Challenging management dogma where evidence is non-existent, weak, or outdated: part II.

Many dogmas influence daily clinical practice, and critical care medicine is no exception. We previously highlighted the weak, questionable, and often contrary evidence base underpinning four established medical managements-loop diuretics for acute heart failure, routine use of heparin thromboprophylaxis, rate of sodium correction for hyponatremia, and 'every hour counts' for treating bacterial meningitis. We now provide four further examples in this "Dogma II" piece (a week's course of antibiotics, diabetic ketoacidosis algorithms, sodium bicarbonate to improve ventricular contractility during severe metabolic acidosis, and phosphate replacement for hypophosphatemia) where routine practice warrants re-appraisal.

Current knowledge about pyruvate supplementation: A brief review.

Pyruvate is a three-carbon ketoacid that occurs naturally in cells. It is produced through enzymatic reactions in the glycolytic pathway and plays a crucial role in energy metabolism. Despite promising early results, later well-controlled studies of physically active people have shown that pyruvate supplementation lasting more than 1 week has no ergogenic effects. However, some data suggest that ingested pyruvate may be preferentially metabolized without accumulation in the bloodstream. Pyruvate exhibits antioxidant activity and can affect the cellular redox state, and exogenous pyruvate can influence metabolism by affecting the acid-base balance of the blood. This brief review focuses on the potential effects of pyruvate as a supplement for active people. The current state of understanding suggests that studies of the effects of pyruvate supplementation should prioritize investigating the timing of pyruvate intake.

The challenged urine bicarbonate excretion test in cystic fibrosis: A comprehensive analysis of urine acid/base parameters.

AIM: Renal excretion of excess HCO3 - depends on renal cystic fibrosis transmembrane conductance regulator (CFTR) and is impaired in people with cystic fibrosis (pwCF). Urine HCO3 - excretion following oral NaHCO3-loading may be a simple in vivo biomarker of CFTR function. In this study, we investigated changes in urine acid/base parameters following oral NaHCO3-loading to comprehensively assess the physiological response to the test and evaluate HCO3 - as the primary test result. METHODS: Urine acid/base parameters (titratable acid (TA), NH4 +, net acid excretion (NAE) and pH) were measured in bio-banked urine samples from controls (n = 10) and pwCF (n = 50) who completed the challenged urine HCO3 - test. The association between urine acid/base excretion parameters and clinical CF disease characteristics and CFTR modulator therapy-induced changes were assessed. RESULTS: Before treatment, challenged urine acid/base excretion associated with important CF disease characteristics. TA excretion and NAE were lower in pwCF with residual function mutations, 7.9 and 16.6 mmol/3 h, respectively, and lower TA excretion and NAE associated with pancreatic sufficiency. A lower excretion of TA, NH4 +, and NAE associated with a higher percentage of predicted FEV1 (1.3%, 2.5% and 0.8% per mmol/3 h higher, respectively). Modulator treatment decreased TA excretion and NAE (-2.9 and -5.3 mmol/3 h, respectively). CONCLUSION: Following acute NaHCO3-loading, increased base excretion is mirrored by decreased acid excretion. Urine HCO3 - excretion sufficiently represents the additional urine acid/base parameters as test result. The observed changes in acid excretion support CFTR modulator-induced increase of CFTR-dependent type B intercalated cell HCO3 - secretion and the use of the challenged urine HCO3 - test as a possible CFTR-biomarker.

An assessment on the effects of buffers on the productive, behavioral and metabolic parameters of Holstein dairy cows.

