mediated cell lysis as well as cell lysis kinetics. Optimal cell lysis efficiencies of 99% were obtained with inclusion body titers of >2.0 g/l at specific growth rates higher 0.12 h^?1 and inducer uptake rates below 0.125 g/(g × h). Protein E-mediated cell disruption showed a first-order kinetics with a kinetic constant of ?0.8 ± 0.3 h^?1. This alternative inclusion body protein isolation technique was compared to the one via high-pressure homogenization. SDS gel analysis showed 10% less protein impurities when cells had been disrupted via high-pressure homogenization, than when empty cell envelopes including inclusion bodies were investigated. Within this contribution, an innovative technology, tuning recombinant protein production and substituting cost-intensive mechanical cell disruption, is presented. We anticipate that the presented method will simplify and reduce the production costs of inclusion body processes to produce technical enzymes and biopharmaceutical products.     

Gelucire44/14 improves fat absorption in rats with impaired lipolysis

Clinically relevant fat malabsorption is usually due to impaired intestinal fat digestion (lipolysis) and/or to impaired solubilization of the lipolytic metabolites. We hypothesized that Gelucire^®44/14 – a semi-solid self-micro-emulsifying excipient – could increase fat absorption. In relevant rat models for impaired lipolysis or for impaired solubilization we tested whether administration of Gelucire^®44/14 enhanced fat absorption. Rats with impaired lipolysis (lipase inhibitor Orlistat diet) and rats with reduced solubilization (permanent bile diversion) underwent a 72 h fat balance test to assess fat absorption. The absorption kinetics of a stable isotope-labeled fatty acid was assessed in rats with reduced solubilization, in the presence or absence of Gelucire^®44/14. Gelucire^®44/14 improved fat absorption in rats with impaired lipolysis (from 70% to 82%, p < 0.001). In rats with reduced solubilization, Gelucire^®44/14 did not increase fat absorption nor did it reconstitute the absorption kinetics of ¹³C-labeled palmitate, compared with control rats administered buffer without Gelucire^®44/14. The present data show that Gelucire^®44/14 might enhance fat absorption under conditions of impaired lipolysis, but not during impaired solubilization. We speculate that, due to its self-micro-emulsification properties, Gelucire^®44/14 stabilizes and improves residual lipolytic enzyme activity in vivo, which could be of therapeutic value in clinical conditions of fat malabsorption due to impaired lipolysis.     

Refolding and Purification of Zymomonas mobilis Levansucrase Produced as Inclusion Bodies in Fed-Batch Culture of Recombinant Escherichia coli

Zymomonas mobilis levansucrase was overproduced by the fed-batch culture of recombinant Escherichia coli harboring a novel expression system that is constitutively expressed by the promoter from the Rahnella aquatilis levansucrase gene. Most of the levansucrase was produced as inclusion bodies in the bacterial cytoplasm, accounting for approximately 20% of the total cellular protein. Refolding after complete denaturation by high concentrations of urea or guanidine hydrochloride was not successful, resulting in large amounts of insoluble aggregates. During the development of the refolding method, it was found that direct solubilization of the inclusion bodies with Triton X-100 reactivated the enzyme, with a considerable refolding efficiency. About 65% of inclusion body levansucrase was refolded into active levansucrase in the renaturation buffer containing 4% (v/v) Triton X-100. The in vitro refolded enzyme was purified to 95% purity by single-step DEAE–Sepharose ion exchange chromatography. Triton X-100 was removed by this ion exchange chromatography.     

Optimized procedures for purification and solubilization of basic fibroblast growth factor inclusion bodies

The efficiency of purification of basic fibroblast growth factor (bFGF) inclusion bodies using EDTA and nonionic detergents was improved from 25 to 40% by shifting the pH from 8.5 to strong alkaline conditions (pH 9.5 – 10.5). Complete dissolution of bFGF inclusion bodies by guanidinium hydrochloride (> 3 m) was independent of pH and the presence of reducing agents. In contrast, solubilization of bFGF inclusion bodies by urea was pH-dependent and increased in efficiency (e.g. from 0 to 100%) by increasing the pH (from pH 5.0 to 10.5 at 9 m urea). The purification and solubilization procedures are efficient for inclusion body concentrations corresponding to 10 and 100 g per l dry cell weight, respectively.     

