Heat resistance of five spoilage microorganisms in a carbonated broth.

Despite their acidic pH, carbonated beverages can be contaminated by spoilage microorganisms. Thermal treatments, before and/or after carbonation, are usually applied to prevent the growth of these microorganisms. However, the impact of CO2 on the heat resistance of spoilage microorganisms has never been studied. A better understanding of the combined impact of CO2 and pH on the heat resistance of spoilage microorganisms commonly found in carbonated beverages might allow to optimize thermal treatment. Five microorganisms were selected for this study: Alicyclobacillus acidoterrestris (spores), Aspergillus niger (spores), Byssochlamys fulva (spores), Saccharomyces cerevisiae (vegetative cells), and Zygosaccharomyces parabailii (vegetative cells). A method was developed to assess the impact of heat treatments in carbonated media on microbial resistance. The heat resistances of the five studied species are coherent with the literature, when data were available. However, neither the dissolved CO2 concentration (from 0 to 7 g/L), nor the pH (from 2.8 to 4.1) have an impact on the heat resistance of the selected microorganisms, except for As. niger, for which the presence of dissolved CO2 reduced the heat resistance. This study improved our knowledge about the heat resistance of some spoilage microorganisms in presence of CO2.

Nitrogen and potassium limit fine root growth in a humid Afrotropical forest.

Nutrient limitations play a key regulatory role in plant growth, thereby affecting ecosystem productivity and carbon uptake. Experimental observations identifying the most limiting nutrients are lacking, particularly in Afrotropical forests. We conducted an ecosystem-scale, full factorial nitrogen (N)-phosphorus (P)-potassium (K) addition experiment consisting 32 40 × 40 m plots (eight treatments × four replicates) in Uganda to investigate which (if any) nutrient limits fine root growth. After two years of observations, added N rapidly decreased fine root biomass by up to 36% in the first and second years of the experiment. Added K decreased fine root biomass by 27% and fine root production by 30% in the second year. These rapid reductions in fine root growth highlight a scaled-back carbon investment in the costly maintenance of large fine root network as N and K limitations become alleviated. No fine root growth response to P addition was observed. Fine root turnover rate was not significantly affected by nutrient additions but tended to be higher in N added than non-N added treatments. These results suggest that N and K availability may restrict the ecosystem's capacity for CO2 assimilation, with implications for ecosystem productivity and resilience to climate change.

Artificial cellulosic leaf with adjustable enzymatic CO2 sequestration capability.

Developing artificial leaves to address the environmental burden of CO2 is pivotal for advancing our Net Zero Future. In this study, we introduce EcoLeaf, an artificial leaf that closely mimics the characteristics of natural leaves. It harnesses visible light as its sole energy source and orchestrates the controlled expansion and contraction of stomata and the exchange of petiole materials to govern the rate of CO2 sequestration from the atmosphere. Furthermore, EcoLeaf has a cellulose composition and mechanical strength similar to those of natural leaves, allowing it to seamlessly integrate into the ecosystem during use and participate in natural degradation and nutrient cycling processes at the end of its life. We propose that the carbon sequestration pathway within EcoLeaf is adaptable and can serve as a versatile biomimetic platform for diverse biogenic carbon sequestration pathways in the future.

Drawing a line from CO2 emissions to health-evaluation of medical students' knowledge and attitudes towards climate change and health following a novel serious game: a mixed-methods study.