This study aimed to evaluate the impact of supplementing sodium bicarbonate or a commercial blend of buffering agents (BBA) comprising calcareous calcitic, magnesium oxide, calcareous algae, and sodium bicarbonate on the productive, behavioral and metabolic parameters of Holstein cows fed starchy diets. Over a 60-day trial period, thirty-six multiparous cows with an average milk yield of 38.84 ± 9.24 kg/day and 63.74 ± 18.63 days in milk (DIM), were randomly divided into two groups. The control group (n = 18) received a supplementation of 1.1% dry matter (DM) of sodium bicarbonate (Raudi®, Totalmix, Brazil), while the BBA group (n = 18) was administered with 0.5% DM of a blend of buffering agents (Equalizer®, Nutron/Cargill, Brazil). The mean values of ruminal pH (control 6.80 ± 0.06 and BBA 6.77 ± 0.06; P > 0.05) and volatile fatty acid (VFA) production (control: acetate 62.63 ± 1.29%, propionate 22.99 ± 1.07%, butyrate 14.30 ± 0.52%; BBA: acetate 63.07 ± 1.32%, propionate 23.47 ± 1.10%, butyrate 13.70 ± 0.57%), were similar (P > 0,05) between the two groups. The value of faecal pH was higher (P < 0.05) in the BBA group (6.25 ± 0.02) than the control group (6.12 ± 0.02). Animals treated with BBA exhibited lower (P < 0,05) dry matter intake (DMI) (24.75 ± 0.64 kg/day), higher feed efficiency (FE) (1.64 ± 0.03), and reduced feeding frequency (52.89 ± 3.73 n°/day) than the control group (DMI, 26.75 ± 0.62 kg/day; FE, 1.50 ± 0.03; feeding frequency, 66.07 ± 3.64 n°/day). Milk production remained similar across both groups (control, 39.11 ± 0.92 kg/day and BBA, 39.87 ± 0.92 kg/day; P > 0.05). Notably, the control group displayed a higher (P < 0,05) concentration of milk protein (1.21 ± 0.05 kg/day) than the BBA (1.18 ± 0.05 kg/day) group. The study concluded that both treatments effectively buffered the rumen and mitigated the risk of ruminal acidosis. Moreover, the higher faecal pH in the BBA-treated group suggests potential intestinal action attributable to the synergistic effects of diverse additives with buffering properties. Despite a reduced DMI, BBA-treated animals exhibited improved FE.

Efficacy of anti-hyperkalemic agents during cardiopulmonary resuscitation in out-of-hospital cardiac arrest.

Aim: We assessed the efficacy of anti-hyperkalemic agents for alleviating hyperkalemia and improving clinical outcomes in patients with out-of-hospital cardiac arrest (OHCA). Methods: This was a single-center, retrospective observational study of OHCA patients treated at tertiary hospitals between 2010 and 2020. Adult patients aged 18 or older who were in cardiac arrest at the time of arrival and had records of potassium levels measured during cardiac arrest were included. A linear regression model was used to evaluate the relationship between changes in potassium levels and use of anti-hyperkalemic medications. Cox proportional hazards regression analysis was performed to analyze the relationship between the use of anti-hyperkalemic agents and the achievement of return of spontaneous circulation (ROSC). Results: Among 839 episodes, 465 patients received anti-hyperkalemic medication before ROSC. The rate of ROSC was higher in the no anti-hyperkalemic group than in the anti-hyperkalemic group (55.9 % vs 47.7 %, P = 0.019). The decrease in potassium level in the anti-hyperkalemic group from pre-ROSC to post-ROSC was significantly greater than that in the no anti-hyperkalemic group (coefficient 0.38, 95 % confidence interval [CI], 0.13-0.64, P = 0.003). In Cox proportional hazards regression analysis, the use of anti-hyperkalemic medication was related to a decreased ROSC rate in the overall group (adjusted hazard ratio [aHR] 0.66, 95 % CI, 0.54-0.81, P < 0.001), but there were no differences among subgroups classified according to initial potassium levels. Conclusions: Anti-hyperkalemic agents were associated with substantial decreases in potassium levels in OHCA patients. However, administration of anti-hyperkalemic agents did not affect the achievement of ROSC.

Efficacy and safety of oral sodium bicarbonate in kidney-transplant recipients and non-transplant patients with chronic kidney disease: a systematic review and meta-analysis.

