利用微藻固定CO2实现碳减排的研究进展

CO2减排是目前社会经济发展所面临的重大环境问题之一,如何高效、绿色地进行减排已成为各国科研工作者关注与研究的热点。利用微藻技术进行减排符合碳循环规律,显示出很好的应用前景。本文结合笔者近年在利用微藻技术进行碳减排方面的研究工作,从固定CO2的微藻选育、微藻的培养、微藻减排在光生物反应器方面的开发以及CO2减排与污水深度处理及高价值生物质生产的耦合等4个方面对近些年来国内外在利用微藻技术实现CO2减排方面的研究情况进行了归纳与评述,并对前景进行了展望。     

微生物固碳的电子供给策略研究进展北大核心CSCD

随着生物化工技术的不断发展成熟,通过改造微生物已可以实现二氧化碳、甲烷等温室气体的固定、转化和利用,而电子传递及能量供给对微生物固碳效率起着决定性的作用。本文首先分析了好氧性嗜甲烷菌、化能自养微生物等天然微生物细胞内外的直接、间接电子传递系统。在此基础上,围绕微生物固碳细胞工厂的构建,进一步介绍了基于光能、电能的人工电子供给策略及其对固碳过程中代谢通量、合成路径和供能效率的影响。最后针对微生物固碳的关键共性技术难点,简要展望了可行性的解决方案及相关应用前景。     

Bioprocess strategies for enhancing biomolecules productivity in Chlorella fusca LEB 111 using CO2 a carbon source

The aim of this study was to evaluate the influence of different carbon dioxide (CO₂) concentrations on the distribution of carbon forms in the culture medium and the biomass production and biomolecules productivity of the strain Chlorella fusca LEB 111. In this study, experiments were carried out in which C. fusca cultures were exposed to different CO₂ concentrations, 0.03% (0.08 ml_CO2 ml_medium⁻¹ days⁻¹), 5% (0.18 ml_CO2 ml_medium⁻¹ days⁻¹), and 15% vol/vol CO₂ (0.54 ml_CO2 ml_medium⁻¹ days⁻¹). Among the carbon chemical species distributions in the culture medium, bicarbonate was predominant (94.2–98.9%), with the highest quantitative percentage in the experiment receiving a 15% CO₂ injection. C. fusca LEB 111 cultivated with 15% CO₂ showed the highest biomass productivity (194.3 mg L⁻¹ days⁻¹) and CO₂ fixation rate (390.9 mg L⁻¹ days⁻¹). The carbohydrate productivity in the culture that received 15% CO₂ was 46.2% higher than the value verified for the culture with the addition of CO₂ from the air (0.03% CO₂). In addition, CO₂ concentration providing increases of 0.03–15% to C. fusca cultures resulted in a 31.6% increase in the lipid productivity. These results showed that C. fusca can be used for CO₂ bioconversion and for producing biomass with potential applications for biofuels and bioproducts.     

Modeling and experimental validation of carbon dioxide evolution in alkalophilic cultures

The chemical reactions involving carbon dioxide in mineral culture media are considered. A mathematic model is set up, based on published data, which is valid at pH values below 9, and in which the nonideality of the solution is taken into account. The crucial parameter is the constant expressing the equilibrium between carbon dioxide and bicarbonate, K(1).The reactions were studied in three different aqueous solutions: water, mineral salt medium, and a suspension with nongrowing bacterial cells. For each situation, three methods were compared for the determination of the bicarbonate concentration in the solution: equilibrium state total carbon analysis, dynamic monitoring of the rate of acid or alkali addition, and dynamic measurement of the carbon dioxide gas phase mole fraction.In a batch-stirred tank reactor, the equilibrium constant K(1) agreed with the published value, and the three bicarbonate analysis methods give the same results. If the nonideality is not taken into account, the result significantly differed from the published value and is likely to be incorrect.A real alkalophilic process, using Acinetobacter calcoaceticus in a continuous stirred tank reactor at steady state, also gave results that are in accord with the literature. However, the results do not allow validation of the equation expressing the nonideality.The steady state in the batch system and in continuous culture can be well described with the mathematical model. However, in the transient state there are some unexplained differences between simulation and measurement.     

