pH Control Research Articles

Modeling, simulations, and Simulink developments in the analysis of optimal control of temperature and pH in a batch ethanol fermentation process

Transfer of laboratory-scale experiments to production-scale ethanol fermentation is time-consuming and involves expensive prototype systems from complex experimental designs that determine optimal operating conditions for minimal substrate and product inhibitions. The study developed and validated a Simulink-based model for optimal pH and temperature control using fuzzy logic and PID controllers respectively and taking advantage of 2D and 1D substrate and product inhibition models from which suitable ethanol fermentation reaction rates models were selected. Temperature and pH levels and substrate, product, and biomass concentrations were measured. Selected inhibition models were linear-product, linear substrate-sudden stop product, and linear substrate for cassava, maize, and sorghum, respectively. Fuzzy logic controller ascertained optimal flow rate of acid and base as 0.000196 ml/s and 0.000204 ml/s, respectively, and pH error and rate of pH error as 0.00334 and 0.00368, respectively. F-test two-sample for variances showed no significant difference between model and experimental curves (cassava: F critical = 0.9704, F calculated = 0.1905; maize: F critical 0.9704, F calculated = 0.2149; sorghum: F critical = 0.9704, F calculated = 0.2488). PID logic controller showed model curves and experimental curves with good fit. F-test two-sample for variances showed no significant difference between model and experimental curves (cassava: F critical = 0.9704, F calculated = 0.1288; maize: F critical = 0.9704, F calculated = 0.2083; sorghum: F critical = 0.9704, F calculated = 0.2016). The study provided an improved approach as solution for optimal pH and temperature conditions in order to mitigate substrate and product inhibitions during ethanol fermentation. It illustrated that the application of artificial intelligence-based controllers provides satisfactory outcomes that are desirable for implementation in the industrial space.Graphical

Encapsulation of a drug into electrospun fibers spun from water soluble polymers to control solubility and release

Electrospun fibers prepared from water-soluble polymers (PVP, PVA, and HPMC) were loaded with pregabalin, a BCS I drug, to address its fast release and adverse effects. The drug dissolved partially (1.8–2.8 wt%) in the polymers, with excess pregabalin in crystalline form within the fibers. The solubility of the drug varied with the pH of the dissolution medium. Most of the drug encapsulated into the fibers during electrospinning, but some was lost due to technical reasons. PVP showed no impact on drug release, offering no benefit as a carrier. However, PVA-based fibers exhibited considerably slower release than the dissolution rate of the neat drug and also the release rate from fibers prepared from the other polymers. This indicates the potential of PVA for using it with pregabalin in practical drug formulations with improved release properties. The pH of the dissolution medium influenced solubility and release rate for specific polymers. Overall, the study highlights the importance of polymer selection and pH control in optimizing the release profile of pregabalin in enhanced drug delivery.

Mechanism of pyrite depression by marine Fe(II)-oxidizing bacteria in seawater flotation

Seawater flotation is a promising technique to reduce environmental and economic loads in mineral processing. This study attempted to depress pyrite, a common gangue sulfide mineral, using two marine iron (Fe) oxidizing bacteria (MFeOB), Thalassospira sp. TF-1 and Mariprofundus sp. E-4, in seawater flotation without pH control; the MFeOB could contribute to hydrophilization of the pyrite surface by oxidation and/or adhesion of bacterial cells. Pyrite or chalcopyrite samples were preconditioned in seawater containing MFeOB for different times (15 min or 30 min). As a result of flotation experiments, the recovery of pyrite preconditioned without MFeOB (i.e., control sample) decreased to 64.2 % after 30 min reaction. The same recovery was observed when pyrite was preconditioned with Thalassospira sp. TF-1, whereas the recovery was successfully decreased to 20.2 % after preconditioning with Mariprofundus sp. E-4 for 30 min. X-ray photoelectron spectroscopy analysis of preconditioned pyrite samples showed no significant difference of Fe-oxidizing compounds between with and without MFeOB reaction, suggesting that the formation of hydrophilic substances such as Fe(OH)3 derived from pyrite oxidation by MFeOB is unlikely to be the main reason for the pyrite depression by Mariprofundus sp. E-4. The adhesion experiment revealed that MFeOB cells could cover the pyrite surface but not the chalcopyrite surface, showing that the hydrophilicity of Mariprofundus sp. E-4 cell caused the pyrite depression. This result suggests that the hydrophilic/hydrophobic properties of bacterial cells are a significant determining factor in pyrite recovery in seawater flotation in the case of MFeOB.

