High CO2 Tolerance Research Articles

Species-Specific Responses of Juvenile Rockfish to Elevated pCO2: From Behavior to Genomics.

In the California Current ecosystem, global climate change is predicted to trigger large-scale changes in ocean chemistry within this century. Ocean acidification—which occurs when increased levels of atmospheric CO2 dissolve into the ocean—is one of the biggest potential threats to marine life. In a coastal upwelling system, we compared the effects of chronic exposure to low pH (elevated pCO2) at four treatment levels (i.e., pCO2 = ambient [500], moderate [750], high [1900], and extreme [2800 μatm]) on behavior, physiology, and patterns of gene expression in white muscle tissue of juvenile rockfish (genus Sebastes), integrating responses from the transcriptome to the whole organism level. Experiments were conducted simultaneously on two closely related species that both inhabit kelp forests, yet differ in early life history traits, to compare high-CO2 tolerance among species. Our findings indicate that these congeners express different sensitivities to elevated CO2 levels. Copper rockfish (S. caurinus) exhibited changes in behavioral lateralization, reduced critical swimming speed, depressed aerobic scope, changes in metabolic enzyme activity, and increases in the expression of transcription factors and regulatory genes at high pCO2 exposure. Blue rockfish (S. mystinus), in contrast, showed no significant changes in behavior, swimming physiology, or aerobic capacity, but did exhibit significant changes in the expression of muscle structural genes as a function of pCO2, indicating acclimatization potential. The capacity of long-lived, late to mature, commercially important fish to acclimatize and adapt to changing ocean chemistry over the next 50–100 years is likely dependent on species-specific physiological tolerances.

Nutrients Extracted from Chicken Manure Accelerate Growth of Microalga <i>Scenedesmus obliquus</i> HTB1

Sustainable development using wastes as resources is a new paradigm. Chicken manure contains rich amounts of nitrogen and phosphorus and has been used as crop fertilizer. However, little is known about whether nutrients of chicken manure are suitable and efficient to support the rapid growth of microalgae. In this study, we explore the possibility of using nutrient extracted from chicken manure to grow microalgae. We used an algal strain Scenedesmus sp. HTB1, which is an oleaginous species with high CO2 tolerance capability. The growth performance of HTB1 on various media amended with nutrient extracted from three different chicken manure sources was monitored and compared to the growth rate of HTB1 grown in the standard medium BG11. Meanwhile, the changes of total nitrogen (N) and phosphorus (P), both organic and inorganic, were measured during the growth period. Culture media enriched with the nutrient extracted from two chicken manure sources outperformed the standard culture medium BG11 in terms of algal biomass production. When cultivated with manure nutrient, HTB1 utilized inorganic N efficiently, but consumed very little organic N during the experimental growth period. However, HTB1 was able to utilize both organic and inorganic phosphorus. We demonstrate that nutrient extracted from chicken manure support rapid growth and high biomass yield in microalgae Scenedesmus obliquus HTB1. Therefore chicken manure holds great promise to be used as a cost-effective and efficient fertilizer for large-scale production of microalgae.

Highly oxygen-permeable and CO2-stable Ce0.8Sm0.2O2 − δ-SrCo0.9Nb0.1O3 − δ dual-phase membrane for oxygen separation

Dual-phase composite oxide 60wt% Ce0.8Sm0.2O2−δ-40wt% SrCo0.9Nb0.1O3−δ (60SDC-40SCN) which exhibits high oxygen permeability and good CO2 tolerance was developed. X-ray diffraction (XRD) patterns and dense surface topography observed by scanning electron microscopy (SEM) revealed a good compatibility of the two oxides. A high oxygen permeation flux of 1.54mLmin−1cm−2 through the as-prepared dual-phase membrane (0.8mm in thickness) was obtained under the gradient of air/He at 1223K. In situ high-temperature X-ray diffraction demonstrated that SDC and SCN in 60SDC-40SCN membrane could retain their original phase structure from room temperature to 1223K in CO2-containing atmosphere. The oxygen permeation fluxes of 60SDC-40SCN membrane showed a good reversibility when switching the sweep gas between CO2 and He. Comparing with single-phase SCN membrane, oxygen permeation flux of dual-phase 60SDC-40SCN membrane was more than twice when pure CO2 acted as the sweep gas, and the oxygen permeation flux could remain stable for 120h. All the experimental results imply that dual-phase 60SDC-40SCN membrane has a great potential in oxy-fuel combustion process.