Response of soil carbon dioxide fluxes,soil organic carbon and microbial biomass carbon to biochar amendment: a meta‐analysis

Biochar as a carbon‐rich coproduct of pyrolyzing biomass, its amendment has been advocated as a potential strategy to soil carbon (C) sequestration. Updated data derived from 50 papers with 395 paired observations were reviewed using meta‐analysis procedures to examine responses of soil carbon dioxide (CO₂) fluxes, soil organic C (SOC), and soil microbial biomass C (MBC) contents to biochar amendment. When averaged across all studies, biochar amendment had no significant effect on soil CO₂ fluxes, but it significantly enhanced SOC content by 40% and MBC content by 18%. A positive response of soil CO₂ fluxes to biochar amendment was found in rice paddies, laboratory incubation studies, soils without vegetation, and unfertilized soils. Biochar amendment significantly increased soil MBC content in field studies, N‐fertilized soils, and soils with vegetation. Enhancement of SOC content following biochar amendment was the greatest in rice paddies among different land‐use types. Responses of soil CO₂ fluxes and MBC to biochar amendment varied with soil texture and pH. The use of biochar in combination with synthetic N fertilizer and waste compost fertilizer led to the greatest increases in soil CO₂ fluxes and MBC content, respectively. Both soil CO₂ fluxes and MBC responses to biochar amendment decreased with biochar application rate, pyrolysis temperature, or C/N ratio of biochar, while each increased SOC content enhancement. Among different biochar feedstock sources, positive responses of soil CO₂ fluxes and MBC were the highest for manure and crop residue feedstock sources, respectively. Soil CO₂ flux responses to biochar amendment decreased with pH of biochar, while biochars with pH of 8.1–9.0 had the greatest enhancement of SOC and MBC contents. Therefore, soil properties, land‐use type, agricultural practice, and biochar characteristics should be taken into account to assess the practical potential of biochar for mitigating climate change.     

Influence of power supply in the feasibility of Phaeodactylum tricornutum cultures

The influence of fluid-dynamic conditions on the yield of Phaeodactylum tricornutum microalgal cultures was analyzed in two stages: first, the influence of air flow rate; second, the influence of using fluid-moving pumps for recirculating the culture. With respect to the air flow rate, the yield of the cultures increased with the aeration rate up to values of 2.0 v/v/min, then stress was observed and the yield of the cultures decreased. With respect to the influence of mechanical power supply for liquid impulsion, three different types of pumps--centrifugal, pulse, and peristaltic--were essayed at different power supplies. The cultures were stressed for the three types of pumps essayed. For each pump, the higher the power supply the lower was the Fv/Fm value and the higher was the stress at which cells were exposed. The highest measured stress was when the culture was moved with the centrifugal pump. Despite measured stress, for all the experiments stable steady states were reached, thus indicating that cells reduced their yield but did not die, as was verified by cell viability measurements. It was observed that the increase of the power supply improved the frequency of light exposition thus enhancing the yield of the cultures. However, the higher the power supply, the lower the microeddy length scale; therefore, stress could appear. Data demonstrated that the microeddy length scale was always much higher than cell size and therefore the turbulence was not responsible for stress. Also, the mass transfer was discarded as responsible for yield reduction. It was concluded that the shear rate was the factor determining the existence of stress phenomena. The evaluation of these shear rates demonstrated that values above 30-80 s(-1) damaged the cells strongly. These data were verified in an outdoor pilot-scale tubular photobioreactor that was implemented with the same type of pumps, thus demonstrating the necessity to take into account this factor in the design and scale-up of microalgal photobioreactors.     