BACKGROUND: Education is urgently needed to equip medical students with knowledge, values and skills to promote planetary health. However, the current literature offers little insight into evidence-based approaches and best practices. In response to this pressing need, a novel serious game was introduced into the medical curriculum at Erasmus Medical Center in 2023. The aim of this study was to evaluate the knowledge and attitudes of medical students after they had played a serious game that addresses climate change and health. METHODS: In accordance with a mixed-methods design, quantitative data were collected using pre- and post-intervention surveys. Differences were assessed using the Wilcoxon signed rank test. Focus group discussions were held after the game and thematically analysed. RESULTS: One hundred forty-five students (38.6% of the entire cohort) played the game, of which 59 students completed the pre- and post-intervention surveys. After the game, self-reported knowledge increased. Regarding objective knowledge, an increase in the proportion of students who answered one of the two questions correctly was observed, while the proportion of correct responses decreased for the other question. Student's responses to two out of five attitude questions were significantly more positive. The proportion of students who recognized the importance of climate change education, to inform patients and society about the health impacts of climate change, increased. Moreover, survey results indicated a significant increase in climate worry subsequent to the game. Eleven students participated in the focus group discussions. Thematic analysis highlighted participants' reflections on the roles and responsibilities in climate change and health, along with their realisation of the tools for action that climate and health co-benefits provide. Another significant aspect was the importance participants placed on learning alongside peers with diverse attitudes. Additionally, participants appreciated the tangible overview of climate change and health provided by the serious game. CONCLUSIONS: Our novel serious game addressed an important gap in the medical curriculum. The game can enable medical students to cultivate the necessary knowledge and attitudes to promote health in times of a climate crisis. The accompanying climate worry needs attention through the empowerment of students' agency to foster change.

Comparison of the Catabolic Rates of Linoleic and Oleic Acid Hydroperoxides Using 13CO2 Expired from Mice.

Unsaturated fatty acids, such as oleic and linoleic acids, are easily oxidized by exposure to temperature and light in the presence of air to form unsaturated fatty acid hydroperoxides as primary oxidation products. However, the catabolic rates of unsaturated fatty acid hydroperoxides in the human body remain unknown. In this study, ethyl esters of 13C-labeled linoleic acid (*C18:2-EE) and oleic acid (*C18:1-EE) and their hydroperoxides (*C18:2-EE-OOH and *C18:1-EE-OOH, respectively) prepared by the photo-oxidation of *C18:2-EE and *C18:1-EE, respectively, were administered to mice and their catabolic rates were determined by measuring the expired 13CO2 levels. *C18:2-EE-OOH and *C18:1-EE-OOH were ß-oxidized faster than *C18:2-EE and *C18:1-EE, respectively. Notably, rapid ß-oxidation of *C18:2-EE-OOH and *C18:1-EE-OOH was similar to that of medium-chain fatty acids, such as octanoic acid. Then, degradation products of C18:2-EE-OOH and C18:1-EE-OOH were analyzed under gastric conditions by gas chromatography/mass spectrometry. Major decomposition products of C18:2-EE-OOH and C18:1-EE-OOH were medium-chain compounds, such as octanoic acid ethyl ester, 9-oxo-nonanoic acid ethyl ester, and 10-oxo-8-decenoic acid ethyl esters, indicating that C18:2-EE-OOH and C18:1-EE-OOH isomers formed during photo-oxidation were decomposed under acidic conditions. These findings support previous reports that dietary lipid hydroperoxides are not absorbed into the intestine as lipid hydroperoxides but as degradation products. This is the first study to suggest that dietary lipid hydroperoxides decompose during gastric digestion to form medium-chain compounds that are directly absorbed into the liver via the portal vein and rapidly catabolized via ß-oxidation.

Standard vs. carbone dioxide adapted kidney replacement therapy in hypercapnic ARDS patients: a randomized controlled pilot trial (BigBIC).

BACKGROUND: Current continuous kidney replacement therapy (CKRT) protocols ignore physiological renal compensation for hypercapnia. This study aimed to explore feasibility, safety, and clinical benefits of pCO2-adapted CKRT for hypercapnic acute respiratory distress syndrome (ARDS) patients with indication for CKRT. METHODS: We enrolled mechanically ventilated hypercapnic ARDS patients (pCO2 > 7.33 kPa) receiving regional citrate anticoagulation (RCA) based CKRT in a prospective, randomized-controlled pilot-study across five intensive care units at the Charité-Universitätsmedizin Berlin, Germany. Patients were randomly assigned 1:1 to the control group with bicarbonate targeted to 24 mmol/l or pCO2-adapted-CKRT with target bicarbonate corresponding to physiological renal compensation. Study duration was six days. Primary outcome was bicarbonate after 72 h. Secondary endpoints included safety and clinical endpoints. Endpoints were assessed in all patients receiving treatment. RESULTS: From September 2021 to May 2023 40 patients (80% male) were enrolled. 19 patients were randomized to the control group, 21 patients were randomized to pCO2-adapted-CKRT. Five patients were excluded before receiving treatment: three in the control group (consent withdrawal, lack of inclusion criteria fulfillment (n = 2)) and two in the intervention group (lack of inclusion criteria fulfillment, sudden unexpected death) and were therefore not included in the analysis. Median plasma bicarbonate 72 h after randomization was significantly higher in the intervention group (30.70 mmol/l (IQR 29.48; 31.93)) than in the control group (26.40 mmol/l (IQR 25.63; 26.88); p < 0.0001). More patients in the intervention group received lung protective ventilation defined as tidal volume < 8 ml/kg predicted body weight. Thirty-day mortality was 10/16 (63%) in the control group vs. 8/19 (42%) in the intervention group (p = 0.26). CONCLUSION: Tailoring CKRT to physiological renal compensation of respiratory acidosis appears feasible and safe with the potential to improve patient care in hypercapnic ARDS. TRIAL REGISTRATION: The trial was registered in the German Clinical Trials Register (DRKS00026177) on September 9, 2021 and is now closed.

