光驱动二氧化碳转化系统的构建、优化与应用

利用光能驱动二氧化碳(carbon dioxide, CO₂)还原生产化学品对于缓解环境压力、解决能源危机具有重要意义。光捕获、光电转化和CO₂固定等作为影响光合作用效率的关键因素,同时也制约着CO₂的资源化利用效率。为了解决上述问题,本文从生物化学与代谢工程相结合的角度,系统总结了光驱动杂合系统的构建、优化与应用,并从酶杂合系统、生物杂合系统以及杂合系统应用3个方面分析了光驱动CO₂还原合成化学品的最新研究进展。在酶杂合系统方面,采用的策略主要有提升酶催化活性、增强酶稳定性等;在生物杂合系统方面,采用的方法主要包括增强生物捕光能力、优化还原力供应以及改善能量再生等;在杂合系统应用方面,主要阐述了光驱动CO₂还原生产一碳含能化合物、生物燃料以及生物食品等。最后,从纳米材料(包括有机材料和无机材料)和生物催化剂(包括酶和微生物)两个方面,展望了人工光合系统的进一步发展方向。     

微藻固定CO2研究进展

空气中CO₂ 浓度升高所导致的温室效应已成为重大的环境问题 ,受到人们普遍关注。概述了高效固定CO₂ 微藻藻种的筛选和培养方法 ,分析了微藻固定CO₂ 的无机碳利用形式和浓缩机制 ,讨论了高效光生物反应器设计和运行目标 ,简要介绍了微藻 (酶 ) 膜生物反应器集成新技术。并认为今后的研究方向主要是在进一步探索微藻固定CO₂ 有关机理的基础上 ,构建高效固定CO₂ 的转基因微藻 ,开发高效膜生物反应集成系统。     

电-氢-糖循环的新能源体系研究进展

发展绿色低碳的可再生能源体系已经成为重要的国际共识和方向,也是我国践行“双碳”目标、保障能源安全、走社会可持续发展的必要路径。本文聚焦电-氢-糖(electricity-hydrogen-carbohydrate, EHC)循环的新能源理论体系,重点综述了中国科学院天津工业生物技术研究所10余年来在基于体外多酶催化系统(in vitro synthetic enzymatic biosystem, ivSEB)的糖与水反应制氢、糖完全氧化产电,以及氢或电能固定CO₂到糖的生物转化方面所做的工作,阐述体外多酶催化系统的设计原则、分子基础,并从电-氢-糖循环进一步延伸出以糖(淀粉)为核心的体外合成生物制造,结合最新相关研究进展,分析讨论体外多酶催化体系的特色和优缺点,并展望未来发展方向,促进经济和社会的绿色低碳可持续发展。     

页岩气开采与深地微生物的相互影响

页岩气是一种特殊的天然气聚集,以吸附或游离状态存在于页岩之中。页岩气资源储量丰富,约占全球天然气能源的三分之一,主要分布在中国、北美、俄罗斯等国家和地区。页岩气开采所使用的水力压裂技术会对深地微生物产生显著影响,在水力压裂的不同阶段,微生物群落组成存在明显差异。其中,产甲烷菌能够提高页岩气的产量,而产酸细菌会造成设备腐蚀,降低页岩气的回收效率。本文概述了页岩气的开采现状、开采过程以及微生物种群的变化和潜在影响,以期促进页岩气开采与深地微生物相互影响的研究,最终推动页岩气的绿色、高效开采。     

岩溶区土壤微生物驱动的自养固碳过程与机制研究进展

自养微生物能够利用无机碳作为碳源合成自身营养物质,具有很强的环境适应能力,在富钙偏碱的岩溶区土壤的碳固定过程中扮演重要角色.本文综述了土壤微生物驱动的自养固碳过程、岩溶区土壤固碳功能微生物、自养固碳的分子机制及其产生的生态环境效应,并提出了亟待解决的关键科学问题.为深入研究和认识岩溶区土壤生态系统自养微生物驱动的固碳过...     