Observations on carbon dioxide fixation in the Nant-y-moch reservoir,Ceredigion, Wales

High rates of carbon dioxide fixation, both in the light and the dark have been observed in Nant-y-Moch Mountain reservoir; these are surprising because of the sparse algal population. The values of CO₂-carbon fixed in the light per milligramme of Chlorophyll a per hour, ranged from 0.1167 mgC/ mg Chl a/hr. to infinity and are much higher than any recorded previously. The uptake of ¹⁴C-sucrose and ¹⁴C glucose was also determined. Factors which might possibly account for these observations, either alone or in combination are discussed. Possible CO₂ fixing agencies include detritus, flagellates and other organisms capable of obtaining energy by dark reactions (chemotrophs).     

Effects of mycorrhizal colonization on biomass production and nitrogen fixation of black locust (Robinia pseudoacacia) seedlings grown under elevated atmospheric carbon dioxide

Interactive effects of elevated atmospheric CO₂ and arbuscular mycorrhizal (AM) fungi on biomass production and N₂ fixation were investigated using black locust ( Robinia pseudoacacia ). Seedlings were grown in growth chambers maintained at either 350 μmol mol⁻¹ or 710 μmol mol⁻¹ CO₂. Seedlings were inoculated with Rhizobium spp. and were grown with or without AM fungi. The ¹⁵N isotope dilution method was used to determine N source partitioning between N₂ fixation and inorganic fertilizer uptake. Elevated atmospheric CO₂ significantly increased the percentage of fine roots that were colonized by AM fungi. Mycorrhizal seedlings grown under elevated CO₂ had the greatest overall plant biomass production, nodulation, N and P content, and root N absorption. Additionally, elevated CO₂ levels enhanced nodule and root mass production, as well as N₂ fixation rates, of non- mycorrhizal seedlings. However, the relative response of biomass production to CO₂ enrichment was greater in non-mycorrhizal seedlings than in mycorrhizal seedlings. This study provides strong evidence that arbuscular mycorrhizal fungi play an important role in the extent to which plant nutrition of symbiotic N₂-fixing tree species is affected by enriched atmospheric CO₂.     

Effects of carbon dioxide in anther cultures

In anther cultures of Anemone canadensis L., Anemone dichotoma L., Anemone hupehensis Lemoine, Clematis viticella L. and Papaver setigerum DC. a positive relationship between incubation in 2% CO₂ and the production of microspore-derived embryos was observed. In anther cultures of Nicotiana tabacum L., Anemone hupehensis and Clematis viticella a combination of cold treatment (7°C) and incubation in 2% CO₂ increased embryo production. In Anemone canadensis cold treatment increased the number of proembryos, whereas incubation in 2% CO₂ had no effect. In Anemone hupehensis 5% CO₂ increased embryo production by more than 2%. In Anemone dichotoma and Papaver setigerum 2% CO₂ was the more efficient level. CO₂ had no significant effect on pH in the culture medium in anther cultures of Anemone canadensis.     

长期施肥对红壤微生物生物量碳氮和微生物碳源利用的影响

采集湖南省祁阳县红壤长期定位施肥19年的土壤样品,分析长期不同施肥红壤的微生物生物量碳、氮和微生物碳源利用率,以揭示长期施肥对红壤微生物学性状的影响.结果表明：施肥19年后,有机肥单施或与化肥配合施用均显著提高土壤微生物生物量碳、氮和微生物碳源利用率.单施有机肥的土壤微生物生物量碳、氮含量分别为231和81 mg·kg^-1,化肥有机肥配施分别为148和73 mg·kg^-1,均显著高于化肥配施秸秆、不施肥和单施化肥;施用有机肥和化肥配施秸秆的土壤微生物生物量氮占全氮的比例平均为6.0%,显著高于单施化肥和不施肥.Biolog-ECO分析中,平均吸光值(AWCD)的大小为：化肥有机肥配施、单施有机肥>对照>单施化肥、化肥配施秸秆.单施有机肥或与化肥有机肥配施增加了红壤微生物对碳水化合物、羧酸、氨基酸、聚合物、酚类和胺类的碳源利用率;化肥配施有机肥的红壤微生物对聚合物类碳源利用率最高,化肥配施秸秆的红壤微生物对碳水化合物类碳源的利用率最高.表明施用有机肥能显著提高红壤的微生物生物量碳、氮和微生物碳源利用率,提高红壤肥力,保持作物高产.     