Improved Recovery of a Fusion Protein Containing the Antigenic Domain 1 of the Human Cytomegalovirus Glycoprotein B

Heterologous expression in Escherichia coli often leads to production of the expressed proteins as insoluble and inactive inclusion bodies. The general strategy for protein recovery includes isolation and washing of inclusion bodies, solubilization of aggregated protein and refolding of solubilized protein. The process of refolding, as well as the other steps involved in inclusion body recovery, must be optimized according to the characteristics of each protein. For the development of reliable and inexpensive serodiagnostic tests, the antigenic domain 1 (AD-1) of human cytomegalovirus glycoprotein B was expressed in E. coli and a process was developed to increase recovery of the fusion protein containing AD-1. A comparison of disruption methods and different conditions involved in recovery of this fusion protein from inclusion bodies is presented. The developed method gives a high yield of the fusion protein with a purity sufficient for use in diagnostic tests.     

Preparative Enantioseparation of β‐Substituted‐2‐Phenylpropionic Acids by Countercurrent Chromatography With Substituted β‐Cyclodextrin as Chiral Selectors

Preparative enantioseparation of four β‐substituted‐2‐phenylpropionic acids was performed by countercurrent chromatography with substituted β‐cyclodextrin as chiral selectors. The two‐phase solvent system was composed of n‐hexane‐ethyl acetate‐0.10 mol L‐1 of phosphate buffer solution at pH 2.67 containing 0.10 mol L^‐1 of hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) or sulfobutylether‐β‐cyclodextrin (SBE‐β‐CD). The influence factors, including the type of substituted β‐cyclodextrin, composition of organic phase, concentration of chiral selector, pH value of the aqueous phase, and equilibrium temperature were optimized by enantioselective liquid–liquid extraction. Under the optimum separation conditions, 100 mg of 2‐phenylbutyric acid, 100 mg of tropic acid, and 50 mg of 2,3‐diphenylpropionic acid were successfully enantioseparated by high‐speed countercurrent chromatography, and the recovery of the (±)‐enantiomers was in the range of 90–91% for (±)‐2‐phenylbutyric acid, 91–92% for (±)‐tropic acid, 85–87% for (±)‐2,3‐diphenylpropionic acid with purity of over 97%, 96%, and 98%, respectively. The formation of 1:1 stoichiometric inclusion complex of β‐substituted‐2‐phenylpropionic acids with HP‐β‐CD was determined by UV spectrophotometry and the inclusion constants were calculated by a modified Benesi‐Hildebrand equation. The results showed that different enantioselectivities among different racemates were mainly caused by different enantiorecognition between each enantiomer and HP‐β‐CD, while it might be partially caused by different inclusion capacity between racemic solutes and HP‐β‐CD. Chirality 27:795–801, 2015. © 2015 Wiley Periodicals, Inc.     

Effect of growth temperature,induction, and molecular chaperones on the solubilization of over-expressed cellobiose phosphorylase from <Emphasis Type="Italic">Cellvibrio Gilvus</Emphasis> under <Emphasis Type="Italic">in vivo</Emphasis> conditions

In vivo folding of many proteins can be facilitated by growth temperature, extent of induction, and molecular chaperones, which prevent over-expressed protein from being trapped into insoluble inclusion bodies. In the present report, we describe the role of molecular chaperones and growth temperature on the solubilization of overexpressed Cellobiose Phosphorylase (CBP) in Escherichia coli. The growth of host at low temperature enhanced enzyme in soluble fraction. Similarly, induction of target gene at low level of IPTG also yielded higher enzyme in soluble fraction. The synergistic effect of low temperature and induction on the prevention of inclusion bodies was also evident from our results. In addition, co-expression of the target gene with two types of molecular chaperones (GroESL and KODHsp) was also attempted. However, none of these chaperones enhanced the solubilization under in vivo conditions. Nevertheless, effective role of low growth temperature coupled with low level of induction appeared to be an attractive feature for producing recombinant protein.     

