Effect Of pH Changes Research Articles

The Effect of the Acid-Base Imbalance on the Shape and Structure of Red Blood Cells.

Red blood cells respond to fluctuations in blood plasma pH by changing the rate of biochemical and physical processes that affect the specific functions of individual cells. This study aimed to analyze the effect of pH changes on red blood cell morphology and structure. The findings revealed that an increase or decrease in pH above or below the physiological level of pH 7.4 results in the transformation of discocytes into echinocytes and causes significant alterations in the membrane, including its roughness, cytoskeleton structure, and the cell's elastic modulus. Furthermore, the study shown a strong connection between critical acidosis and alkalosis with increased intracellular reactive oxygen species production.

Potential effects of pH changes in the micro-environment during desalination on infant powder: The perspective of pH shift affecting whey protein molecular structure and function

In order to simulate the effect of pH environment change caused by different desalting methods on whey protein (WP) in actual production, the WP was treated under different acidic pH (2.0–6.0) and pH shift (pH recovery). The molecular structure, properties, and functions of the proteins were further analyzed. The results showed that the spatial structure of WP was unfolded under acidic conditions, α-helix and β-sheet were transformed into random coils, hydrophobic residues and free sulfhydryl groups were exposed. The particle size of WP was increased, and the emulsification, foaming and thermal stability were improved significantly. Especially after pH2 treatment, WP has the largest expansion degree, emulsification and foaming properties increased to 232.96 m2/g and 158.83 %. After pH recovery, the partially unfolded structure refolded, reducing the surface hydrophobicity, forming a smaller particle size of soluble protein particles, solubility has increased to 83.95 % compared to the natural. However, the emulsification, foamability, and thermal stability after pH shift are slightly reduced compared to acidic conditions, making it easier to form a gel after heating.

Differential Cytoophidium Assembly between Saccharomyces cerevisiae and Schizosaccharomyces pombe.

The de novo synthesis of cytidine 5'-triphosphate (CTP) is catalyzed by the enzyme CTP synthase (CTPS), which is known to form cytoophidia across all three domains of life. In this study, we use the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe as model organisms to compare cytoophidium assembly under external environmental and intracellular CTPS alterations. We observe that under low and high temperature conditions, cytoophidia in fission yeast gradually disassemble, while cytoophidia in budding yeast remain unaffected. The effect of pH changes on cytoophidia maintenance in the two yeast species is different. When cultured in the yeast-saturated cultured medium, cytoophidia in fission yeast disassemble, while cytoophidia in budding yeast gradually form. Overexpression of CTPS results in the presence and maintenance of cytoophidia in both yeast species from the log phase to the stationary phase. In summary, our results demonstrate differential cytoophidium assembly between Saccharomyces cerevisiae and Schizosaccharomyces pombe, the two most studied yeast species.

Impact of non-covalent interactions on the solvation of ovalbumin in an aqueous environment of different pHs: Thermodynamic and diffusion studies

The solvation behavior of protein is an important factor in protein-based food products. In the present study, the xylitol (XY) - ovalbumin (OVN) interaction in an aqueous solution of different pH conditions is analyzed in two methods. In one method, the thermodynamic parameters Gibbs free energy, free volume, and internal pressure are calculated by using ultrasonic velocity, density, and viscosity in addition the refractive index is also measured. The second method is a theoretical method in which using the Laplace transform technique the diffused amount of protein have been calculated for OVN with and without XY in different pH environment. The addition of XY with OVN makes the system with more free energy and free volume as the internal pressure decreases. This trend shows that preferential interaction occurs between solvent–solute molecules. The diffusivity of OVN is reduced after the addition of XY representing the strength of protein-protein interaction. The effect of pH changes is well reflected in both experimental and theoretical results. The results confirm that acidic pH extremity offers more solvation of OVN compared to alkaline pH extremity.