Methanol as a co-substrate with CO2 enhances butyrate production in microbial electrosynthesis.

Methanol is a promising feedstock for the bio-based economy as it can be derived from organic waste streams or produced electrochemically from CO2. Acetate production from CO2 in microbial electrosynthesis (MES) has been widely studied, while more valuable compounds such as butyrate are currently attracting attention. In this study, methanol was used as a co-substrate with CO2 to enhance butyrate production in MES. Feeding with CO2 and methanol resulted in the highest butyrate production rates and titres of 0.36 ± 0.01 g L-1 d-1 and 8.6 ± 0.2 g L-1, respectively, outperforming reactors with only CO2 feeding (0.20 ± 0.03 g L-1 d-1 and 5.2 ± 0.1 g L-1, respectively). Methanol acted as electron donor and as carbon source, both of which contributed ca. 50% of the carbon in the products. Eubacterium was the dominant genus with 52.6 ± 2.5% relative abundance. Thus, we demonstrate attractive route for the use of the C1 substrates, CO2 and methanol, to produce mainly butyrate. KEY POINTS: • Butyrate was the main product from methanol and CO2 in MES • Methanol acted as both carbon and electron source in MES • Eubacterium dominating microbial culture was enriched in MES.

Structures of wild-type and a constitutively closed mutant of connexin26 shed light on channel regulation by CO2.

Connexins allow intercellular communication by forming gap junction channels (GJCs) between juxtaposed cells. Connexin26 (Cx26) can be regulated directly by CO2. This is proposed to be mediated through carbamylation of K125. We show that mutating K125 to glutamate, mimicking the negative charge of carbamylation, causes Cx26 GJCs to be constitutively closed. Through cryo-EM we observe that the K125E mutation pushes a conformational equilibrium towards the channel having a constricted pore entrance, similar to effects seen on raising the partial pressure of CO2. In previous structures of connexins, the cytoplasmic loop, important in regulation and where K125 is located, is disordered. Through further cryo-EM studies we trap distinct states of Cx26 and observe density for the cytoplasmic loop. The interplay between the position of this loop, the conformations of the transmembrane helices and the position of the N-terminal helix, which controls the aperture to the pore, provides a mechanism for regulation.

Measurement of Photorespiratory Oxygen Exchange by Membrane Inlet Mass Spectrometry.

Photosynthesis and metabolism in plants involve oxygen as both a product and substrate. Oxygen is taken up during photorespiration and respiration and produced through water splitting during photosynthesis. To distinguish between processes that produce or consume O2 in leaves, isotope mass separation and detection by mass spectrometry allows measurement of evolution and uptake of O2 as well as CO2 uptake. This chapter describes how to calculate the rate of Rubisco oxygenation and carboxylation from in vivo gas exchange of stable isotopes of 16O2 and 18O2 with a closed cuvette system for leaf discs and membrane inlet mass spectrometry.

Low-Cost System for Maintaining Low Atmospheric CO2 Levels During Arabidopsis Cultivation.

