硫与间氯苯腙对海水绿藻Platymonas subcordiformis光照产氢特性的影响

对数生长后期海水绿藻Platymonas subcordiformis具有较高氢酶活性,分别采用培养基中无硫和添加解偶联剂CCCP的方法研究其光照产氢特征.结果表明:无硫连续光照期间,PSⅡ保持较高放氧活性,不能诱导氢酶表达进行光照产氢;厌氧暗诱导32h后,加入5、10、15和20μmol/L的解偶联剂CCCP后光照,PSⅡ光化学活性和光合放氧能力明显被抑制,藻液体系保持厌氧状态,能够持续光照产氢12h以上,光照产氢量分别为21.8、23.0、22.5和16.0μmol/mg Chl;合适浓度的CCCP能够促进绿藻直接光照产氢,但光照产氢量和产氢速率较低.     

解偶联剂CCCP调控海洋绿藻Platymonas subcordiformis 的光照产氢特征

研究了不同浓度解偶联剂CCCP对海水绿藻Platymonas subcordiformis 光照产氢的影响.研究结果显示:厌氧暗诱导后,PSII光化学活性、光合放氧能力和光照产氢能力与CCCP浓度密切相关;藻液中CCCP浓度超过4μmol·L~(-1)时,藻细胞PSII光化学活性被持续抑制,光合放氧能力明显降低,密闭藻液体系能够保持厌氧状态,进行光照产氢12h以上;光照产氢所需电子的90%来自PSII光解水,10%来自内源底物代谢;随着CCCP浓度增加,其对氢酶活性的抑制作用增强.同时,研究了10μmol/L CCCP对不同pH藻液直接光照产氢的影响.     

链霉素对蛋白核小球藻Chlorella pyrenoidosa产氢及其生长的影响

以蛋白核小球藻Chlorella pyrenoidosa为材料,研究不同链霉素浓度对其生长及其产氢过程的影响。结果表明,添加600 mg/L的链霉素对蛋白核小球藻的产氢具有最大促进作用,产氢时间可持续8 d,比对照组延长近6 d,总产氢量为354.54μL/mg,分别是对照组、200 mg/L和1 000 mg/L试验组的18.44,5.85和1.35倍;通过比较不同条件下蛋白核小球藻的光合及生长状况,证实链霉素明显抑制了蛋白核小球藻的光合放氧,对藻细胞产氢后期的生长也有一定抑制作用。     

营养条件对Chlorella vulgaris生长的影响

以Chlorella vulgaris为研究对象,考察了培养基和有机碳源的影响.结果表明:在不同的营养方式中,混养的细胞密度和比生长速率最大,均超过自养和异养之和;改变培养液中的有机碳源种类,C.vulgaris的细胞密度最大分别达到2.92g/L(葡萄糖)、1.62g/L(乙酸钠)和1.05g/L(乙醇),且以葡萄糖为碳源时的比生长速率最大;当葡萄糖浓度从5g/L增加到30g/L时,C.vulgaris的比生长速率由0.0248h-1降低至0.0186h-1,不过在培养晚期,C.vulgaris在10g/L葡萄糖时的细胞密度超过5g/L葡萄糖时的密度;当以10g/L葡萄糖作为C.vulgaris混养的有机碳源时,BG1l培养基的细胞密度和比生长速率最大,分别达到3.41g/L和0.0257h -1,而在Basal培养基中,C.vulgaris 培养液较稳定,藻细胞始终处于悬浮的状态,其细胞密度和比生长速率分别为3.25g/L和0.0204h -1.     

分散性多糖分散绿藻Chroococcidiorella tianjinensis促进其生长和脂类合成的研究北大核心CSCD

微藻是生产生物柴油的重要原料,其培养过程中需要通气和机械搅拌使藻细胞分散,由此提高了培养成本。为降低培养成本,文章采用分散性多糖(DPS)静置培养绿藻。实验结果表明:浓度为0.3 g/L的DPS即能使藻细胞浓度为3 g/L的绿藻培养液均匀分散,使绿藻的生物量和脂类产量比不添加DPS时分别提高49.30%和81.18%;在DPS浓度为0.3 g/L的基础上添加葡萄糖、乙酸钠和碳酸氢钠3种碳源能够进一步促进绿藻的生长,3种碳源的最佳添加浓度分别为30,3.5,1 g/L;在3种碳源的最佳添加浓度下,与不添加碳源添加DPS的培养相比,绿藻的生物量分别提高了122.36%,57.88%和22.55%,脂类含量分别提高了18.00%,23.09%和10.44%,且适合生产优质生物柴油的不饱和脂肪酸C18-0和C18-1的含量也显著提高。     