Characterization of a microalgal mutant for CO2 biofixation and biofuel production

In the present work, a Chlorella vulgaris mutant, named as SDEC-3M, was screened out through the combination of the isolation using 96-well microplates and traditional UV mutagenesis. Compared with its parent (wild type), the growth of SDEC-3M preferred higher CO2 (15% v/v) environment to ambient air (0.038% CO2 (v/v)), indicating that the mutant qualified with good tolerance and growth potential under high level CO2 (high CO2 tolerance) but was defective in directly utilizing the low level CO2 (high CO2 requiring). The genetic stability under ambient air and high level CO2 was confirmed by a continuous cultivation for five generations. Higher light conversion efficiency (14.52%) and richer total carbohydrate content (42.48%) demonstrated that both solar energy and CO2 were more effectively productively fixed into carbohydrates for bioethanol production than the parent strain. The mutant would benefit CO2 biofixation from industrial exhaust gas to mitigate of global warming and promote biofuel production to relieve energy shortage.

Identification of Potential Culture Conditions for Enhancing the Biomass Production of Microalga Chlorella minutissima

Identification of Potential Culture Conditions for Enhancing the Biomass Production of Microalga Chlorella minutissima Microalgae have been considered as appropriate source of various commercial products due to their enormous potential of growth, higher content of biochemical product like sugars, lipids, proteins and pigments, high CO2 tolerance etc. But these organisms are easily affected by environmental factors due to their minute size. So it is necessary to find potential culture conditions of microalgae so maximum biomass can be achieved in short duration of time under lab settings. In this study, effects of various components of culture conditions on biomass of microalga Chlorella minutissima were recorded. Based on the result of biomass production, potential culture conditions have been summarized for microalgae Chlorella minutissima. Among six different media tested, N-11, BBM and BG-11 media were found suitable for this microalga. Although with nitrogen starvation, BBM and BG-11 were found to be the potential media. Potential source of nitrogen, phosphorus and carbon were sodium & potassium nitrate, di-potassium hydrogen phosphate & potassium di hydrogen phosphate and glycerol respectively. The suitable concentration of nitrate, phosphate, and glycerol were 0.375 g/l, 0.16 g/l and 12.5 g/l. Alkaline pH was found suitable for this microalgae to provide higher biomass. Chlorella minutissima has shown better biomass production in 24 hours of illumination of white light of 20 W tube light and shaking period of 2 hours in Erlenmeyer flasks.

Effects of WO3 doping on stability and N2O escape of MnOx–CeO2 mixed oxides as a low-temperature SCR catalyst

MnOx–WOx–CeO2 catalysts synthesized using a sol–gel method were investigated for the low-temperature NH3-SCR reaction. Among them, W0.1Mn0.4Ce0.5 mixed oxides exhibited above 80% NOx conversion from 140 to 300°C. In addition, this catalyst exhibited high stability and CO2 tolerance in a 50h activity test at 150°C. Substantially reduced N2O production and enhanced N2 selectivity were achieved by WO3 doping, which was due to the weakened reducibility and increased number of acid sites. The decreased SO2 oxidation activity as well as the reduced formation of ammonium and manganese sulfates resulted in a high SO2 resistance of this catalyst.

Cobalt-free SrFe0.9Ti0.1O3−δ as a high-performance electrode material for oxygen reduction reaction on doped ceria electrolyte with favorable CO2 tolerance

A cobalt-free titanium-doped SrFeO3−δ perovskite with a nominal composition of SrFe0.9Ti0.1O3−δ (SFT) is exploited as an alternative electrode for solid oxide fuel cells (SOFCs). Special attention is given to the effects of CO2 on the oxygen reduction reaction (ORR) performance and properties of the oxide. For this investigation, XRD, HR-TEM, FT-IR, 4-probe DC conductivity, EIS and SEM are used. Although no bulk carbonate is formed, even under a pure CO2 atmosphere, the chemical adsorption of CO2 only appears over the SFT surface, which suggests a weak effect of CO2 on the structure of SFT. The EIS tests demonstrate that such CO2 adsorption does have a modest and detrimental effect on the ORR over the SFT electrode. However, the electrochemical performance can be easily recovered after removing of CO2. Thus, SrFe0.9Ti0.1O3−δ is a promising cathode material for practical SOFCs due to its high activity, high CO2 tolerance, and low cost.