A method for suppressing pH excursion during elution in ion-exchange chromatography

A simple method for reducing pH excursion during salt-induced elution in cation exchange chromatography is presented in this paper. Connecting a preequilibrated anion exchange cartridge in series in front of the cation exchange device just prior to the elution step significantly reduced the transient decrease in pH that is typically observed during elution. The working principle of the proposed method is hypothesized. Bind and elute chromatography experiments showed that the suppression of pH excursion during elution of a monoclonal antibody from a cation exchange chromatography device resulted in significantly sharper and narrower eluted protein peaks. Improvement in pH control during elution would not only result in better reproducibility and efficiency in separation but would also ensure greater stability of pH sensitive proteins during their purification using ion exchange chromatography.

Engineering ethanologenicity into the extremely thermophilic bacterium Anaerocellum (f. Caldicellulosiriuptor) bescii

The anaerobic bacterium Anaerocellum (f. Caldicellulosiruptor) bescii natively ferments the carbohydrate content of plant biomass (including microcrystalline cellulose) into predominantly acetate, H2, and CO2, and smaller amounts of lactate, alanine and valine. While this extreme thermophile (growth Topt 78 °C) is not natively ethanologenic, it has been previously metabolically engineered with this property, albeit initially yielding low solvent titers (∼15 mM). Herein we report significant progress on improving ethanologenicity in A. bescii, such that titers above 130 mM have now been achieved, while concomitantly improving selectivity by minimizing acetate formation. Metabolic engineering progress has benefited from improved molecular genetic tools and better understanding of A. bescii growth physiology. Heterologous expression of a mutated thermophilic alcohol dehydrogenase (AdhE) modified for co-factor requirement, coupled with bioreactor operation strategies related to pH control, have been key to enhanced ethanol generation and fermentation product specificity. Insights gained from metabolic modeling of A. bescii set the stage for its further improvement as a metabolic engineering platform.

Synergistic mechanism of pH control by CO2 and CaO2 pre-oxidation to enhance algae dehydration

This study investigated the improvement of algal dehydration efficiency through CO2 pH adjustment and moderate pre-oxidation with CaO2 to enhance coagulation. Adjusting the pH of algal water to 6.0–9.5 with CO2 significantly affected zeta potential and photosynthesis, enhancing aluminum hydrolysis product aggregation. At pH 6.5, the composition of algal organic matter closely matched the original water, indicating minimal impact on algae and optimal cell activity. CaO2 pre-oxidation effectively reduced residual aluminum content and DOM release after coagulation. The DOM removal rate reached 44.50 % at pH 6.5, with the highest dehydration efficiency of 44.34 % and the lowest cell rupture rate of 5.55 %. Small molecular aromatic proteins decreased, while humic substances increased significantly. The chemical bonding between the EPS membrane and CaO2 improved system density and elasticity, enhancing dehydration performance. This study provides new insights and guidance for the ongoing study of pH and CaO2 enhanced algal dehydration.

Cascading Macrocycle and Helix Motions in a Foldarotaxane Molecular Shuttle.

The design of a dynamically assembled foldarotaxane was envisioned with the aim of operating as a two cascading triggers-based molecular shuttle. In acidic conditions, both the macrocycle and helix were localized around their respective best molecular stations because they are far enough from each other not to alter the stability of complexes. The pH-dependent localization of the macrocycle along the encircled axle allowed us to modulate the association between the helical foldamer and its sites of interaction on the axle. Under kinetic control,at low concentration and room temperature,when the foldarotaxane supramolecular architecture is kinetically stable, the pH-responsive translation of the macrocycle along the thread triggered the gliding of the helix away from its initial best station. At higher concentration,when helix assembly/disassembly process is accelerated,the system reached the equilibrium state. A new foldarotaxane isomer then appeared through the change of the relative position of the helix and macrocycle along the thread. In this isomer, the helix segregated the macrocycle away from its best station. The fine control of the kinetic and thermodynamic processes, combined with the control of pH, allowed the reciprocal segregation of the helix or the ring away from their respective best sites of interaction.