Effects of pH Changes on Phytoplankton Biomass

A phytoplankton was incubated for a week to determine the effects of pH changes on its biomass growth in nutrient enrichment incubation samples. In this experiment, a general increase in phytoplankton biomass was observed after 24 hours of incubation, with a similar growth pattern in all incubation samples. By comparing with the same pH range (7.0 to 8.0), Pulau Pangkor (PP) incubation samples achieved the peaks earlier compared to Pulau Redang (PR) samples, although they had a higher increment in biomass. Meanwhile, in extreme pH (4.0 and 9.0) incubation samples, the phytoplankton biomass was observed to thrive well. This present study suggests that the phytoplankton community in Pulau Redang and Pulau Pangkor waters is able to survive in a wide range of pH levels, and the change in ocean pH has no vital impacts on the phytoplankton based on the short-term experiment.

Application of a new MDCKII-MDR1 cell model to measure the extent of drug distribution in vitro at equilibrium for prediction of in vivo unbound brain-to-plasma drug distribution

Intro: Reliable estimates of drug uptake from blood to brain parenchyma are crucial in CNS drug discovery and development. While in vivo Kp,uu,brain estimates are the gold standard for investigating brain drug disposition, animal usage is a limitation to high throughput application. This study investigates an in vitro model using P-gp expressing MDCKII-MDR1 cells for predicting in vivo brain drug penetration. Methods: In vitro equilibrium distribution studies were conducted in apical and basolateral solutions with high protein content to estimate Kp,brain and Kp,uu,brain values. The correlation between in vitro and in vivo Kp,brain values for a set of compounds was examined. Results: We observed a good correlation between in vitro and in vivo Kp,brain values (R2 = 0.69, Slope: 1.6), indicating that the in vitro model could predict in vivo drug brain penetration. The ‘unilateral (Uni-L)’ in vitro setup correctly classified 5 out of 5 unrestricted compounds and 3 out of 5 restricted compounds. Possible reasons for the observed disparities for some compounds have been discussed, such as difference in transport areas between in vitro and in vivo settings and effect of pH changes. Conclusion: The in vitro assay setup developed in this study holds promise for predicting in vivo drug brain penetration in CNS drug discovery. The correlation between in vitro and in vivo Kp,brain values, underscores that the model may have potential for early-stage screening. With minor refinements, this in vitro approach could reduce the reliance on in vivo experiments, accelerating the pace of CNS drug discovery and promoting a more ethical research approach.

Physicochemical and Emulsifying Properties of Melia azedarach Gum.

Naturally occurring hydrophilic colloids are versatile excipients in drug delivery systems. They are often used as coating materials, disintegrating agents, binders, emulsion stabilizers, and other applications. This study sought to investigate the physicochemical and emulsifying properties of gum extracted from Melia azedarach (MA). The gum was harvested, authenticated, and purified using ethanol precipitation. Physicochemical, microbial, and proximate analyses were performed on the purified gum. Oil of olive emulsions containing different amounts (5-15%w/v) of the gum as emulsifiers were prepared by homogenization. The zeta potential, creaming index, and average droplet size of products were assessed. The effects of pH changes, temperature, and monovalent and divalent electrolytes on the stability of the emulsions were also investigated. The yield of the gum after purification was 68.3%w/w. The gum has low moisture content and good swelling properties. Lead, copper, cadmium, and mercury were not detected. Emulsions containing 15%w/v of acacia or MA gum had the smallest average (Z-average) droplet size (acacia: 1.837 ± 0.420 μm; MA gum: 2.791 ± 0.694 μm) and the highest zeta potential (acacia: -30.45 mV; MA gum: -32.867 mV). Increasing the concentration of the gums increased the emulsion viscosity with MA gum emulsions being more viscous than corresponding acacia emulsions. MA gum emulsions had higher emulsion capacity and stability but lower creaming index relative to acacia gum emulsions of similar concentrations. Potassium chloride (KCl) reduced zeta potential but increased Z-average for emulsions prepared with either gum. Calcium chloride (CaCl2) produced a similar but more pronounced effect. When the pH was decreased from 10 to 2, the zeta potential of the droplets was reduced, but the droplet size of emulsions prepared from either gum was increased. Increasing temperature from 25 to 90°C produced no significant (p value >0.9999) change in droplet size. These findings suggest that MA gum is a capable emulsifying agent at 15%w/v.