不同光径对两株土壤绿藻生长及脂类积累的影响

以土壤绿藻1791和1792为试验材料,采用BG-11培养基,分析测定在Φ3×60,Φ6×60 cm两种光径条件下藻的生长和总脂含量。结果表明,两株绿藻在3 cm光径条件下培养获得的最终生物量干重都高于6 cm光径条件,绿藻1791在不同光径条件下的生长从第2天开始出现差异,3 cm试验组的最终干重为4.56 g/L,6cm试验组为3.00 g/L。绿藻1792在培养4 d后藻的生长出现差异,最终3 cm试验组的干重为4.52 g/L,6 cm试验组为3.88 g/L。两株绿藻的叶绿素a含量在培养过程中呈现先上升后下降的趋势。绿藻1791在不同光径条件下的最终总脂含量都比1792的低,最高总脂含量均出现在3 cm光径试验组,在此条件下获得的最大总脂收获量分别为1.63 g/L和1.94 g/L。     

低氮胁迫对两种魏氏藻生长和油脂积累的影响

为了评价低氮胁迫对真眼点藻纲的两株高产油微藻(斧形魏氏藻和点状魏氏藻)的生长和油脂积累的影响,实验设计中将原改良BG-11培养基中的硝酸钠浓度降低为3.6 mmol/L(0.3 g/L)。结果表明:在此浓度下斧形魏氏藻和点状魏氏藻的最高生物量分别为8.21 g/L和9.07 g/L;两者的总脂、中性脂和总脂肪酸含量(占干重)都随着培养时间的延长而不断增加,培养至第18天时分别达到56.4%,64.7%;54%,63.3%;43.5%,45.5%。这两种微藻的主要脂肪酸都含有豆蔻酸、棕榈酸、棕榈油酸、油酸、亚油酸、花生四烯酸和二十碳五烯酸,均适合于生物柴油的生产。它们的总脂、中性脂和总脂肪酸的单位体积产率分别为0.257 g/(L·d),0.326 g/(L·d);0.246 g/(L·d),0.319 g/(L·d)和0.198 g/(L·d),0.229 g/(L·d)。这说明两种微藻在低氮胁迫下都能够获得较高的油脂产率。     

莱茵衣藻和根瘤菌共培养提高产氢条件的优化

将莱茵衣藻(Chlamydomonas reinhardtii)以不同比例与日本慢生大豆根瘤菌(Bradyrhizobium japonicum)混合,在不同光照条件下进行产氢培养,以确定产氢的最优条件和探索产氢提高的机理。结果表明:藻菌共培养的最优产氢条件为25℃、光照200μE/(m~2·s)、生长至饱和期的菌和藻体积比为1∶80,产氢量最大,约为272μmol/(mg Chl),是对照组的17.0倍。藻菌共培养提高产氢量的主要原因是体系中O_2浓度的降低使氢化酶活性提高以及衣藻生物量的增加。     

研究光合生物氢代谢的高灵敏度气相色谱法

本文报道了一种高灵敏度的测氢气相色谱法和几种不同类型光合生物放氢和吸氢活性的初步测定结果。 采用新型碳多孔微球TDX-02作为分离柱固定相,选用ST-04型色谱仪,并用高纯氮作载气,当进样1毫升气体样品时,可检测到0.2ppm(V/V)(相当于1×10~(-11)克分子)的氢气。 测定满江红-鱼腥藻共生体的放氢活性,需在Ar-C_2H_2-CO气相中静止光保温。不同种的满江红在不同气相中放氢活性有差别。兰藻在氩气中振荡光保温时,显示的放氢活性最高。绿藻、红藻和褐藻在厌氧暗适应后,有甲基紫精和连二亚硫酸钠存在下暗保温,能检测到其中氢化酶催化的放氢活性。吸氢活性的检测,需有适量氧和氢的存在。     

聚球藻自相发酵产氢研究

研究了培养基的pH值、盐度和氮源等对聚球藻生长及自相发酵产氢的影响。发现聚球藻在弱碱性时(pH=7.5~8)不能正常生长,当pH值高于8.5时藻才能实现富集,当碱性进一步增强到pH值9.5时藻生长状态最佳。收获藻液置于黑暗厌氧条件下利用自身氢酶进行自相发酵产氢,单位干重的产氢量达到22.25mL/g。聚球藻无法适应高盐度环境,在盐度较低情况下(0.154 mmol/L)才能迅速生长,得到自发酵产氢最大值为25.68 mL/g。加入无机氮源能明显提高聚球藻的生长速率及生物质产量,但对随后产氢效果有抑制作用。     