Improving high carbon dioxide tolerance and carbon dioxide fixation capability of Chlorella sp. by adaptive laboratory evolution

CO2 capture by microalgae is a promising method to reduce greenhouse gas emissions. It is critical to construct a highly efficient way to obtain a microalgal strain tolerant to high CO2 concentrations with high CO2 fixation capability. In this study, two evolved Chlorella sp. strains, AE10 and AE20 were obtained after 31 cycles of adaptive laboratory evolution (ALE) under 10% and 20% CO2, respectively. Both of them grew rapidly in 30% CO2 and the maximal biomass concentration of AE10 was 3.68±0.08g/L, which was 1.22 and 2.94 times to those of AE20 and original strain, respectively. The chlorophyll contents of AE10 and AE20 were significantly higher than those of the original one under 1–30% CO2. The influences of ALE process on biochemical compositions of Chlorella cells were also investigated. This study proved that ALE was an effective approach to improve high CO2 tolerance of Chlorella sp.

Desmodesmus sp. 3Dp86E-1-a novel symbiotic chlorophyte capable of growth on pure CO2.

A novel chlorophyte Desmodesmus sp. 3Dp86E-1 isolated from a White Sea hydroid Dynamena pumila was cultivated at CO2 levels from atmospheric (the 'low-CO2' conditions) to pure carbon dioxide (the 5, 20, and 100% CO2 conditions) under high (480μE/(m(2)s) PAR) light. After 7days of cultivation, the '100% CO2' (but not 5 or 20% CO2) cells possessed ca. four times higher chlorophyll content per dry weight (DW) unit than the low-CO2 culture. The rate of CO2 fixation under 100% CO2 comprised ca. 1.5L/dayperL culture volume. After a lag period which depended on the CO2 level, biomass accumulation and volumetric fatty acid (FA) content of the Desmodesmus sp. 3Dp86E-1 bubbled with CO2-enriched gas mixtures increased and was comparable to that of the culture continuously bubbled with air. Under the low-to-moderate CO2 conditions, the FA percentage of the algal cells increased (to 40% DW) whereas under high-CO2 conditions, FA percentage did not exceed 15% DW. A strong increase in oleate (18:1) proportion of total FA at the expense of linolenate (18:3) was recorded in the '100% CO2' cells. Electron microscopy and pulse-amplitude-modulated chlorophyll fluorescence investigation revealed no damage to or significant downregulation of the photosynthetic apparatus in '100% CO2' cells grown at the high-PAR irradiance. Possible mechanisms of high-CO2 tolerance of Desmodesmus sp. 3Dp86E-1 are discussed in view of its symbiotic origin and possible application for CO2 biomitigation.

Operational Strategies for Lab scale Horizontal Tubular Photobioreactor for Mitigation of CO2 Using an Indigenous Thermophilic Microalgal Strain Geitlerinema sulphureum

Anthropogenic activities leading to the industrial revolution have contributed substantially to climate change by adding carbon dioxide (CO2) into the atmosphere which has caused a gradual but significant increase in the atmospheric temperature through the years. Part of the efforts to mitigate CO2 involves the capture and sequestration using microalgae. Efforts were made in KET’s VG Vaze College to screen indigenously isolated thermophilic cyanobacteria for this purpose. High temperature adaptability (42oC), high CO2 tolerance (23.08%), reasonably high biomass production and easy harvesting made G. sulphureum a promising candidate for the CO2 sequestration in the tropical climatic conditions. The present communication deals with the optimisation of productivity of G. sulphureum in a lab scale tubular photobioreactor by altering paramters such as light regime, CO2 supplementation, and nitrate and carbon source optimisation. The baseline productivity was 0.035 g/Lday before optimisation. In case of the cumulatively optimised productivity, it increased to 0.094 g/Lday with the highest reported biomass concentration of 1.29 g/L.

High-CO2 tolerance in microalgae: possible mechanisms and implications for biotechnology and bioremediation

Recent developments in the field of microalgal biotechnology, including CO2 biomitigation and the discovery of new species of microalgae that are tolerant to extremely high CO2 levels (40-100 vol%), have renewed interest in the physiological effects and mechanisms of high-CO2 tolerance in photoautotrophs. Photosynthetic apparatus state transitions that increase ATP generation, upregulation of H(+)-ATPases pumping protons out of the cell, rapid shutdown of CO2-concentrating mechanisms, and adjustment of membranes' fatty acid composition are currently believed to be the key mechanisms governing cellular pH homeostasis and hence microalgae's tolerance to high CO2 levels, which is especially characteristic of extremophile and symbiotic species. The mechanisms governing acclimation to high CO2 comprise the subject of this review and are discussed in view of the use of CO2 enrichment to increase the productivity of microalgal cultures, as well as the practice of carbon capture from flue gases.