Introduction: We investigated the efficacy and safety of oral sodium bicarbonate in kidney-transplant recipients and non-transplant patients with chronic kidney disease (CKD), which are currently unclear. Methods: PubMed, Cochrane Library, Embase, and Web of Science were searched for randomized controlled trials investigating the efficacy and safety of sodium bicarbonate versus placebo or standard treatment in kidney-transplant and non-transplant patients with CKD. Results: Sixteen studies of kidney-transplant recipients (two studies, 280 patients) and non-transplant patients with CKD (14 studies, 1,380 patients) were included. With non-transplant patients, sodium bicarbonate slowed kidney-function declines (standardized mean difference [SMD]: 0.49, 95% confidence interval [CI]: 0.14-0.85, p = 0.006) within ≥12 months (SMD: 0.75 [95% CI: 0.12-1.38], p = 0.02), baseline-serum bicarbonate <22 mmol/L (SMD: 0.41 [95% CI: 0.19-0.64], p = 0.0004) and increased serum-bicarbonate levels (mean difference [MD]: 2.35 [95% CI: 1.40-3.30], p < 0.00001). In kidney-transplant recipients, sodium bicarbonate did not preserve graft function (SMD: -0.07 [95% CI: -0.30-0.16], p = 0.56) but increased blood pH levels (MD: 0.02 [95% CI: 0.00-0.04], p = 0.02). No significant adverse events occurred in the kidney-transplant or non-transplant patients (risk ratio [RR]: 0.89, [95% CI: 0.47-1.67], p = 0.72; and RR 1.30 [95% CI: 0.84-2.00], p = 0.24, respectively). However, oral sodium bicarbonate correlated with increased diastolic pressure and worsened hypertension and edema (MD: 2.21 [95% CI: 0.67-3.75], p = 0.005; RR: 1.44 [95% CI: 1.11-1.88], p = 0.007; and RR: 1.28 [95% CI: 1.00-1.63], p = 0.05, respectively). Discussion: Oral sodium bicarbonate may slow kidney-function decline in non-transplant patients with CKD taking sodium bicarbonate supplementation for ≥12 months or a baseline serum bicarbonate level of <22 mmol/L, without preserving graft function in kidney-transplant recipients. Sodium bicarbonate may increase diastolic pressure, and elevate a higher incidence of worsening hypertension and edema. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42023413929.

Comparison of lidocaine bicarbonate with fentanyl and chloroprocaine for epidural anesthesia during cesarean section: a randomized, controlled, double-blind clinical trial.

Chloroprocaine and lidocaine bicarbonate are commonly used for epidural anesthesia because of their rapid onset, particularly in the case of conversion from epidural labor analgesia to emergency cesarean section. However, it is unclear whether lidocaine bicarbonate combined with fentanyl has an advantage over chloroprocaine alone in emergency cesarean section. In this study, 102 women who underwent elective cesarean section received 15 mL 3% chloroprocaine and 1 mL saline (CP group) or 15 mL 1.73% lidocaine bicarbonate and 1 mL fentanyl 50 µg (LF group) for epidural anesthesia. Nociceptive block level was assessed by pinprick and recorded every minute. The primary outcome was the onset time to T6 block. The median onset time to T6 analgesia was 10 [10, 10] min in the CP group and 10 [7, 10] min in the LF group (COX model for CP versus LF, HR 0.47, 95% CI 0.23-0.95, p = 0.035). The median onset time to T8 analgesia was 7 [5, 9] min in CP group and 5 [4, 7] min in LF group (COX model for CP versus LF, HR 0.61, 95% CI 0.39-0.95, p = 0.027). The proportion of hypotension episodes occurring before delivery in LF group was lower than that in CP group (p = 0.011). The incidence of block level ≥ T4 after supplemental dosing in the LF group was lower than that in the CP group (p = 0.031). Compared with 3% chloroprocaine, 1.73% lidocaine bicarbonate combined with fentanyl 50 µg has a slightly faster onset time and less hypotension in epidural anesthesia for cesarean section. Clinical Trial Registration: http://www.chictr.org.cn/index.html, identifier ChiCTR2200056180.

Effect of ultrasound-assisted treatment on meat tenderization for elderly individuals.

This study evaluated the effect of ultrasound using papain and sodium bicarbonate (SC) on meat tenderness to achieve the desired texture for elderly individuals. Meats were immersed in distilled water (DW) or papain (PI), ultrasonically treated with papain (UPI), or ultrasonically treated with papain and SC (UPIS). Response surface methodology was used to optimize the processing conditions with the lowest hardness, and the optimal conditions were determined as follows: 400 U/mL papain, ultrasonic for 30 min, and 4% SC. Hardness, color, and myofibrillar fragmentation index (MFI) were investigated. The hardness followed the order of DW (22.50 N), PI (18.62 N), UPI (12.08 N), and UPIS (7.16 N), and UPIS showed the highest MFI. Papain and SC affected the color of the meat. Overall, ultrasound-assisted treatment using papain and SC resulted in hardness levels of less than 7.8 N, which can be easily compressed by low tongue pressure.

Bacterial ß-carbonic anhydrases.