Redox regulation in chloroplast thylakoid lumen: The pmf changes everything, again.

Photosynthesis is the foundation of life on Earth. However, if not well regulated, it can also generate excessive reactive oxygen species (ROS), which can cause photodamage. Regulation of photosynthesis is highly dynamic, responding to both environmental and metabolic cues, and occurs at many levels, from light capture to energy storage and metabolic processes. One general mechanism of regulation involves the reversible oxidation and reduction of protein thiol groups, which can affect the activity of enzymes and the stability of proteins. Such redox regulation has been well studied in stromal enzymes, but more recently, evidence has emerged of redox control of thylakoid lumenal enzymes. This review/hypothesis paper summarizes the latest research and discusses several open questions and challenges to achieving effective redox control in the lumen, focusing on the distinct environments and regulatory components of the thylakoid lumen, including the need to transport electrons across the thylakoid membrane, the effects of pH changes by the proton motive force (pmf) in the stromal and lumenal compartments, and the observed differences in redox states. These constraints suggest that activated oxygen species are likely to be major regulatory contributors to lumenal thiol redox regulation, with key components and processes yet to be discovered.

The Development of a Novel Aflibercept Formulation for Ocular Delivery

Aflibercept is a recombinant fusion protein that is commercially available for several ocular diseases impacting millions of people worldwide. Here, we use a case study approach to examine alternative liquid formulations for aflibercept for ocular delivery, utilizing different stabilizers, buffering agents, and surfactants with the goal of improving the thermostability to allow for limited storage outside the cold chain. The formulations were developed by studying the effects of pH changes, substituting amino acids for sucrose and salt, and using polysorbate 80 or poloxamer 188 instead of polysorbate 20. A formulation containing acetate, proline, and poloxamer 188 had lower rates of aggregate formation at 4, 30, and 40°C when compared to the marketed commercial formulation containing phosphate, sucrose, sodium chloride, and polysorbate 20. Further studies examining subvisible particles after exposure to a transport stress and long-term stability at 4°C, post-translational modifications by multi-attribute method, purity by reduced and non-reduced capillary electrophoresis, and potency by cell proliferation also demonstrated a comparable or improved stability for the enhanced formulation of acetate, proline, and poloxamer 188. This enhanced stability could enable limited storage outside of the cold chain, allowing for easier distribution in low to middle income countries.

Influences of changes in pH, temperature, and particle size on surface reaction resistance and diffusion resistance in the struvite dissolution process

Struvite (MgNH4PO4·6 H2O，MAP), a type of high-quality, slow-release fertilizer, is the main component of urinary stones in animals and humans and causes scale formation in industrial pipes. Therefore, MAP dissolution is an important research topic. Herein, MAP dissolution experiments are performed and a thermodynamic model is developed to evaluate the influences of pH, temperature (T), and particle size (Ps) on surface reaction resistance (1/ks) and diffusion resistance (1/kd). The results show that MAP solubility decreases with an increase in pH and the effects of pH change are more obvious than those of T or Ps. The total resistance (1/kT) of MAP dissolution increases with pH increase, Ps growth, or T reduction. The comparison of 1/ks and1/kd reveals surface reaction as the MAP dissolution control step and indicates a linear relation among 1/ks, 1/kd, and the natural logarithm of Ps at pH 7.0.