Cascading Macrocycle and Helix Motions in a Foldarotaxane Molecular Shuttle

The design of a dynamically assembled foldarotaxane was envisioned with the aim of operating as a two cascading triggers‐based molecular shuttle. In acidic conditions, both the macrocycle and helix were localized around their respective best molecular stations because they are far enough from each other not to alter the stability of complexes. The pH‐dependent localization of the macrocycle along the encircled axle allowed us to modulate the association between the helical foldamer and its sites of interaction on the axle. Under kinetic control, at low concentration and room temperature, when the foldarotaxane supramolecular architecture is kinetically stable, the pH‐responsive translation of the macrocycle along the thread triggered the gliding of the helix away from its initial best station. At higher concentration, when helix assembly/disassembly process is accelerated, the system reached the equilibrium state. A new foldarotaxane isomer then appeared through the change of the relative position of the helix and macrocycle along the thread. In this isomer, the helix segregated the macrocycle away from its best station. The fine control of the kinetic and thermodynamic processes, combined with the control of pH, allowed the reciprocal segregation of the helix or the ring away from their respective best sites of interaction.

Decoupling Charge Carrier Electroreduction and Enzymatic CO2 Conversion to Formate Using a Dual-Cell Flow Reactor System.

With an efficient atom economy, low activation energy, and valuable applications for fuel cells and hydrogen storage, formic acid (FA) is a useful fuel product to convert CO2 and reduce emissions. Although metal catalysts are typically used for this conversion, unwanted side reactions remain a concern, particularly when products are attempted to be recovered long-term. In this study, an enzymatic catalyst is used to enable the selective conversion of CO2 to FA, as a formate ion. A dual-cell flow reactor system is used to first reduce a charge mediator electrochemically (reduction cell), which then activates a catalyst to selectively convert CO2 to formate (production cell). This approach minimizes enzyme degradation by avoiding direct contact with increased voltages and improves the quantity of formate produced. The system produced 25 mM of formate and reached over 50% Coulombic efficiency. The larger volume of this dual-cell system increases the quantity of formate produced beyond that of a batch cell. Additional design configurations are employed, including a pH control pump to maintain catalyst activity and a packed bed reactor to improve contact of the charge carrier with the catalyst. Both configurations retained higher production and efficiency long-term (∼168 h). The results highlight the challenges of developing a system where many parameters play a role in optimizing performance. Nevertheless, the ability of the system to produce formate from CO2 demonstrates the potential to improve upon this configuration for a variety of electrochemical CO2 conversion applications.

The Valorization of Fruit and Vegetable Wastes Using an Anaerobic Fixed Biofilm Reactor: A Case of Discarded Tomatoes from a Traditional Market

Tomato waste, characterized by high organic matter and moisture content, offers a promising substrate for anaerobic digestion, though rapid acidification can inhibit methanogenic activity. This study investigated the performance of a 10.25 L anaerobic fixed biofilm reactor for biogas production using liquid tomato waste, processed through grinding and filtration, at high organic loading rates, without external pH control or co-digestion. Four scouring pads were vertically installed as a fixed bed within a fiberglass structure. Reactor performance and buffering capacity were assessed over three stages with progressively increasing organic loading rates (3.2, 4.35, and 6.26 gCOD/L·d). Methane yields of 0.419 LCH4/gCOD and 0.563 LCH4/g VS were achieved during the kinetic study following stabilization. Biogas production rates reached 1586 mL/h, 1804 mL/h, and 4117 mL/h across the three stages, with methane contents of 69%, 65%, and 72.3%, respectively. Partial alkalinity fluctuated, starting above 1500 mg CaCO3/L in Stage 1, dropping below 500 mg CaCO3/L in Stage 2, and surpassing 3000 mg CaCO3/L in Stage 3. Despite periods of forced acidification, the system demonstrated significant resilience and high buffering capacity, maintaining stability through hydraulic retention time adjustments without the need for external pH regulation. The key stability indicators identified include partial alkalinity, effluent chemical oxygen demand, pH, and one-day cumulative biogas. This study highlights the effectiveness of anaerobic fixed biofilm reactors in treating tomato waste and similar fruit and vegetable residues for sustainable biogas production.

In-Situ Product Removal for the Enzymatic Depolymerization of Poly(ethylene terephthalate) via a Membrane Reactor.