ß-Carbonic anhydrases (ß-CA; EC 4.2.1.1) are widespread zinc metalloenzymes which catalyze the interconversion of carbon dioxide and bicarbonate. They have been isolated in many pathogenic and non-pathogenic bacteria where they are involved in multiple roles, often related to their growth and survival. ß-CAs are structurally distant from the CAs of other classes. In the active site, located at the interface of a fundamental dimer, the zinc ion is coordinated to two cysteines and one histidine. ß-CAs have been divided in two subgroups depending on the nature of the fourth ligand on the zinc ion: class I have a zinc open configuration with a hydroxide ion completing the metal coordination, which is the catalytically active species in the mechanism proposed for the ß-CAs similar to the well-known of α-CAs, while in class II an Asp residue substitute the hydroxide. This latter active site configuration has been showed to be typical of an inactive form at pH below 8. An Asp-Arg dyad is thought to play a key role in the pH-induced catalytic switch regulating the opening and closing of the active site in class II ß-CAs, by displacing the zinc-bound solvent molecule. An allosteric site well-suited for bicarbonate stabilizes the inactive form. This bicarbonate binding site is composed by a triad of well conserved residues, strictly connected to the coordination state of the zinc ion. Moreover, the escort site is a promiscuous site for a variety of ligands, including bicarbonate, at the dimer interface, which may be the route for bicarbonate to the allosteric site.

Lauric acid improved the quality of fresh noodles with/without sodium bicarbonate by altering physical properties and structure of wheat starch.

To know the influence of lauric acid (LA) on wheat flour fresh noodles (WFN) quality and the latent mechanism, the effect of LA on cooking properties, digestibility and structure of WFN with/without sodium bicarbonate (SB) and the properties of wheat flour (WF) with/without SB were studied. The results indicated that LA reduced cooking loss and digestibility of WFN with SB and slightly decreased water adsorption and increased the free water binding ability and hardness of WFN without SB. Furthermore, LA increased the degree of short- and long-range order and molecular weight of starch in cooked WFN with/without SB and it had greater effect on the degree of short- and long-range order and molecular weight of starch in cooked WFN with SB than that without SB. Differential scanning calorimeter (DSC) and rapid viscosity analysis (RVA) displayed that WFN with LA and SB formed more starch-LA or/and starch-LA-protein complexes than WFN with LA. Additionally, the impact of LA on WFN quality and WF properties was influenced by SB concentration. This study will provide theoretical basis and new thoughts for the design of high-quality fresh noodles with low digestibility, low cooking loss and high hardness.

Staphylococcus aureus Stress Response to Bicarbonate Depletion.

Bicarbonate and CO2 are essential substrates for carboxylation reactions in bacterial central metabolism. In Staphylococcus aureus, the bicarbonate transporter, MpsABC (membrane potential-generating system) is the only carbon concentrating system. An mpsABC deletion mutant can hardly grow in ambient air. In this study, we investigated the changes that occur in S. aureus when it suffers from CO2/bicarbonate deficiency. Electron microscopy revealed that ΔmpsABC has a twofold thicker cell wall thickness compared to the parent strain. The mutant was also substantially inert to cell lysis induced by lysostaphin and the non-ionic surfactant Triton X-100. Mass spectrometry analysis of muropeptides revealed the incorporation of alanine into the pentaglycine interpeptide bridge, which explains the mutant's lysostaphin resistance. Flow cytometry analysis of wall teichoic acid (WTA) glycosylation patterns revealed a significantly lower α-glycosylated and higher ß-glycosylated WTA, explaining the mutant's increased resistance towards Triton X-100. Comparative transcriptome analysis showed altered gene expression profiles. Autolysin-encoding genes such as sceD, a lytic transglycosylase encoding gene, were upregulated, like in vancomycin-intermediate S. aureus mutants (VISA). Genes related to cell wall-anchored proteins, secreted proteins, transporters, and toxins were downregulated. Overall, we demonstrate that bicarbonate deficiency is a stress response that causes changes in cell wall composition and global gene expression resulting in increased resilience to cell wall lytic enzymes and detergents.

Inorganic carbon utilization strategies of plateau aquatic plants in response to native habitats.