Bioleaching of Heavy Metal Polluted Sediment: Influence of Sediment Properties (Part 2)

A remediation process for heavy metal polluted sediment has previously been developed, in which the heavy metals are removed from the sediment by solid‐bed bioleaching using sulfuric acid as a leaching agent arising from added elemental sulfur (S⁰). This process has been engineered with Weiße Elster River sediment (dredged near Leipzig, Germany), as an example. Here, six heavy metal polluted sediments originating from various bodies of water in Germany were subjected to bioleaching to evaluate the applicability of the developed process on sediment of different nature: each sediment was mixed with 2 % S⁰, suspended in water and then leached under identical conditions. The buffer characteristics of each sediment were mainly governed by its carbonate and Ca content, i.e., by its geological background, the redox potential and oxidation state depended on its pre‐treatment (e.g., on land disposal), while the pH value was influenced by both. The added S⁰ was quickly oxidized by the indigenous microbes even in slightly alkaline sediment. The microbially generated H₂SO₄ accumulated in the aqueous phase and was in part precipitated as gypsum. Significant acidification and heavy metal solubilization only occurred with sediment poor in buffer substances. With the exception of one sediment, the behavior in bioleaching correlated well with the behavior in titration with H₂SO₄. Since the content in carbonate seemed to be the most important factor deciding on the leachability of a sediment, oxic Weiße Elster River sediment was mixed with 2 % S⁰ and 0 to 100 g/kg of ground limestone to simulate various buffer capacities, suspended in water and then leached. The lime did not inhibit microbial S⁰ oxidation but generated a delay in acidification due to neutralization of formed H₂SO₄, where the pH only started to decrease when the lime was completely consumed. The more lime the sediment contained, the longer this lag period lasted, and the higher the pH and the lower the fraction of the solubilized heavy metals finally was. Since Cu requires stronger acidic conditions for its solubilization, it responded more sensitively to lime addition than Zn, Ni, and Cd. Heavy metal polluted sediment containing large amounts of carbonate may, in principle, also be remediated by bioleaching, but metal solubilization requires excessive amounts of the leaching agent and is thus uneconomical.     

Isolation and Characterization of Coal Solubilizing Aerobic Microorganisms from Salt Range Coal Mines,Pakistan

Microbial solubilization of coal has been considered as a promising technology to convert raw coal into valuable products. In the present study, initially a total of 50 different aerobic bacterial and fungal isolates have been isolated from soil, coal and water samples of Dulmial Coal Mines, Chakwal, Pakistan, but on the basis of solubilization potential, only four isolates were selected for further study. The intensity of biosolubilization was measured by determining the weight loss of the coal pieces, which was observed to be about 25.93% by Pseudomonas sp. AY2, 36.36% by Bacillus sp. AY3 and 50% by Trichoderma sp. AY6, while Phanerochaete sp. AY5 showed maximum coal solubilization potential i.e. 66.67% in 30 days. UV/Vis spectrum revealed an increase in the pattern of absorbance of all treated samples compared to control referring to solubilization. Fourier transform infrared spectroscopy indicated alterations in the structure of treated coal in comparison to control coal suggesting breakdown in the complex structure of coal. The major absorbance bands in infrared spectroscopy for solubilization product were attributed to carbonyl (1,600 cm^?1), hydroxyl (3,450 cm^?1), cyclane (2,925 cm^?1), ether linkage (1,000–1,300 cm^?1), carboxyl (3,300–2,500 cm^?1) and side chains of aromatic ring (1,000–500 cm^?1). The presence of microorganisms and surface erosion of coal residues compared to control samples were observed by scanning electron microscopy, which suggested that isolated microorganisms were able to survive in coal for a longer period of time. Therefore, the present study concluded that microorganisms isolated from coal mines have excellent potential for coal solubilization which is considered as a crucial step in coal methanogenesis allowing them to be used successfully for in situ methane production to meet future energy demands.     