Tumor‐pH‐value responsive non‐peripheral substituted phthalocyanines: Synthesis, investigation of photophysical and photochemical properties

Cancer is one of the diseases with the highest mortality rate worldwide. Although PDT has recently produced encouraging outcomes, there are still many areas that need to be improved. The first of these is the negative consequences faced by patients treated with the PDT method when exposed to sunlight. For this reason, a new PDT method has been developed in recent years, and it is aimed at using photosensitizer molecules that can be active in acidic conditions. Since the pH values of tumor tissues are more acidic than normal tissues, preparing molecules that act effectively in acidic conditions will allow for more effective results in treating cancer with PDT. In this context, within the scope of this study, 3‐(4‐propionylphenoxy)phthalonitrile (1) and its non‐peripheral tetra‐substituted phthalocyanine derivatives [(2), (3), and (4)] were prepared. With these phthalocyanine derivatives, the novel compounds (5), (6), and (7) were synthesized for the first time. The aggregation tendencies of newly synthesized phthalocyanines (5–7) were investigated in solvent media. The effects of pH changes upon UV–Vis and fluorescence spectra were performed. The electronic and emission spectra of synthesized phthalocyanine derivatives are highly sensitive to pH changes. Formation constant (LogK) values of mono‐ and di‐protonated phthalocyanine forms were calculated by the Henderson–Hasselback equation. The mono‐ and di‐protonated species' equilibrium constants (logK1 and logK2) were calculated as ~5.0. This value may be promising for pH‐sensitizing photosensitizers. Also, the photophysical and photochemical properties of synthesized metallophthalocyanine derivatives (2) and (5) were studied at different pH values. The singlet oxygen quantum yield of (2) and (5) was calculated to be 0.78 and 0.81 in DMSO, respectively. When pH = 6.4, that is, tumor‐pH‐values, this value for (5) has increased to 0.92. The newly synthesized phthalocyanines are suitable photosensitizers for PDT applications, especially with high singlet oxygen quantum yield at pH 6.4.

Consequences of elevated CO2 on soil acidification, cation depletion, and inorganic carbon: A column-based experimental investigation

The anthropogenic release of atmospheric CO2 affects soil nutrient cycling through varied biogeochemical processes. Cation depletion from exchange sites, carbonate mineral dissolution, and subsequent changes in organic and inorganic carbon flux are growing concerns for soil health and sustainability. Particularly, the effects of acid deposition on soil pH and soil health under changing global carbon flux is poorly understood. To estimate the magnitude and effects of pH change across different soil profiles, the depth-wise response of soil cations, pH, and soil inorganic carbon (SIC) to varying CO2 levels was investigated using column-leachate experiments. Six soils, representing acidic, neutral, and alkaline pH, were exposed to different CO2 enrichments (100%, 10%, 1%, and Control) of water percolate for 30 days. Analysis of the column leachates revealed that the base cations (Ca, Mg, Na) were higher initially than on day 30, while Si leaching increased with time. The pH in leachates tended to attain an equilibrium state with time under CO2 saturation, indicating the buffering capacity of alkaline and neutral soils. Evaluation of the soil before and after the experiments showed that the solid SIC, such as carbonate minerals and any dissolved SIC components (e.g., carbonate, bicarbonate ions) entrained in the pore space increased, whereas the potential cation exchange capacity (PCEC) decreased in all soils. This trend was especially prominent for alkaline soils at 100% CO2 enrichment. Over the short-term study, the SIC showed minimal response to varying CO2 enrichment conditions in neutral and acidic soils. The altered cation concentrations in the leachates suggest that under long-term exposure to elevated CO2, a deficiency of cationic essential plant nutrients such as Ca2+, Mg2+, and K+ is likely, especially with low buffering capacity and primary mineral content. In contrast, an increase in nutrient solubility and elemental toxicity (e.g., Al3+ Mn) can be observed in the short term. The initial soils with greater ECEC experienced an increased SIC leaching in the shorter term and suggested potential deposition in deeper layers. The resultant SIC loss might be amplified in arid to semi-arid soils with low SIC and affect soil health.