Poly(ethylene terephthalate) (PET) is a common single-use plastic and a major contributor to plastic waste. PET upcycling through enzymatic depolymerization has drawn significant interests, but lack of robust enzymes in acidic environments remains a challenge. This study investigates in-situ product removal (ISPR) of protons from enzymatic PET depolymerization via a membrane reactor, focusing on the ICCG variant of leaf branch compost cutinase. More than two-fold improvements in overall PET depolymerization and terephthalic acid yields were achieved employing ISPR for an initial PET loading of 10 mgPET mlbuffer-1. The benefit of ISPR was reduced for a lower initial loading of 1 mgPET mlbuffer-1 due to decreased need for pH stabilization of the enzyme-containing solutions. A back-of-envelop analysis suggests that at a modest dilution ratio, ISPR could help achieve savings on caustic base solutions used for pH control in a bioreactor. Our study provides valuable insights for future ISPR developments for enzymatic PET depolymerization, addressing the pressing need for more sustainable solutions towards plastic recycling and environmental conservation.

Insights into the crucial role of pH to achieve the dual goals of efficient fluoride removal and resource recovery from the photovoltaic manufacturing wastewater

Fluoride-containing wastewater arose from the rapid development of photovoltaic manufacturing, and caused many environmental and health concerns. Chemical precipitation is commonly applied for fluoride removal, in which pH plays a crucial role while lacking systematic and in-depth research. In this study, the effect of pH on fluoride removal was investigated from both theoretical and experimental views, and the recovered precipitates with pH control were characterized. Theoretical analysis illustrated the quantitative relationship between reaction rate and pH, which indicated an optimal pH of about 8 for fluoride removal. This result was further validated by the batch and continuous experiments. In the batch experiments, the highest fluoride removal efficiency of 99.00 ± 0.01 % and lowest fluoride residual of 19.93 ± 0.16 mg/L were achieved at pH 8.00. In the continuous experiments, the fluoride residual was controlled under 10 mg/L with a fluoride removal rate of 2298.3 ± 0.5 kg F/(m3·d) in the optimal pH range of 6.95 to 8.47. The precipitate characteristics in terms of morphology, elements composition, and crystallization property showed a close correlation with reaction pH. Furthermore, a multidimensional system involving CaF2 content, precipitant saving, particle size, crystallinity, and fluoride residual was established to assess the fluoride removal and precipitate recovery with pH control. A neutral condition was recommended to achieve the above dual goals. This work provided systematical and deep insights into the pH role in fluoride removal and precipitates recovery, and could offer guidelines for the development of industrial fluoride-containing wastewater treatment.

Influence of pH on the Stability of Pharmaceutical Compounds in Japan

Purpose: The aim of the study was to assess the influence of pH on the stability of pharmaceutical compounds in Japan. Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: The study showed that the ionization state of a drug molecule can change with pH, leading to different degradation pathways. Acidic or basic conditions can catalyze hydrolysis, oxidation, and other chemical reactions, causing the drug to lose potency or form harmful by-products. For instance, ester and amide bonds in pharmaceuticals are prone to hydrolysis at extreme pH levels, while oxidative degradation is more prevalent at neutral or slightly basic pH. The stability of certain antibiotics, vitamins, and biologics is particularly pH-sensitive, necessitating careful formulation to maintain optimal pH levels. Buffer systems are often employed to stabilize the pH within a range that minimizes degradation. Additionally, the pH of the solution can influence the solubility and bioavailability of the drug, impacting its therapeutic efficacy. Thus, understanding and controlling the pH environment is crucial in pharmaceutical formulation to ensure drug stability, efficacy, and safety throughout its shelf life. Implications to Theory, Practice and Policy: Buffer theory, Arrhenius theory of acid-base reactions and Bronsted Lowry theory may be used to anchor future studies on assessing the influence of pH on the stability of pharmaceutical compounds in Japan. Practically, it is imperative for pharmaceutical companies to implement rigorous pH control in the formulation and storage of drugs. On a policy level, regulatory agencies should establish stringent guidelines for the pH stability of pharmaceutical compounds.

Validation of an Optical Technology for the Determination of pH in Milk during Yogurt Manufacture.