环丙沙星对土壤微生物量碳和土壤微生物 群落碳代谢多样性的影响

采用氯仿熏蒸浸提法和Biolog法,分析环丙沙星作用下的土壤微生物量碳和微生物群落碳代谢多样性,以揭示环丙沙星在环境中残留对土壤微生物学性状的影响.结果表明,环丙沙星(wCIP≥0.1 μg/g)对土壤微生物量碳含量影响显著(P＜0.05),土壤中环丙沙星浓度愈高,微生物量碳含量愈低,100μg/g的环丙沙星处理使土壤微生物量碳含量下降58.69％.环丙沙星对土壤微生物群落碳代谢功能影响显著,环丙沙星降低了土壤微生物对碳水化合物、羧酸、氨基酸、聚合物、酚类和胺类的碳源利用率;环丙沙星(wCIP≥0.1 μg/g)显著影响了土壤微生物群落碳源代谢强度和代谢多样性,但不同浓度的环丙沙星对土壤微生物群落碳代谢功能的影响不同,0.1、1、10 μg/g的环丙沙星处理对土壤微生物群落碳代谢功能的影响主要表现在处理前期(用药第7天、21天),这种影响在处理后期(用药第35天)表现不明显,100μg/g的环丙沙星在用药的前期和后期均显著影响土壤微生物群落碳代谢功能,土壤中环丙沙星积累到该浓度可能对土壤微生物群落碳代谢功能产生难以逆转的长期影响.     

Immobilization of D-ribulose-1,5-bisphosphate carboxylase/oxygenase: a step toward carbon dioxide fixation bioprocess

Immobilization of D-ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) from spinach leaves is described. This enzyme enables the fixation of carbon dioxide on a five-carbon sugar D-ribulose-1,5-bisphosphate (RuBP). Two different immobilization methods were employed: dicyclohexylcarbodiimide coupling on nylon membrane matrix and dimethylpimelimidate immobilization on protein A agarose. The reusability of immobilized enzymes, coupling efficiency, and temperature-activity relationship of soluble and immobilized Rubisco are presented. The immobilization imparted greater thermal and storage stability. The thermal deactivation rates of the immobilized enzymes were considerably lower than those of the soluble enzyme.     

根结线虫病土引入秸秆碳源对土壤微生物生物量和原生动物的影响

研究了添加秸秆碳源在连续种植条件下对根结线虫病害严重土壤中微生物生物量和原生动物丰富度的影响. 供试作物为番茄, 设置3个梯度的小麦秸秆添加量\[1N(2.08 g·kg^-1)、2N (4.16 g·kg^-1)和4N(8.32 g·kg^-1)\].结果表明: 添加秸秆碳源对微生物生物量碳、氮和原生动物丰富度具有显著影响,且这种影响呈现为4N>2N>1N>CK.添加秸秆碳源对原生动物群落结构也具有显著影响,各处理鞭毛虫、肉足虫和纤毛虫的平均比例分别为36.0%、59.5%和4.5%.在相同秸秆添加量下,土壤微生物量碳氮、微生物碳氮比和原生动物丰富度随种植年限的延长而提高.     