CO preferential oxidation in H2-rich stream over a CuO/CeO2 catalyst with high H2O and CO2 tolerance

The CuO/CeO2 catalysts are prepared by an improved incipient wetness impregnation method with ammonia as chelating agent for CO preferential oxidation (PROX). The effects of CuO loadings of the catalysts and the presence of H2O and CO2 in the reaction stream on the catalytic performance are investigated. The CuO/CeO2 catalyst with 10.0wt.% CuO loading has high activity and stability for the CO-PROX. In the long-term stability test under the realistic reaction condition with 10% H2O and 15% CO2 in the reactant stream, 100% CO conversion can maintain for 1600h at 140–150°C with 85–75% selectivity. The catalysts are characterized by means of XRD, H2-TPR, and CO-TPR. The results show that the high activity of the CuO/CeO2 catalyst is closely related to the fine-dispersed CuO species strongly interacting with CeO2 support.

Isolation and determination of cultural characteristics of a new highly CO2 tolerant fresh water microalgae

Fresh water microalgae, which has high CO2 tolerance, were isolated and its cultural characteristics were investigated. The ZY-1 strain was identified as genus Chlorella. It showed maximum growth at 10% (v/v) CO2 enriched air flowing condition, and a good growth rate in a broad range of physically controllable conditions, including CO2 concentration up to 70% (v/v), CO2 enriched air flow rate, temperature and pH value. The results indicated the feasibility of the ZY-1 strain for fixing CO2 from stack gases.

EVALUATION OF THE PHYSIOLOGICAL RESPONSE OF SHREDDED GALEGA KALE UNDER LOW OXYGEN AND HIGH CARBON DIOXIDE CONCENTRATIONS

The high perishability of fresh-cut products requires the use of preservation techniques along the distribution chain. Refrigeration and modified atmosphere packaging (MAP) are important postharvest techniques in the extension of produce shelf life. Shredded Galega kale (Brassica oleracea var. acephala) is a fresh-cut vegetable of special interest in the Portuguese market. Potential benefits and risks of low O2 and high CO2 concentrations in fresh shredded Galega kale should be addressed before the commercial application of MAP. Respiration rate, sensory attributes, and colour alterations, in addition to water, chlorophyll, and ascorbic acid contents were monitored in shredded Galega kale during storage at 20 °C under different atmospheres. Low O2 tolerance (1, 2, 3 or 21% v/v O2 without CO2) was tested and it was concluded that quality retention improved with reduced O2 concentration and no induction of anaerobic respiration was detected. High CO2 tolerance (0, 10, 15, or 20% v/v CO2 plus 21% v/v O2) was also tested. Storage under high CO2 concentration extended the product shelf life and no symptoms of CO2 injury were detected. Finally, combinations of low O2 and high CO2 (1 or 2% v/v O2 plus 15 or 20% v/v CO2 and air as control) were analysed. No differences were observed among the different concentrations tested in this range. An atmosphere of 1-2% v/v O2 plus 15-20% v/v CO2 will extend the shelf life of shredded Galega kale at 20 °C to 4 days, compared to 2 days in air storage. OBJECTIVES The selection of concentrations of O2 and CO2 that prolong the shelf life of a given fresh product is essential to design a successful MAP system. No research has yet demonstrated a beneficial effect of reduced O2 and elevated CO2 on fresh shredded Galega kale quality. The specific objectives of this work were: i) to evaluate the tolerance of fresh shredded Galega kale to low O2 levels and to high CO2 levels, and ii) to identify a range of O2 and CO2 adequate for MAP of this product.

Relationship between oxygen-evolution and hydrogen-evolution in a Chlorococcum strain with high CO 2-tolerance

The relationship between photosynthesis and photohydrogen evolution was investigated in a highly CO 2-tolerant strain of Chlorococcum littorale. Concentrations of 0.03% to 40% CO 2 were applied during growth of the cells. A concentraction of 5% CO 2 is the most favourable condition for growth, pigment formation and carbohydrate formation, all of which tail off towards a concentration of 40% CO 2. The same pattern was observed for oxygen evolution and photohydrogen evolution. The reason for the decline at high CO 2 concentrations was found in the partial inhibition of photosystem II (PS II). The initial rates of photohydrogen evolution were at least double those of O 2 evolution, demonstrating the higher affinity of the hydrogenase than the NADP-reductase to the electrons provided by the photosynthetic electron transport chain. CO 2 concentration had no influence on the in vitro activity of the hydrogenase.