Aquatic plants are a crucial component of the aquatic ecosystem in the Tibetan Plateau region. Researching the adaptability of plateau aquatic plants in photosynthesis to the plateau environment can enhance understanding of the operational mechanisms of plateau ecosystems, thereby providing a scientific basis for the protection and management of plateau aquatic ecosystems. This study presents an investigation of photosynthetic inorganic carbon utilization strategies and photosynthetic efficiency of 17 aquatic plants under natural growing conditions in Niyang River basin on the Tibetan Plateau. In pH-drift experiments, 10 of 17 species were able to utilize HCO3-, and environmental factors like water pH were shown to have a significant effect on the ability of the tested species to utilize HCO3-. Titratable acidity in the leaves of Stuckenia filiformis, Zannichellia palustris, Batrachium bungei, and Myriophyllum spicatum showed significant diurnal fluctuations at certain sampling sites, indicating the presence of CAM. In B. bungei, water pH positively correlated with CAM activity, while CO2 concentration negatively correlated with CAM activity. The chlorophyll fluorescence analysis revealed that aquatic plants inhabiting the Tibetan Plateau exhibited photosynthetic adaptations. In conclusion, the aquatic plants on the Tibetan Plateau employ diverse strategies for utilizing inorganic carbon during photosynthesis, exhibiting their flexible adaptability to the native high-altitude habitats of the Tibetan Plateau.

A global survey of bicarbonate stress-induced pre-mRNA alternative splicing in soybean via integrative analysis of Iso-seq and RNA-seq.

Alternative splicing (AS) plays important roles in modulating environmental stress responses in plants. However, little is known about the functions of bicarbonate-induced AS in cultivated soybean (Glycine max L. Merr.). In this study, we combined PacBio isoform sequencing (Iso-seq) and Illumina RNA sequencing (RNA-seq) to elucidate the bicarbonate-induced AS events in soybean root and leaf tissues. Compared to RNA-seq, Iso-seq identified more novel genes and transcripts, as well as more AS events, indicating that Iso-seq is more efficient in AS detection. Combining these two technologies, we found that intron retention (IR) is the most frequent AS event type. We identified a total of 913 and 1974 bicarbonate stress-responsive differentially alternative spliced genes (DAGs) in soybean leaves and roots respectively, from our RNA-seq results. Additionally, we determined a transcription factor (GmNTL9) and a splicing factor (GmRSZ22), and validated their roles in bicarbonate stress response by AS. Overall, our study opens an avenue for evaluating plant AS regulatory networks, and the obtained global landscape of alternative splicing provides valuable insights into the AS-mediated bicarbonate-responsive mechanisms in plant species.

A Synopsis on CO2 Capture by Synthetic Hydrogen Bonding Receptors.

Carbon dioxide (CO2) is one of the most abundant greenhouse gases in Earth's atmosphere and responsible for global warming. Therefore, aerial CO2 capture and sequestration has become a major task for human community. Though several adsorbents for CO2 including activated carbon, zeolites, metal-organic frameworks (MOFs), and other surface-modified porous materials are well developed, the supramolecular approaches using synthetic hydrogen-bonding receptors are less explored. This review article highlights the synthetic development of various artificial receptors and their properties toward fixation of aerial CO2 as carbonate (CO32-), bicarbonate (HCO3-), or carbamate (-NHCOO-/>NCOO-) ions, induced by excess fluoride (F-) or hydroxide (OH-) ions as their tetrabutylammonium salts. The utilization of encapsulated carbonate/bicarbonate/carbamate complexes in anion exchange metathesis for separation of oxyanions from aqueous solutions are also discussed. In addition, the release of CO2 and regeneration of receptor molecules are described in a number of occasions. Most importantly, the formation of anion complexes as crystalline materials in solid-state is described in terms of supramolecular chemistry and correlated with their solution-state properties. Finally, the types of receptors containing various functional groups are scrutinized in CO2 uptake, storage, and release processes and hints of endeavours for future research are delineated.

Kidney and Cardiovascular Protection Using Dietary Acid Reduction in Primary Hypertension: A Five-Year, Interventional, Randomized, Control Trial.