二氧化碳减排产柴油微藻培养体系研究进展

污水资源化、二氧化碳减排及微藻生物柴油是当前能源与环境领域的前沿课题。以下围绕污水及烟道气资源化培养产油微藻的培养体系,就藻种、营养条件、培养方式、培养环境及微藻生物反应器等影响产油微藻培养的因素研究进展进行了综述。在综述的基础上提出：由于微藻具有特殊营养方式,通过藻种筛选、微藻营养条件和培养环境的优化以及高效光生物反应器和生产工艺等的创新,可利用污水进行产油微藻生产,以获得生物柴油等高附加值产品,实现微藻生物能源、污水资源化处理和CO2减排三者高度耦合的产油微藻生产体系,从而减少微藻培养费用及污水处理费用,因此,该体系具有重要的环境、社会、经济价值和商业化应用前景。     

From open ponds to vertical alveolar panels: the Italian experience in the development of reactors for the mass cultivation of phototrophic microorganisms

The need to develop new concepts in reactor design and the growing interest inSpirulina prompted our group to abandon open ponds in the seventies and to focus interest mainly on closed systems. Two substantially different closed photobioreactors have been developed and are at present under investigation in our Research Centre: the tubular photobioreactor (made of rigid or collapsible tubes) and the recently devised vertical alveolar panel (VAP) made of 1.6-cm-thick Plexiglas alveolar sheets.The technical characteristics of the two systems are described and discussed in relation to the main factors which regulate the growth of oxygenic photosynthetic microorganisms in closed reactors.This paper was presented at the Symposium on Applied Phycology at the Fourth International Phycological Congress, Duke University.     

The air‐lift photobioreactors with flow patterning for high‐density cultures of microalgae and carbon dioxide removal

A photobioreactor containing microalgae is a highly efficient system for converting carbon dioxide (CO₂) into biomass. Using a microalgal photobioreactor as a CO₂ mitigation system is a practical approach to the problem of CO₂ emission from waste gas. In this study, a marine microalga, Chlorella sp. NCTU‐2, was applied to assess biomass production and CO₂ removal. Three types of photobioreactors were designed and used: (i) without inner column (i.e. a bubble column), (ii) with a centric‐tube column and (iii) with a porous centric‐tube column. The specific growth rates (μ) of the batch cultures in the bubble column, the centric‐tube and the porous centric‐tube photobioreactor were 0.180, 0.226 and 0.252 day^?1, respectively. The porous centric‐tube photobioreactor, operated in semicontinuous culture mode with 10% CO₂ aeration, was evaluated. The results show that the maximum biomass productivity was 0.61 g/L when one fourth of the culture broth was recovered every 2 days. The CO₂ removal efficiency was also determined by measuring the influent and effluent loads at different aeration rates and cell densities of Chlorella sp. NCTU‐2. The results show that the CO₂ removal efficiency was related to biomass concentration and aeration rate. The maximum CO₂ removal efficiency of the Chlorella sp. NCTU‐2 culture was 63% when the biomass was maintained at 5.15 g/L concentration and 0.125 vvm aeration (volume gas per volume broth per min; 10% CO₂ in the aeration gas) in the porous centric‐tube photobioreactor.     

Comparison of biooxidation with carbon dioxide assimilation during bacterial growth on ferrous ion or elemental sulfur.

Biomass and oxygen uptake activity profiles of a mixed bioleaching culture were studied and compared at various temperatures. Bacteria were grown on ferrous ion or elemental sulfur in a Micro-Oxymax respirometer apparatus that allowed measurement of both oxygen consumption and carbon dioxide assimilation. Balanced growth was observed between 10 degrees C and 35 degrees C, with an optimum at 30 degrees C, on both energy sources. No significant growth was observed at the lowest temperature used, 5 degrees C, or at the highest temperature used, 40 degrees C. The oxygen to carbon dioxide molar yield was 50:1 when growing on ferrous ion but only 17:1 when growing on elemental sulfur. Upon transfer from a sulfide ore to a new energy source, greater numbers in the inoculum reduced the duration of the lag phase. Lag phase duration was also reduced by proximity to the optimum growth temperature. A longer lag phase decreased the achievable growth rate of the cells exponentially, significantly affecting biooxidation activity.