Photosynthesis requires CO2 as the carbon source, and the levels of ambient CO2 determine the oxygenation or carboxylation of Ribulose-1,5-bisphosphate (RuBP) by RuBP carboxylase/oxygenase (Rubisco). Low CO2 levels lead to oxygenation and result in photorespiration, which ultimately causes a reduction in net carbon assimilation through photosynthesis. Therefore, an increased understanding of plant responses to low CO2 contributes to the knowledge of how plants circumvent the harmful effects of photorespiration. Methods for elevating CO2 above ambient concentrations are often achieved by external sources of CO2, but reducing CO2 below the ambient value is much more difficult as CO2 gas needs to be scrubbed from the atmosphere rather than added to it. Here, we describe a low-cost method of achieving low CO2 conditions for Arabidopsis growth.

Using Dynamic Gas Exchange Measurements During Oxygen Transients to Study Nonsteady-State Photorespiration.

Leaf-level gas exchange is widely used to investigate the largest carbon fluxes in illuminated leaves, offering a nondestructive way to investigate the impact of photorespiration on plant carbon balance. Modern commercial gas exchange systems allow high temporal resolution measurements under changing environments, aiding the development of nonsteady-state approaches for measuring dynamic photosynthetic responses. Here, we describe a nonsteady-state technique for acquiring the dynamic response of net CO2 assimilation to changes in photorespiratory fluxes manipulated by O2 mole fractions. This technique allows for the screening of plant genotypes with variations in their efficiencies of photorespiration under nonsteady-state conditions.

Analysis of Photorespiratory Intermediates Under Transient Conditions by Mass Spectrometry.

Photorespiration is an essential process of phototropic organisms caused by the limited ability of rubisco to distinguish between CO2 and O2. To understand the metabolic flux through the photorespiratory pathway, we combined a mass spectrometry-based approach with a shift experiment from elevated CO2 (3000 ppm) to ambient CO2 (390 ppm). Here, we describe a protocol for quantifying photorespiratory intermediates, starting from plant cultivation through extraction and evaluation.

Combining Gas Exchange and Rapid Quenching of Leaf Tissue for Mass Spectrometry Analysis Directly in Gas Exchange Cuvette.

Isotopically nonstationary metabolic flux analysis (INST-MFA) is a powerful technique for studying plant central metabolism, which involves introducing a 13CO2 tracer to plant leaves and sampling the labeled metabolic intermediates during the transient period before reaching an isotopic steady state. The metabolic intermediates involved in the C3 cycle have exceptionally fast turnover rates, with some intermediates turning over many times a second. As a result, it is necessary to rapidly introduce the label and then rapidly quench the plant tissue to determine concentrations in the light or capture the labeling kinetics of these intermediates at early labeling time points. Here, we describe a rapid quenching (0.1-0.5 s) system for 13CO2 labeling experiments in plant leaves to minimize metabolic changes during labeling and quenching experiments. This system is integrated into a commercially available gas exchange analyzer to measure initial rates of gas exchange, precisely control ambient conditions, and monitor the conversion from 12CO2 to 13CO2.

Using Gas Exchange to Study CO2 Release During Photosynthesis with Steady- and Nonsteady-State Approaches.

Measures of respiration in the light and Ci* are crucial to the modeling of photorespiration and photosynthesis. This chapter provides background on the equations used to model C3 photosynthesis and the history of the incorporation of the effects of rubisco oxygenation into these models. It then describes three methods used to determine two key parameters necessary to incorporate photorespiratory effects into C3 photosynthesis models: respiration in the light (RL) and Ci*. These methods include the Laisk, Yin, and isotopic methods. For the Laisk method, we also introduce a new rapid measurement technique.

Reaction-Kinetic Modeling of Photorespiration Using Modelbase.

Plant science has become more and more complex. With the introduction of new experimental techniques and technologies, it is now possible to explore the fine details of plant metabolism. Besides steady-state measurements often applied in gas-exchange or metabolomic analyses, new approaches, e.g., based on 13C labeling, are now available to understand the changes in metabolic concentrations under fluctuating environmental conditions in the field or laboratory. To explore those transient phenomena of metabolite concentrations, kinetic models are a valuable tool. In this chapter, we describe ways to implement and build kinetic models of plant metabolism with the Python software package modelbase. As an example, we use a part of the photorespiratory pathway. Moreover, we show additional functionalities of modelbase that help to explore kinetic models and thus can reveal information about a biological system that is not easily accessible to experiments. In addition, we will point to extra information on the mathematical background of kinetic models to give an impetus for further self-study.