BACKGROUND: High fruit and vegetable diets are associated with reduced chronic kidney disease and cardiovascular disease but are infrequently used in hypertension treatment. Low acid diets are also associated with reduced chronic kidney disease and cardiovascular disease, and fruits and vegetables or oral sodium bicarbonate (NaHCO3) lowers dietary acid. METHODS: We randomized 153 hypertensive macroalbuminuric patients receiving pharmacologic chronic kidney disease and cardiovascular disease protection to get fruits and vegetables, oral NaHCO3, or Usual Care. We assessed the course of kidney disease progression and cardiovascular disease risk indices over five years. RESULTS: Chronic kidney disease progression was slower in participants receiving fruits and vegetables or oral NaHCO3 than Usual Care [mean (SE)] [-1.08 (0.06) and -1.17 (0.07) vs. -1.94 (0.11) mL/min/1.73m2/ year, respectively, P's< .001). Yet, systolic blood pressure was lower, and cardiovascular disease risk indices improved more in participants receiving fruits and vegetables than in those receiving NaHCO3 or Usual Care. These cardiovascular benefits of fruits and vegetables were achieved despite lower doses of pharmacologic chronic kidney disease and cardiovascular disease protection. CONCLUSION: The trial supports fruits and vegetables as foundational hypertension treatment to reduce chronic kidney disease progression and cardiovascular disease risk.

Evaluating hydrogen ion mobilization during hemodialysis using only predialysis and postdialysis blood bicarbonate concentrations.

INTRODUCTION: The hydrogen ion (H+) mobilization model has been previously shown to provide a quantitative description of intradialytic changes in blood bicarbonate (HCO3) concentration during hemodialysis (HD). The current study evaluated the accuracy of different methods for estimating the H+ mobilization parameter (Hm) from this model. METHODS: The study compared estimates of the H+ mobilization parameter using predialysis, hourly during the HD treatment, and postdialysis blood HCO3 concentrations (Hm-full2) with those determined using only predialysis and postdialysis blood HCO3 concentrations assuming steady state conditions (Hm-SS2) during the midweek treatment in 24 chronic HD patients treated thrice weekly. RESULTS: Estimated Hm-full2 values (0.163 ± 0.079 L/min [mean ± standard deviation]) were higher than, but not statistically different (p = 0.067) from, those of Hm-SS2 (0.152 ± 0.065 L/min); the values of Hm-full2 and Hm-SS2 were highly correlated with a correlation coefficient of 0.948 and a mean difference that was small (0.011 L/min). Further, the H+ mobilization parameter values calculated using only predialysis and postdialysis blood HCO3 concentrations during the first and third HD treatments of the week were not different from those calculated during the midweek treatment. CONCLUSIONS: The H+ mobilization model can be used to provide estimates of the H+ mobilization parameter without the need to measure hourly intradialytic blood HCO3 concentrations.

Arsenic release during groundwater recharge and effects of coexisting ions in a typical inland basin with high arsenic concentration: Modeling and batch experiment.

Groundwater recharge is a viable solution to groundwater overexploitation. However, the injection of recharge water may break the dissolution balance and induce the release of trace elements especially arsenic (As), which has been identified in river deltas. Only a few studies have been conducted in inland basins with high As concentration, high pH, and low Eh. Aiming to analyze As release with groundwater recharge in inland high-As regions and determine the effects of coexisting ions in recharge water, this study established PHase Equilibria Calculation (PHREEQC) models using rainwater and groundwater data from three inland sedimentary basins with slow groundwater flow in semi-arid regions. The simulations fitted with the batch experiments, achieving an R-squared (R2) of 0.98. The coexisting ions in the recharge water significantly affected As release during recharge. Ca2+ inhibited the release of total arsenic (Total-As) by increasing the surface charge of iron oxides. NO3- inhibited Total-As release by promoting the conversion of trivalent As into pentavalent As. Conversely, HCO3- facilitated As release by competing with arsenate for adsorption sites. On the basis of the modeling and batch experiment results, Total-As release with groundwater recharge was predicted. The results indicated that the high Ca2+ concentration in the recharge water inhibited the As release by 83.5 %, which can be used as a strategy to control As release during groundwater recharge in high-As inland basins.

A potential CO2 carrier to improve the utilization of HCO3- by plant-soil ecosystem for carbon sink enhancement.