Truncated chlorophyll antenna size of the photosystems—a practical method to improve microalgal productivity and hydrogen production in mass culture

Unicellular microalgae hold the promise of commercial exploitation in mass culture for hydrogen and biomass production. In any microalgal production system, the achievable photosynthetic productivity and light utilization efficiency of the algae are the single most important factors in the determination of cost. Microalgal mass cultures growing under full sunlight have a low per chlorophyll (Chl) productivity since, at high photon flux densities, the rate of photon absorption by the Chl antenna far exceeds the rate at which photons can be utilized for photosynthesis. Excess photons are dissipated as fluorescence or heat. Up to 80% of absorbed photons could thus be wasted, reducing light conversion efficiencies and cellular productivity to fairly low levels. This shortcoming could possibly be alleviated by the development of microalgal strains with a limited number of Chl molecules in the light-harvesting antenna of their photosystems, i.e., strains that have a truncated Chl antenna size. It is expected that individually, such microalgae will not be able to saturate rates of photosynthesis and, thus, will not be subject to wasteful dissipation of excitation energy. In turn, the productivity of the mass culture will be improved. The method of choice to reach the objective of a “truncated light-harvesting Chl antenna” size (tla) employed DNA insertional and chemical mutagenesis of the unicellular green algae Chlamydomonas reinhardtii and Dunaliella salina, followed by a rigorous screening protocol to identify mutants with a smaller light-harvesting Chl antenna size. Molecular and genetic analyses of isolated tla strains were performed. Biochemical and physiological analyses in terms of photosynthetic productivity and light conversion efficiencies are presented. The results show that a truncated Chl antenna size of PSII is more important than that of PSI in terms of the photosynthetic productivity of a mass culture. A list of genes that confer a “truncated light-harvesting Chl antenna” size to green algae is being compiled for future application in algal hydrogen and biomass production.     

Improvement of hydrogen yield of lba-transgenic Chlamydomonas reinhardtii caused by increasing respiration and impairing photosynthesis

The transgenic alga lba of Chlamydomonas reinhardtii yielded H₂ with 50%–180% higher than the control strain. Further experiments showed that photosynthetic rates and photosynthetic reaction center II's photochemical capacities of the transgenic algae obviously decreased 33.4%–85.9% and 30.0%–51.7%, respectively, compared with those of the control. On the contrary, respiration rates of the transgenic algae significantly increased, with 40.0%–200.0% higher than those of the control. Furthermore, starch contents of the transgenic algae were also improved significantly by 79.1%–592.8% compared with the control. Therefore, the reason of H₂ yield improvement of the transgenic alga lba is not only due to its decrease of photosynthetic capacity and increase of the respiration rate, but also due to the metabolic changes related to starch metabolism, photosynthesis and respiration which is possibly caused by hetero-expression of lba gene in chloroplasts of C. reinhardtii, indicating the potential of utilization of lba gene to improve hydrogen yield of micro-green algae.     

Enhanced hydrogen production through co-cultivation of Chlamydomonas reinhardtii CC-503 and a facultative autotrophic sulfide-oxidizing bacterium under sulfurated conditions

Photoproduction of H₂ using microalgae has been considered as a promising approach for developing sustainable hydrogen energy. The algae C. reinhardtii CC-503 was co-cultured with a facultative autotroph sulfur-oxidizing bacterium Thuomonas intermedia BCRC 17547 to improve H₂ production. The maximum H₂ production of co-culture at sulfur deficiency conditions was 122 μmol/mg Chl with algae/bacteria ratio as 60:1, which was 2.8-fold higher than that of the pure algal culture. Na₂S₂O₃ treatment can result in a maximum H₂ photoproduction rate of 255 μmol/mg Chl, which was 5.9 and 2.1 times higher than those of pure algae culture and co-culture without Na₂S₂O₃. Co-cultivation under sulphate condition can also significantly increase the biomass, respiratory rate, starch content and hydrogenase activity of C. reinhardtii. By supplement of Na₂S₂O₃, persistent (52 days) H₂ production of bacteria/algae co-culture can be achieved. Our results demonstrated that co-culture of C. reinhardtii CC-503 and bacteria BCRC17547 is a cost-effective strategy for improving photobiological H₂ production.     