Combining Gas Exchange and Rapid Quenching of Leaf Tissue for Mass Spectrometry and NMR Analysis Using an External Chamber.

We describe here a method to study and manipulate photorespiration in intact illuminated leaves. When the CO2/O2 mole fraction ratio changes, instant sampling is critical, to quench leaf metabolism and thus trace rapid metabolic modification due to gaseous conditions. To do so, we combine 13CO2 labeling and gas exchange, using a large custom leaf chamber to facilitate fast sampling by direct liquid nitrogen spraying. Moreover, the use of a high chamber surface area (about 130 cm2) allows one to sample a large amount of leaf material to carry out 13C-nuclear magnetic resonance (NMR) analysis and complementary analyses, such as isotopic analyses by high-resolution mass spectrometry (by both GC and LC-MS). 13C-NMR gives access to absolute 13C amounts at the specific carbon atom position in the labeled molecules and thereby provides an estimate of 13C-flux of photorespiratory intermediates. Since NMR analysis is not very sensitive and can miss minor metabolites, GC or LC-MS analyses are useful to monitor metabolites at low concentrations. Furthermore, 13C-NMR and high-resolution LC-MS allow to estimate isotopologue distribution in response to 13CO2 labeling while modifying photorespiration activity.

Can China's carbon generalized system of preferences reduce urban residents' carbon emissions? Evidence from a quasi-natural experiment.

The carbon generalized system of preferences (CGSP) is an innovative incentive mechanism implemented by the Chinese government, which has also become an important part of carbon emission reduction at the living end, and it is of great significance to study whether the Pilot Policy can reduce the carbon emissions of residents. This study firstly accounts for the total carbon emissions and per capita carbon emissions of the residents of 284 cities in China, and on this basis, adopts the SCM method to quantitatively study and analyze the overall and local implementation effects of CGSP in China by taking the first batch of CGSP pilots in China as an example, and further applies the mediation effect model to test the pathways of the role of CGSP. The main findings of the study are as follows: (1) During the period of 2010-2020, the total carbon emissions from urban residents' living in China showed a yearly growth trend, from 36,623.98 ×10-2Mt in 2010-85,241.20 ×10-2Mt in 2020, an increase of 8.83%. Total carbon emissions present a structural difference of "electricity consumption > central heating > private transport > gas (oil, natural gas) consumption". (2) Overall, the implementation of the CGSP had a robust positive impact on the overall carbon emission reduction in the pilot cities, with an average annual emission reduction effect value of 36.53 ×10-2Mt. Locally, the annual net policy effect values of Dongguan, Zhongshan, Heyuan, and Guangzhou are 6169.79 ×10-2, 26,600.17 ×10-2, 17,081.34 ×10-2 and 9393.36 ×10-2Mt respectively. (3) CGSP has a good carbon emission reduction effect by suppressing the impact on residents' carbon emissions through enhancing the city's innovation capacity and promoting electricity saving and consumption reduction, while the mediating effect played by the promotion of green and low-carbon travel in the pilot policy is not significant. Finally, based on the research findings, relevant suggestions are targeted.

Measuring and Quantifying Characteristics of the Post-illumination Burst.

Leaf-level gas exchange enables accurate measurements of net CO2 assimilation in the light, as well as CO2 respiration in the dark. Net positive CO2 assimilation in the light indicates that the gain of carbon by photosynthesis offsets the photorespiratory loss of CO2 and respiration of CO2 in the light (RL), while the CO2 respired in the dark is mainly attributed to respiration in the dark (RD). Measuring the CO2 release specifically from photorespiration in the light is challenging since net CO2 assimilation involves three concurrent processes (the velocity of rubisco carboxylation; vc, velocity of rubisco oxygenation; vo, and RL). However, by employing a rapid light-dark transient, it is possible to transiently measure some of the CO2 release from photorespiration without the background of vc-based assimilation in the dark. This method is commonly known as the post-illumination CO2 burst (PIB) and results in a "burst" of CO2 immediately after the transition to the dark. This burst can be quantitatively characterized using several approaches. Here, we describe how to set up a PIB measurement and provide some guidelines on how to analyze and interpret the data obtained using a PIB analysis application developed in R.