Enhancement of Oral Bioavailability of Cilostazol by Forming its Inclusion Complexes

The study was designed to investigate the effect of cyclodextrins (CDs) on the solubility, dissolution rate, and bioavailability of cilostazol by forming inclusion complexes. Natural CDs like β-CD, γ-CD, and the hydrophilic β-CD derivatives, DM-β-CD and HP-β-CD, were used to prepare inclusion complexes with cilostazol. Phase solubility study was carried out and the stability constants were calculated assuming a 1:1 stoichiometry. Solid cilostazol complexes were prepared by coprecipitation and kneading methods and compared with physical mixtures of cilostazol and cyclodextrins. Prepared inclusion complexes were characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry (DSC), and X-ray diffraction (XRD) studies. In vitro dissolution study was performed using phosphate buffer pH 6.4, distilled water, and HCl buffer pH 1.2 as dissolution medium. The optimized inclusion complex was studied for its bioavailability in rabbit and the results were compared with those of pure cilostazol and Pletoz-50. Phase solubility study showed dramatic improvement in the solubility of drug by formation of complexes, which was further increased by pH adjustment. The dissolution rate of cilostazol was markedly augmented by the complexation with DM-β-CD. DSC and XRD curves showed sharp endothermic peaks indicating the reduction in the microcrystallinity of cilostazol. Selected inclusion complex was also stable at ambient temperature up to 6 months. The in vivo study revealed that DM-β-CD increased the bioavailability of cilostazol with low variability in the absorption. Among all cilostazol–cyclodextrins complexes, cilostazol–DM-β-CD inclusion complex (1:3) prepared by coprecipitation method showed 1.53-fold and 4.11-fold increase in absorption along with 2.1-fold and 2.97-fold increase in dissolution rate in comparison with Pletoz-50 and pure cilostazol, respectively.     

High-level expression of a soluble snake venom enzyme,gloshedobin, in E. coli in the presence of metal ions

The mature gene of gloshedobin, a snake venom thrombin-like enzyme from the snake, Gloydius shedaoensis, was cloned and expressed in strain E. coli BL21(DE3). Having been induced by IPTG, the recombinant gloshedobin was in both soluble and insoluble forms. To avoid inclusion body formation, expression was optimized at 25 °C. Furthermore, a 50% increase in solubilization of the target protein was obtained by adding 0.1 mM Mg²⁺ to the medium. The purified recombinant gloshedobin gave a 44 kDa band on SDS-PAGE gel.     

Microbiological Redox Potential Control to Improve the Efficiency of Chalcopyrite Bioleaching

The effect of controlling the redox potential (E_h) on chalcopyrite bioleaching kinetics was studied as a new aspect of redox control during chalcopyrite bioleaching, and its mechanism was investigated by employing the “normalized” solution redox potential (E_normal) and the reaction kinetics model. Different E_h ranges were established by use of different acidophiles (Sulfobacillus acidophilus YTF1; Sulfobacillus sibiricus N1; Acidimicrobium ferrooxidans ICP; Acidiplasma sp. Fv-AP). Cu dissolution was very susceptible to real-time change in E_h during the reaction. It was found that efficiency of bioleaching of chalcopyrite can be effectively evaluated on the basis of E_normal, since it is normalized for real-time fluctuations of concentrations of major metal solutes during bioleaching. For steady Cu solubilization during bioleaching at a maximum rate, it was important to maintain a redox potential range of 0 ≤ E_normal ≤ 1 (?0.35 mV optimal) at the mineral surface by employing a “weak” ion-oxidizer. This led to a copper recovery of > 75%. At higher E_normal levels (E_normal > 1 by “strong” microbial Fe²⁺ oxidation), Cu solubilization was slowed by diffusion through the product film at the mineral surface (< 50% Cu recovery) caused by low reactivity of the chalcopyrite and by secondary passivation of the chalcopyrite surface, mainly by jarosite.     