Interactions between carbon dioxide and oxygen in the photosynthesis of three species of marine red macroalgae

Summary

Red algae have the highest known selectivity factor (S_rel) for CO₂ over O₂ of ribulose bisphosphate carboxylase-oxygenase (RUBISCO). This allows the prediction that a red alga relying on diffusive supply of CO₂ to RUBISCO from air-equilibrated solution should have less O₂ inhibition of photosynthesis than would an otherwise similar non-red alga with a lower S_rel of RUBISCO. Furthermore, RUBISCO shows an increased S_rel values at low temperatures. The prediction that O ₂inhibition of photosynthesis should be small for marine red algae relying on diffusive CO₂ entry growing in the North Sea with an annual temperature range of 4–16°C was tested in O₂ electrode experiments at 12°C. Phycodrys rubens and Plocamium cartilagineum, which rely on diffusive CO₂ entry showed, as predicted, only a small inhibition at lower inorganic C concentrations. Palmaria palmata, which has a CO₂ concentrating mechanism, had the expected negligible O ₂ inhibition of photosynthesis at any inorganic C concentration except (non-significantly) for saturating inorganic C.     

Legume presence increases photosynthesis and N concentrations of co-occurring non-fixers but does not modulate their responsiveness to carbon dioxide enrichment

Legumes, with the ability to fix atmospheric nitrogen (N), may help alleviate the N limitations thought to constrain plant community response to elevated concentrations of atmospheric carbon dioxide (CO₂). To address this issue we assessed: (1) the effects of the presence of the perennial grassland N₂ fixer, Lupinus perennis, on biomass accumulation and plant N concentrations of nine-species plots of differing plant composition; (2) leaf-level physiology of co-occurring non-fixing species (Achillea millefolium, Agropyron repens, Koeleria cristata) in these assemblages with and without Lupinus; (3) the effects of elevated CO₂ on Lupinus growth and symbiotic N₂ fixation in both monoculture and the nine-species assemblages; and (4) whether assemblages containing Lupinus exhibit larger physiological and growth responses to elevated CO₂ than those without. This study was part of a long-term grassland field experiment (BioCON) that controls atmospheric CO₂ at current ambient and elevated (560 µmol mol^–1) concentrations using free-air CO₂ enrichment. Nine-species plots with Lupinus had 32% higher whole plot plant N concentrations and 26% higher total plant N pools than those without Lupinus, based on both above and belowground measurements. Co-occurring non-fixer leaf N concentrations increased 22% and mass-based net photosynthetic rates increased 41% in plots containing Lupinus compared to those without. With CO₂ enrichment, Lupinus monocultures accumulated 32% more biomass and increased the proportion of N derived from fixation from 44% to 57%. In nine-species assemblages, Lupinus N derived from fixation increased similarly from 43% to 54%. Although Lupinus presence enhanced photosynthetic rates and leaf N concentrations of co-occurring non-fixers, and increased overall plant N pools, Lupinus presence did not facilitate stronger photosynthetic responses of non-fixing species or larger growth responses of overall plant communities to elevated CO₂. Non-fixer leaf N concentrations declined similarly in response to elevated CO₂ with and without Lupinus present and the relationship between net photosynthesis and leaf N was not affected by Lupinus presence. Regardless of the presence or absence of Lupinus, CO₂ enrichment resulted in reduced leaf N concentrations and rates of net photosynthesis.     

Nitrogen deposition and carbon sequestration in alpine meadows

Nitrogen deposition experiments were carried out in alpine meadow ecosystems in Qinghai-Xizang Plateau in China, in order to explore the contribution of nitrogen deposition to carbon sequestration in alpine meadows. Two methods were used in this respect. First, we used the allocation of ¹⁵N tracer to soil and plant pools. Second, we used increased root biomass observed in the nitrogen-amended plots. Calculating enhanced carbon storage, we considered the net soil CO₂ emissions exposed to nitrogen deposition in alpine meadows. Our results show that nitrogen deposition can enhance the net soil CO₂ emissions, and thus offset part of carbon uptake by vegetation and soils. It means that we have to be cautious to draw a conclusion when we estimate the contribution of nitrogen deposition to carbon sequestration based on the partitioning of ¹⁵N tracer in terrestrial ecosystems, in particular in N-limited ecosystems. Even if we assess the contribution of nitrogen deposition to carbon sequestration based on increased biomass exposed to nitrogen deposition in terrestrial ecosystems, likewise, we have to consider the effects of nitrogen deposition on the soil CO₂ emissions.     