木屑炭水蒸气催化气化制取合成气研究

以木屑炭为原料,K2CO3作为催化剂,以固定床气化炉为实验设备,进行水蒸气催化气化木屑炭的探究。考察木屑炭水蒸气气化的炭转化率、产氢率、气体组成体积分数和H2/CO比值随K2CO3催化剂质量分数(0~8%)、水蒸气流量(0.15~0.35 g/(min·g))、气化温度(800~950℃)变化的规律。实验结果表明:K2CO3催化剂可显著提升碳转化率及产氢率,K2CO3质量分数为8%时,碳转化率和产氢率分别达到86.3%和125.6 g/kg,同时合成气中CO体积分数显著增加,H2/CO比值降至2.43。增加水蒸气流量,合成气中H2含量显著增大,H2/CO比值随之增大。温度可有效促进炭气化过程,950℃时碳转化率和产氢率分别达到84.3%和127.1 g/kg,但合成气中CO体积分数增大,H2/CO比值降至2.48。实验得到H2/CO比值在2.43~5.16范围的合成气。气化反应温度在900℃、水蒸气0.2 g/(min·g)、K2CO3质量分数3%时,碳转化率可达80.4%,产氢率109.6 g/kg,合成气中(H2+CO)体积分数82.4%,同时H2/CO比值高达3.05。     

Biohydrogen production by novel cyanobacterial strains isolated from rice paddies in Kazakhstan

A limited supply of oil prompts the search for non-traditional energy sources to replace traditional ones. This makes hydrogen gas an appealing alternative source. Photosynthetic organisms capture sunlight very efficiently and convert it into organic molecules. A promising wild strain was isolated for the first time, from the rice paddies of Kazakhstan (Kyzylorda and Almaty regions), which can be considered as one of the most active hydrogen producers compared to the literature. The result showed that among the 13 isolated and collection cyanobacterial strains, Synechocystis sp. S-1 is the most active H₂ producer (2.35 μmol H₂ mg^?1 Chl a h^?1) in the light. In contrast, the wild-type cyanobacterium Anabaena variabilis A-1 had higher productivity, nitrogenase activity, and a stronger capacity to produce hydrogen in the dark (8.67 μmol H₂ mg^?1 Chl a h^?1), which matched the maximum yield obtained in the research. The metabolic modulation performed significantly increased hydrogen production. The highest photohydrogen production rate was observed in cells incubated with 25 μmol HEPES and 50 μmol sodium bicarbonate (NaHCO₃).     

Introducing pyruvate oxidase into the chloroplast of Chlamydomonas reinhardtii increases oxygen consumption and promotes hydrogen production

In an anaerobic environment, the unicellular green algae Chlamydomonas reinhardtii can produce hydrogen (H₂) using hydrogenase. The activity of hydrogenase is inhibited at the presence of molecular oxygen, forming a major barrier for large scale production of hydrogen in autotrophic organisms. In this study, we engineered a novel pathway to consume oxygen and correspondingly promote hydrogen production in Chlamydomonas reinhardtii. The pyruvate oxidase from Escherichia coli and catalase from Synechococcus elongatus PCC 7942 were cloned and integrated into the chloroplast of Chlamydomonas reinhardtii. These two foreign genes are driven by a HSP70A/RBCS2 promoter, a heat shock inducing promoter. After continuous heat shock treatments, the foreign genes showed high expression levels, while the growth rate of transgenic algal cells was slightly inhibited compared to the wild type. Under low light, transgenic algal cells consumed more oxygen than wild type. This resulted in lower oxygen content in sealed culture conditions, especially under low light condition, and dramatically increased hydrogen production. These results demonstrate that pyruvate oxidase expressed in Chlamydomonas reinhardtii increases oxygen consumption and has potential for improving photosynthetic hydrogen production in Chlamydomonas reinhardtii.     

A newly isolated green alga, Tetraspora sp. CU2551, from Thailand with efficient hydrogen production