Highly sensitive amperometric food sensor for Sudan-I dye using nanocomposites modified working electrode

Sudan-I dye (1-phenyl azo-2-naphthol) is commonly used as a coloring agent in the food and textile industries. The excessive use of Sudan-I dye has ill effects on human health. A sensitive and selective electrochemical detection is required for sensing Sudan-I dye in food products. An electrochemical sensor based on a modified working electrode using ternary mixed metal oxide (Ti/Fe/CuO) nanocomposites was developed for sensing Sudan-I dye. Using a modified Sol-gel technique, Ti/Fe/CuO mixed metal nanocomposites were synthesized. FT-IR, UV–Visible, SEM, and XRD techniques were used to characterize the Ti/Fe/CuO nanocomposites. Different voltammetric techniques, such as Cyclic voltammetry (CV), Differential Pulse Voltammetry (DPV), and Linear Sweep Voltammetric (LSV) were used for qualitative and quantitative estimation of Sudan-I dye. Electrochemical Impedance Spectroscopy (EIS) was used for structural information of interface. The specially designed working electrode acted as a sensor and shows good sensing ability toward Sudan-I dye in real food samples. A linear range of 0–160 µM and 0–200 µM for red chili sauce and powder (real samples), respectively was observed. Under the optimized condition, the current response was linear with a detection limit of 0.02 µM/L. A characteristic oxidation peak of 7263.36 µA at 0.2606 V and a reductive peak of − 1465 μA at − 0.3714 V are the characteristic peaks for Sudan-I dye. The effect of change in pH, scan rate, storage, stability behavior, and concentration of Sudan-I dye was evaluated. A comparative study was done between glassy carbon electrodes, bare Copper metal, and ternary metal oxide NCs modified electrodes. The developed electrochemical sensor demonstrated reliability, reproducibility, stability, speed, and non-specificity, making it suitable for both quantitative and qualitative analysis of food additives, preservatives, coloring agents, and flavoring agents.

Investigating the combined effects of pH changes and UV radiation exposure on dissolved metal-humate complexes: an important process in aquatic systems.

An in vitro study was carried out to examine the impact of UV exposure on metal-dissolved humic material (M-DHM) complexes in aqueous systems at different pH. Complexation reactions of dissolved M (Cu, Ni, and Cd) with DHM increased with the increasing pH of the solution. Kinetically inert M-DHM complexes dominated at higher pH in the test solutions. Exposure to UV radiation did affect the chemical speciation of M-DHM complexes at different pH of the systems. The overall observation suggests that exposure to increasing UV radiation increased the lability, mobility, and bioavailability of M-DHM complexes in aquatic environments. The dissociation rate constant of Cu-DHM was found to be slower than Ni-DHM and Cd-DHM complexes (both before and after UV exposure). At a higher pH range, Cd-DHM complexes dissociated after exposure to UV radiation and a part of this dissociated Cd precipitated out from the system. No change in the lability of the produced Cu-DHM and Ni-DHM complexes after UV radiation exposure was observed. They did not appear to form new kinetically inert complexes even after 12 h of exposure. The outcome of this research has important global implications. The results of this study helped to understand DHM leachability from soil and its effect on dissolved metal concentrations in the Northern Hemisphere water bodies. The results of this study also facilitated to comprehend the fate of M-DHM complexes at photic depths (where pH changes are accompanied by high UV radiation exposure) in tropical marine/freshwater systems during summer.

Analysis of the effect of using divalent and trivalent iron compounds on sludge dewatering performance in thickening units

Abstract Sludge is one of the by-products of wastewater treatment plants (WWTPs). To assist biological processes, part of the produced sludge is returned to the treatment process and the excess is removed from the treatment plant whereby it undergoes thickening and dewatering. Numerous studies have been conducted to investigate the effect of different coagulants on dewatering from sludge, but the effect of using divalent iron for this purpose has not been investigated so far. In this research, the effect of divalent and trivalent iron compounds (ferrous sulfate and ferric chloride) on the dewatering of excess sludge of the first module of the Bojnourd WWTP (Iran) has been investigated. In this regard, first, the effect of different doses of each coagulant to optimize the dewatering characteristics of sludge was investigated and then the effect of pH change by adding lime was investigated. The results showed that the addition of optimal doses of FeSO4 (0.6 and 0.4 g/l) and lime (0.664 and 1.5866 g/l) reduced the capillary suction time of sludge by 30.6 and 32.7%, respectively, while reducing the moisture content of sludge cake by 26 and 30.6%.