Non-phototrophic CO 2 fixation by soil microorganisms

Although soils are generally known to be a net source of CO₂ due to microbial respiration, CO₂ fixation may also be an important process. The non-phototrophic fixation of CO₂ was investigated in a tracer experiment with ¹⁴CO₂ in order to obtain information about the extent and the mechanisms of this process. Soils were incubated for up to 91 days in the dark. In three independent incubation experiments, a significant transfer of radioactivity from ¹⁴CO₂ to soil organic matter was observed. The process was related to microbial activity and could be enhanced by the addition of readily available substrates such as acetate. CO₂ fixation exhibited biphasic kinetics and was linearly related to respiration during the first phase of incubation (about 20–40 days). The fixation amounted to 3–5% of the net respiration. After this phase, the CO₂ fixation decreased to 1–2% of the respiration. The amount of carbon fixed by an agricultural soil corresponded to 0.05% of the organic carbon present in the soil at the beginning of the experiment, and virtually all of the fixed CO₂ was converted to organic compounds. Many autotrophic and heterotrophic biochemical processes result in the fixation of CO₂. However, the enhancement of the fixation by addition of readily available substrates and the linear correlation with respiration suggested that the process is mainly driven by aerobic heterotrophic microorganisms. We conclude that heterotrophic CO₂ fixation represents a significant factor of microbial activity in soils.     

Effect of carbon dioxide concentration on microbial respiration in soil

In order to assess the validity of conventional methods for measuring CO₂ flux from soil, the relationship between soil microbial respiration and ambient CO₂ concentration was studied using an open-flow infra-red gas analyser (IRGA) method. Andosol from an upland field in central Japan was used as a soil sample. Soil microbial respiration activity was depressed with the increase of CO₂ concentration in ventilated air from 0 to 1000 ppmv. At 1000 ppmv, the respiration rate was less than half of that at 0 ppmv. Thus, it is likely that soil respiration rate is overestimated by the alkali absorption method, because CO₂ concentration in the absorption chamber is much lower than the normal level. Metabolic responses to CO₂ concentration were different among groups of soil microorganisms. The bacteria actinomycetes group cultivated on agar medium showed a more sensitive response to the CO₂ concentration than the filamentous fungi group.     

Massive light-dependent cycling of inorganic carbon between oxygenic photosynthetic microorganisms and their surroundings

Membrane inlet mass spectrometry indicated massive light-dependent cycling of inorganic carbon between the medium and the cells of various phytoplankton species representing the main groups of aquatic primary producers. These included diatoms, symbiotic and free living dinoflagellates, a coccolithophorid, a green alga and filamentous and single cell cyanobacteria. These organisms could maintain an ambient CO₂ concentration substantially above or below that expected at chemical equilibrium with HCO₃ ⁻. The coccolithophorid Emiliania huxleyishifted from net CO₂ uptake to net CO₂ efflux with rising light intensity. Differing responses of CO₂ uptake and CO₂ fixation to changing light intensity supported the notion that these two processes are not compulsorily linked. Simultaneous measurements of CO₂ and O₂ exchange and of the fluorescence parameters in Synechococcus sp. strain PCC 7942, showed that CO₂ uptake can serve as a sensitive probe of the energy status of the photosynthetic reaction centers. However, during transitions in light intensity, changes in CO₂ uptake did not accord with those expected from fluorescence change. Quantification of the net fluxes of CO₂, HCO₃ ⁻ and of photosynthesis at steady-state revealed that substantial HCO₃ ⁻ efflux accompanied CO₂ uptake and fixation in the case of `CO<sub>2</sub> users'. On the other hand, `HCO₃ ⁻ users' were characterized by a rate of net CO₂ uptake below that of CO₂ fixation. The results support the notion that entities associated with the CCM function not only in raising the CO₂ concentration at the site of Rubisco; they may also serve as a means of diminishing photodynamic damage by dissipating excess light energy. This revised version was published online in August 2006 with corrections to the Cover Date.     

Atherosclerosis: the carbonic anhydrase, carbon dioxide, calcium concerted theory

Atherosclerosis is a dynamic multifaceted disease which affects the aorta and its major branches, characterized by the presence of lesions called atheromatous plaques. The plaque is a focal thickening of the intima caused by proliferation of smooth muscle cells, and the deposition of cholesterol, other lipids, hydroxyapatite and fibrous connective tissue. It is proposed that the determinant step of the process which leads to the disease atherosclerosis is the calcium precipitation which traps cholesterol in the plaque precursor matrix which contains lipoproteins, calcium carbonate, hydroxyapapatite, triglycerides, albumin, calmodulin and other proteins. The bear, a species which does not contract the disease is used as an example in support of the hypothesis. The bear's ability to regulate calcium levels and the regulation of acid base balance via regulation of carbon dioxide levels permits the control of the determinant step of plaque formation, that is calcification of the plaque.