INTRODUCTION: Improving the rhizospheric HCO3- utilization of plant-soil ecosystem could increase the carbon sink effect of terrestrial ecosystem. However, to avoid its physiological stress on the crop growth, the dosage of HCO3- allowed to add into the rhizosphere soil was always low (i.e., <5-20 mol/m3). OBJECTIVES: To facilitate the utilization of relatively high concentrations of HCO3- by plants in the pursuit of achieving terrestrial carbon sink enhancement. METHODS: In this study, the feasibility of directly supplementing a high concentration HCO3- carried by the biogas slurry to the plant rhizosphere was investigated using the tomato as a model plant. RESULTS: The CO2-rich biogas slurry was verified as a potential CO2 carrier to increase the rhizospheric HCO3- concentration to 36 mol/m3 without causing a physiological stress. About 88.3 % of HCO3- carried by biogas slurry was successfully fixed by tomato-soil ecosystem, in which 43.8 % of HCO3- was assimilated by tomato roots for the metabolism, 0.5 ‰ of HCO3- was used by microorganisms for substances synthesis of cell structure through dark fixation, and 44.4 % of HCO3- was retained in the soil. The rest of HCO3- (∼11.7 %) might escape into the atmosphere through the reaction with H+. Correspondingly, the carbon fixation of tomato-soil ecosystem increased by 150.1 g-CO2/m2-soil during a tomato growth cycle. As for the global countries that would adopt the strategy proposed in this study to cultivate the tomato, an extra carbon sink of soil with about 1031.1 kt-C per year (i.e., an additional 0.21 tons of carbon per hectare soil) could be obtained. CONCLUSION: This would be consistent with the goal of soil carbon sink enhancement launched at COP21. Furthermore, the regions with low GDP per capita may easily achieve a high reduction potential of CO2 emissions from the agricultural land after adopting the irrigation of CO2-rich biogas slurry.

Ciliary Motility Decreased by a CO2/HCO3--Free Solution in Ciliated Human Nasal Epithelial Cells Having a pH Elevated by Carbonic Anhydrase IV.

An application of CO2/HCO3--free solution (Zero-CO2) did not increase intracellular pH (pHi) in ciliated human nasal epithelial cells (c-hNECs), leading to no increase in frequency (CBF) or amplitude (CBA) of the ciliary beating. This study demonstrated that the pHi of c-hNECs expressing carbonic anhydrase IV (CAIV) is high (7.64), while the pHi of ciliated human bronchial epithelial cells (c-hBECs) expressing no CAIV is low (7.10). An extremely high pHi of c-hNECs caused pHi, CBF and CBA to decrease upon Zero-CO2 application, while a low pHi of c-hBECs caused them to increase. An extremely high pHi was generated by a high rate of HCO3- influx via interactions between CAIV and Na+/HCO3- cotransport (NBC) in c-hNECs. An NBC inhibitor (S0859) decreased pHi, CBF and CBA and increased CBF and CBA in c-hNECs upon Zero-CO2 application. In conclusion, the interactions of CAIV and NBC maximize HCO3- influx to increase pHi in c-hNECs. This novel mechanism causes pHi to decrease, leading to no increase in CBF and CBA in c-hNECs upon Zero-CO2 application, and appears to play a crucial role in maintaining pHi, CBF and CBA in c-hNECs periodically exposed to air (0.04% CO2) with respiration.

Bicarbonate concentration influences carbon utilization rates and biochemical profiles of freshwater and marine microalgae.

Selecting the optimal microalgal strain for carbon capture and biomass production is crucial for ensuring the commercial viability of microalgae-based biorefinery processes. This study aimed to evaluate the impact of varying bicarbonate concentrations on the growth rates, inorganic carbon (IC) utilization, and biochemical composition of three freshwater and two marine microalgal species. Parachlorella kessleri, Vischeria cf. stellata, and Porphyridium purpureum achieved the highest carbon removal efficiency (>85%) and biomass production at 6 g L-1 sodium bicarbonate (NaHCO3), while Phaeodactylum tricornutum showed optimal performance at 1 g L-1 NaHCO3. The growth and carbon removal rate of Scenedesmus quadricauda increased with increasing NaHCO3 concentrations, although its highest carbon removal efficiency (∼70%) was lower than the other species. Varying NaHCO3 levels significantly impacted the biochemical composition of P. kessleri, S. quadricauda, and P. purpureum but did not affect the composition of the remaining species. The fatty acid profiles of the microalgae were dominated by C16 and C18 fatty acids, with P. purpureum and P. tricornutum yielding relatively high polyunsaturated fatty acid content ranging between 14% and 30%. Furthermore, bicarbonate concentration had a species-specific effect on the fatty acid and chlorophyll-a content. This study demonstrates the potential of bicarbonate as an effective IC source for microalgal cultivation, highlighting its ability to select microalgal species for various applications based on their carbon capture efficiency and biochemical composition.