Current systems that allow inline pH control in the fermented dairy industry have drawbacks, such as protein adhesion on the non-glass pH probes, measurement distortion, frequent recalibration needs, and sensitivity to extreme pH conditions encountered during clean-in-place operations. Therefore, the objective of this study was to validate the feasibility of estimating the pH of milk during the yogurt making process by using a NIR light backscatter sensor measuring under different fermentation temperatures and milk protein concentrations using a mathematical model that correlates the light scatter signal with pH. Three replications of the experiment with two protein concentrations (3.5 and 4.0%) and two fermentation temperatures (43 and 46 °C) were used to validate this inline pH prediction model. Continuous and discontinuous measurements of pH were collected as a reference during fermentation, simultaneously with the light backscatter data acquisition. Also, the effect of adjusting the initial voltage gain of the light scatter device on the accuracy of the pH prediction model was evaluated. Temperature and initial voltage were the main factors affecting the fitting accuracy of the model. The adjustment of the initial voltage gain improved the pH prediction model fit. The model has been successfully validated for both continuous and discontinuous measurements of pH, with SEP values < 0.09 pH units and CV < 1.78%. The proposed optical inline and non-destructive method was feasible for inline pH monitoring of milk fermentation, avoiding traditional manual pH measurement.

Highly Reversible "On-Off-On" Fluorescence Switch Governed by pH, Utilizing Bis(Benzimidazole) Derivatives with Varied Link Groups.

In this work, a series of dibenzimidazole derivatives 1-4, act as highly reversible colorimetric and fluorescent pH chemosensor, were designed and synthesized. Excellent reversible pH response of these sensors could be found by a specific pH change through obvious fluorescent color changes. The response is not affected by common cations (including Al3+, Cu2+, Ca2+, Cd2+, Co2+, Cr3+, Mg2+, Na+, K+, Ni2+, Pb2+ and Zn2+) and anions (including F-, Cl-, Br-, I-, ClO4-, H2PO4-, HSO4-, HCO3- and CH3COO-). Notably, these sensors can be reused more than 10 times without losing functionality. Unlike previous reports, the distinct properties of 1-4 are attributed to the varied link groups. Based on comprehensive experimental data and mechanistic analyses, it is concluded that sensors 1-4 are promising candidates for use as highly reversible "on-off-on" fluorescence switches under precise pH control.

Enhancing levan biosynthesis by destroying the strongly acidic environment caused by membrane-bound glucose dehydrogenase (mGDH) in Gluconobacter sp. MP2116

Levan produced by Gluconobacter spp. has great potential in biotechnological applications. However, Gluconobacter spp. can synthesize organic acids during fermentation, resulting in environmental acidification. Few studies have focused on the effects of environmental acidification on levan synthesis. This study revealed that the organic acids, mainly gluconic acid (GA) and 2-keto-gluconic acid (2KGA) secreted by Gluconobacter sp. MP2116 created a highly acidic environment (pH < 3) that inhibited levan biosynthesis. The levansucrase derived from strain MP2116 had high enzyme activity at pH 4.0 ∼ pH 6.5. When the ambient pH was less than 3, the enzyme activity decreased by 67 %. Knocking out the mgdh gene of membrane-bound glucose dehydrogenase (mGDH) in the GA and 2KGA synthesis pathway in strain MP2116 eliminated the inhibitory effect of high acid levels on levansucrase function. As a result, the levan yield increased from 7.4 g/l (wild-type) to 18.8 g/l (Δmgdh) during fermentation without pH control. This study provides a new strategy for improving levan production by preventing the inhibition of polysaccharide synthesis by environmental acidification.

New insight into process pH regulation on caproate production from waste activated sludge acidogenic fermentation liquid by cathodic electro-fermentation

Cathodic electro-fermentation (CEF) has been proven to enhance the production of caproate from biowaste by improving chain elongation metabolism. However, the impact of process pH control in catholyte to avoid pH changes caused by redox reactions under polarized cathode on chain elongation has been rarely reported. Here the caproate production performances from waste activated sludge acidogenic fermentation liquid were evaluated and compared between different process pHs of 5.5, 6.0, and 6.5 with control group at 0.9 V. Results demonstrated the maximum caproate concentration was reached 4.1 g/L at pH 6.0, which was significantly higher than the 2.7 g/L of the control group, indicating the benefits of pH control on chain elongation metabolism in CEF. Mechanisms analysis revealed that the enhancement of pH regulation was attributed to the enrichment of organic degraders (Pseudomonas) in catholyte and the increased metabolic activity (like acetyl-CoA carboxylase) of chain elongator (Clostridium_sensus_stricto_12) on biofilm. These results were evidenced by the improved release and conversion performance of substrates (especially the amino acids) in catholyte and the enhanced biofilm activity. Hence, this study contributes novel insights to the pH regulation of chain elongation for enhancing caproate production from biowaste by electro-fermentation.