The Effect of Saliva Ph on the Electrical Galvanic Current Between Titanium Implant and Cobalt Chromium Bar Attachment

Objectives: The present study was carried out to evaluate the effect of Ph changes of the saliva on the electrical galvanic currents between the anodizing titanium implant with cobalt chromium bar attachment. Material and methods: Eighteen dental implants (9 model each model 2 dental implants with bar). Every two titanium implants were inserted within acrylic block, a cobalt chromium bar was used to connect the two implants and attached to it with titanium screws. The blocks of acrylic resin with dental implant and cobalt chromium bar classified into three groups according to the artificial saliva Ph (neutral, acidic and alkaline). Following immersion in artificial saliva the flow of galvanic current between titanium dental implant and cobalt chromium bar was measured after 7 and 30 days. The data was statistically analysis used F-test (ANOVA) to compare between the groups and post hoc test (LSD) for pairwise comparison. Results: the result of this study showed that there was statistically significant different between the groups, with higher galvanic current in acidic Ph group. Conclusion: Within the limitation of this in vitro study, there where galvanic current between titanium dental implant when coupled with cobalt chrome bar and it significantly increased with the time especially when immersed in acidic media.

Light-driven Proton Pumps as a Potential Regulator for Carbon Fixation in Marine Diatoms.

Diatoms are a major phytoplankton group responsible for approximately 20% of carbon fixation on Earth. They perform photosynthesis using light-harvesting chlo-rophylls located in plastids, an organelle obtained through eukaryote-eukaryote endosymbiosis. Microbial rhodopsin, a photoreceptor distinct from chlo-rophyll-based photosystems, was recently identified in some diatoms. However, the physiological function of diatom rhodopsin remains unclear. Heterologous expression techniques were herein used to investigate the protein function and subcellular localization of diatom rhodopsin. We demonstrated that diatom rhodopsin acts as a light-driven proton pump and localizes primarily to the outermost membrane of four membrane-bound complex plastids. Using model simulations, we also examined the effects of pH changes inside the plastid due to rhodopsin-mediated proton transport on photosynthesis. The results obtained suggested the involvement of rhodopsin-mediated local pH changes in a photosynthetic CO2-concentrating mechanism in rhodopsin-possessing diatoms.

Adsorption of Lead (ii), Chromium (vi) and Manganese (ii) metal ions from water using modified Pennisetum purpureum Schumach plant stalk

Water pollution is a global problem affecting humanity. Availability of clean water is a fundamental prerequisite to public health safety and the survival of the human race as well as animals. However, pollution of river water by heavy metal ions deposition is a grave environmental problem. Presence of the heavy metals in the water, pose a serious health risk particularly to rural populations which rely majorly on the river water for domestic purposes. Several methods for elimination of the heavy metal pollutants from river waters have been previously employed. However, most of these methods are expensive and cumbersome, hence not sustainable. This research explored the potential of modified Pennisetum purpureum Schumach plant adsorbent in removal of Lead (II), Manganese (II) and Chromium (VI) ions from spiked water samples by adsorption. Surface analysis of the adsorbent using FTIR Photometer confirmed presence of functional groups such as -NH2, C=O and O-H responsible for adsorption of heavy metal ions. Concentration of heavy metal ions in water samples was determined before and after adsorption process using Atomic Absorption Spectroscopy (AAS) and means concentration computed. Effect of changes in pH on adsorption was investigated by conducting adsorption at three different pH conditions of 5, 7 and 9. Modification of the adsorbent surface improved its adsorption capacity. For instance, at pH 5, adsorption of Cr+6 increased from 12% to 14.82% when modified adsorbent was used. The modified adsorbent achieved greater % adsorption in all the three metals. Increase in the pH of adsorption from 5 to 9 had a reducing effect on the percent adsorption. At pH of 5 the % adsorption of Pb+2 reduced from 90.26% to 73.75% at pH of 9. This reductions in percentage adsorption were recorded for Pb+2 and Mn+2 ions but not significant for Cr+6 ions. These results show the potential of P. purpureum plant for use as an adsorbent in purification/detoxification of river water which would present a cheaper and more readily available alternative to many current adsorbents and adsorption methods in use. However further research is needed to determine the optimal set of conditions as well as the most suitable modification treatment for maximum adsorption.