Over-Expression in <Emphasis Type="Italic">E. coli</Emphasis> and Purification of the Human OCTN2 Transport Protein

The OCTN2 cDNA amplified from human skin fibroblast was cloned in pET-41a(+) carrying the glutathione S-transferase (GST) gene. The construct pET-41a(+)–hOCTN2 was used to express the GST–hOCTN2 fusion protein in Escherichia coli Rosetta(DE3)pLysS. The best over-expression was obtained after 6 h of induction with IPTG at 28°C. The GST–hOCTN2 polypeptide was collected in the inclusion bodies and showed an apparent molecular mass on SDS-PAGE of 85 kDa. After solubilization with a buffer containing 0.8% sarkosyl and 3 M urea, the fusion protein was applied onto a Ni²⁺-chelating chromatography column. The purified GST–hOCTN2 was treated with thrombin, and the hOCTN2 was separated from the GST by size exclusion chromatography. After the whole procedure, a yield of about 0.2 mg purified protein per liter of cell culture was obtained. To improve the protein yield, hOCTN2 cDNA was subjected to codon bias. The second codon CGG was substituted with AAA; the substitution led to the mutation R2K in the hOCTN2 protein. hOCTN2(R2K) cDNA was cloned in pET-21a(+) carrying a C-terminal 6His tag. The resulting protein was expressed in E. coli Rosetta(DE3)pLysS and purified by Ni²⁺-chelating chromatography. A yield of about 3.5 mg purified protein per liter of cell culture was obtained with this procedure.     

Influence of sample preparation technique on two-dimensional gel electrophoresis of proteins from Porphyromonas gingivalis

Sample preparation methods were compared for two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) of cellular proteins from the proteolytic bacterium Porphyromonas gingivalis. Standard solubilization buffer yielded poorly resolved protein spots, but pre-treatment of cells with trichloroacetic acid or inclusion of the protease inhibitor TLCK during solubilization improved definition and separation. The latter approach allowed reliable detection of a 55 kDa immunodominant surface antigen by Western immunoblotting. Further improvements in resolution occurred when SDS was included in the sample preparation. Thus, controlling proteolysis and optimizing protein solubilization were essential for reproducible separations and maximal protein recovery during 2D-PAGE of P. gingivalis.     

Skeletal dissolution kinetics and mechanical tests in response to morphology among coral genera

Ocean acidification is widely accepted as a primary threat to coral reef populations. Negative physiological effects include decreased calcification rates, heightened metabolic energy expenditure, and increased dissolution of coral skeletons. However, studies on the dissolution of coral skeletons structures under ocean acidification conditions and their implications on sediments remain scarce. In this work, we examined skeletal dissolution kinetics from four of the most representative hermatypic corals of the Eastern Pacific coasts (Pocillopora, Porites, Pavona, and Psammocora). Samples were treated with a highly acidic solution for defined periods of time, and measurements of dissolved calcium ([Ca⁺²]) were used to evaluate the kinetics of coral skeleton dissolution. All genera tests except Porites showed a zero reaction rate. Porites exhibited a first-order reaction and a faster reaction rate than other genera. Compression strength tests and skeletal density did not correlate with reaction rate. Pavona showed greater structural strength. Porites were the most susceptible to acidic dissolution compared to other genera tested due to their morphology, i.e., possession of the largest surface area, suggesting a high vulnerability under low-pH conditions. The hierarchical response in dissolution kinetics among coral genera tested suggests that the most soluble coral might act as a buffer under ocean acidification conditions.