Utilizing Advanced Bipolar Membranes in Next Generation Electrodialysis Systems

Bipolar membranes (BPMs) have experienced a renaissance, owing to their proposed use in membrane electrode assembly (MEA) systems. MEA systems encompass technologies such as fuel cells and electrolyzers, where the BPM allows for fine pH control at the electrodes and helps to prevent ion-crossover that may lead to lower system efficiencies and fouling of the system. The exploration of MEA systems has significantly expanded our fundamental understanding of BPM functionality and limits, setting the stage for future advancements in BPM applications.Beyond MEA systems, BPMs have been seen in a wide array of technologies such as CO2 sequestration systems, electrodialysis, brine remediation, organic acid/base production, and more. These applications all present unique stressor to the BPM that prevent the direct translation of advanced, MEA optimized BPM to these non-MEA systems. Initial investigations into transferring advanced BPM to non-MEA applications have found issues with membrane delamination at scale and a need for system specific catalyst optimization. However, the fundamentals learned from MEA systems translate well and can be used to inform advancements of BPM in these non-MEA systems. Here we present initial findings and proposed solutions for durability issues when optimizing advanced BPM for application in BPM electrodialysis.

Production of Volatile Fatty Acids from Cheese Whey and Their Recovery Using Gas-Permeable Membranes

The use of anaerobic fermentation to produce volatile fatty acids (VFAs) is an environmentally sustainable alternative for cheese whey (CW) valorization. This study evaluates the effect of pH control on the conversion of organic matter to VFAs from CW and assesses VFA recovery using a novel approach based on gas-permeable membranes. VFA bioconversion and composition were studied with initial and sequential control of pH, both in acidic and alkaline conditions. Bioconversion efficiencies for assays with initial pH control were 36% and 45% for acidic and alkaline conditions, respectively. Sequential control of pH resulted in an increase in bioconversion to 54% under acidic conditions. Under acidic conditions, a variety of VFA was produced (mainly butyric, acetic, and propionic acids), while under alkaline conditions the majority was acetic acid. VFA recovery using a novel system of tubular gas-permeable membranes accounted for 15% and 100% of the total VFA from effluent 1 (butyric, acetic, and propionic acids) and effluent 2 (mainly acetic acid), respectively.

Chemical gasification: An alternative approach to invitro maturation of bovine oocytes.

This study aimed to evaluate the effect of chemical gasification and HEPES as alternative systems to pH control during invitro maturation on bovine oocytes competence. Groups of 20 bovine cumulus oocytes complexes (COCs) were randomly distributed and cultured for 24 h in one of the following experimental groups: (i) chemical reaction (ChRG) system: CO2 generated from sodium bicarbonate and citric acid reaction (ii) culture media TCM-HEPES (HEPES-G); and (iii) control group (CNTG) in conventional incubator. After invitro maturation (IVM), the COCs were invitro fertilized (IVF), and invitro cultivated (IVC) in a conventional incubator. We evaluated oocyte nuclear maturation, cleavage and blastocyst rates, in addition to the relative mRNA expression of BAX, BMP-15, AREG and EREG genes in oocytes and cumulus cells. The proportion of oocytes in metaphase II was higher in CNTG and ChRG (77.57% and 77.06%) than in the HEPES-G (65.32%; p = .0408 and .0492, respectively). The blastocyst production was similar between CNTG and ChRG (26.20% and 28.47%; p = .4232) and lower (p = .001) in the HEPES-G (18.71%). The relative mRNA expression of BAX gene in cumulus cells was significantly higher (p = .0190) in the HEPES-G compared to the CNTG. Additionally, the relative mRNA expression of BMP-15 gene was lower (p = .03) in oocytes from HEPES-G compared to the CNTG. In conclusion, inadequate atmosphere control has a detrimental effect on oocyte maturation. Yet, the use of chemical gasification can be an efficient alternative to bovine COCs cultivation.