Effect of pH Change on the Microalgae-Based Biogas Upgrading Process

An alternative way to remove CO2 from biogas is the use of photosynthetic microorganisms, such as microalgae. This can be achieved by the operation of an open photobioreactor, connected with a mass transfer column, such as a counterflow column. This technology provides up-graded biogas with high quality. The microalgal uptake of CO2 from the biogas in counterflow columns generates pH changes in microalgae culture. To clarify the potential effect of these dynamic pH conditions in the culture, the effect of pH change on the photosynthetic activity and PSII quantum yield was studied for microalgae Chlorella sorokiniana. Thus, assays were carried out, where the pH drop reported in the counterflow columns was replicated in batch microalgae culture through HCl addition and CO2 injection, moving the culture pH from 7.0 to 5.0 and from 7.0 to 5.8, respectively. Moreover, the effect of light/darkness on photosynthetic activity was tested when the pH decreased. The results obtained in this research showed that the photosynthetic activity decreased for the light conditions when the pH was shifted by HCl addition and CO2 injection. Despite this, the value of the PSII quantum yield remained at 0.6–0.7, which means that the microalgae culture did not suffer a negative effect on the photosynthetic system of cells because a high value of PSII efficiency remained. In the same way, the results indicated that when the pH change was corrected, the photosynthetic activity recovered. Moreover, the apparent affinity constant for dissolved inorganic carbon (KDIC) was 0.9 µM at pH 5 and 112.0 µM at pH 7, which suggests that the preferred carbon source for C.sorokniana is CO2. Finally, all the results obtained indicated that the pH drop in the counter-flow column for biogas upgrading did not cause permanent damage to the photosynthetic system, and the decrease in the photosynthetic activity as a result of the pH drop can be recovered when the pH is corrected.

Long-term differences in fertilisation type change the bacteria:archaea:fungi ratios and reveal a heterogeneous response of the soil microbial ionome in a Haplic Luvisol

Organic farm management through farmyard manure application is associated with soil organic carbon sequestration facilitated by more balanced nutrient stoichiometry of macro- and micronutrients. Quantitative information on micronutrients within the soil microbial biomass is lacking. Using soils from a 40-year old long-term field trial (DOK), we investigated if fertilisation differences (farmyard manure equivalent to 0.7 or 1.4 livestock units per hectare and mineral fertilisation) and farm management (biodynamic, organic, conventional) changed the soil microbial ionome and stoichiometry and if this is related to microbial community shifts. Soil (15% sand, 70% silt and 15% clay) from the top 20 cm was analysed for microbial biomass carbon, nitrogen and phosphorus. Further elements were assessed via an adapted chloroform-fumigation extraction procedure. Abundances of bacteria, archaea, and fungi were determined (qPCR). Farmyard manure increased microbial biomass by approximately two-fold and the contribution of bacteria and archaea by up to approximately five-fold. Microbial biomass phosphorus and magnesium increased with mineral fertilisation (from 7 to 14 μg g−1 soil) and farmyard manure (from 0.5 to 2.7 μg g−1 soil), respectively. The microbial biomass carbon to potassium ratio remained similar, at around 47:1, revealing stoichiometric control. Microbial biomass manganese was reduced from 3.5 to 2.2 μg g−1 soil with lower availability due to raised pH in biodynamic management. The microbial stoichiometry and ionome were mainly affected by nutrient input and soil chemical properties; direct links between microbial (micronutrient-) stoichiometry and microbial community changes cannot be established with certainty due to potential confounding effects of pH changes.