A novel unicellular hydrogen-producing green alga was isolated from fresh water pond in Pathumthani province, Thailand. Under light microscope, this alga was identified as belonging to the genus Tetraspora. Phylogenetic analysis of 18S rRNA sequence revealed that the green alga, identified as Tetraspora sp. CU2551, is closely related to other unicellular green algal species. Tetraspora sp. CU2551 had the shortest doubling time when grown in Tris-acetate-phosphate (TAP) medium under a light intensity of 48–92 μE/m²/s and a temperature of 36 °C. Hydrogen production increased with increasing pH from 5.75 to 9.30; however, almost no production was observed at a pH of 5.25. Addition of 0.5 mM β-mercaptoethanol to the TAP medium stimulated hydrogen production about two-fold. During the hydrogen production phase, the use of TAP medium lacking both nitrogen and sulfur resulted in about 50% increase in the hydrogen production. This was in contrast to only a small increase in the production when either nitrogen or sulfur was omitted in TAP medium. The stimulation of hydrogen production by 0.5 mM β-mercaptoethanol under nitrogen- and sulfur-deprived conditions occurred only when the cells were grown at a light intensity lower than 5 μE/m²/s with no effects at higher intensities. Maximal calculated hydrogen production, 17.3–61.7 μmol/mg Chl a/h, is a very high production rate compared to other green algae and makes Tetraspora sp. CU2551 an interesting model strain for photobiological hydrogen production.     

Photoautotrophic hydrogen production by nitrogen-deprived Chlamydomonas reinhardtii cultures

In this study we have demonstrated the possibility of phototrophic hydrogen production in C. reinhardtii under N-deprived conditions. When tested under air + CO₂, and Ar + CO₂ N-deprived C. reinhardtii demonstrated decrease in PSII activity mainly due to over reduction of PQ, in addition no ascorbate accumulation was observed in cells. Under air + CO₂ atmosphere cells accumulated excessive amounts of starch. When incubated under Ar + CO₂ atmosphere cells accumulated starch as nitrogen replete cultures and no hydrogen production was observed. Hydrogen production (86 ml H₂ per one l of culture) occurred under Ar + CO₂ atmosphere when particular two-step illumination protocol was implicated. In oxygen producing and early oxygen consuming stage cells were illuminated under light intensity 169 μE m^?2 s^?1. When light was switched to 30 μE m^?2 s^?1, cultures quickly respired all oxygen and transient to anaerobic conditions with subsequent hydrogen production 2 h later. Actual quantum yield of C. reinhardtii cultures was measured in photobioreactor and maximal quantum efficiency of PSII of dark adapted cells together with JIP test were studied.     

Near-infrared absorption carboxylated chlorophyll-a derivatives for biocompatible dye-sensitized hydrogen evolution

Chlorophylls (Chls) are naturally occurring photosensitizers having an excellent visible and near-infrared light absorption property. Herein, we employ three Chl a derivatives as sensitizers in a TiO₂-based photocatalytic system for H₂ evolution with ascorbic acid as the sacrificial reagent under visible light (λ > 400 nm). The H₂-evolution activity of these Chl a derivatives depends on a carboxy group in the C3- and/or C17-substituent(s). The concentration of 1 mg/ml dye/Pt/TiO₂ powder suspended in an aqueous solution with ascorbic acid as the sacrificial reagent gives the highest H₂-evolution rate. The fact that Chl-2 with a carboxy group on the C3 position of the chlorin macrocycle gives the highest H₂-evolution rate of 0.79 μmol h^?1 is ascribed to the lowest charge recombination rate between Chl-2 and TiO₂ among all Chls investigated. This work provides us with important information in synthesizing more favorable molecular structure of Chl derivatives for the highly efficient photocatalytic H₂ evolution from water splitting.     

Renewable algal photo H2 production without S control using acetate enriched fermenter effluents

Renewable energy production using microorganisms is one of the challenging issues for environmental sustainability. Algal hydrogen (H₂) production has often been achieved by sulfur (S) and chloride ion (Cl^?) deprivation in a growth medium; however, it may not be realistic to control S or Cl^? concentrations in natural sources (e.g., wastewater). In this study, two different green algal species, Chlamydomonas reinhardtii and Chlorella sorokiniana were selected and their photosynthetic activities were compared with different acetate/Cl^? ratios both in batch and continuous modes. At 150 of acetate/Cl^? ratio, the H₂ production rates were 0.25–0.33 μmol L^?1 min^?1 for C. sorokiniana and 0.20–0.38 μmol L^?1 min^?1 for C. reinhardtii, respectively. The hydrogenase (HydA) reactivation and photosystem II (PSII) inhibitor test revealed that biohydrogen production by algae is due to photosynthetic activity. It was found that maintaining acetate/Cl^? ratios greater than 60–100 leads to continuous O₂ depletion and thus renewable H₂ production for both algal species. Molecular dynamics (MD) simulations of hydrogen bonding between Y_z and His₁₉₀ in PSII supported O₂ inhibition using acetate. Using fermenter effluents, C. sorokiniana and C. reinhardtii showed a successful continuous H₂ production of ~80 μmol L^?1 and ~95 μmol L^?1, respectively, for 15 days.