Photoinhibition in outdoor Spirulina platensis cultures assessed by polyphasic chlorophyll fluorescence transients

Photoinhibition in outdoor cultures of Spirulina platensis was studied by measuring the polyphasic rise of chlorophyll fluorescence transients, which provide information on the primary photochemistry of PSII. The maximum efficiency of PSII photochemustry (F_v/F_m) declined in response to daily increasing irradiance and recovered as daily irradiance decreased. The greatest inhibition (15%) in F_v/F_m was observed at 12:00 hr which responded to the highest irradiance. The absorption flux, the trapping flux, and the electron transport flux per PSII reaction center increased in response to daily increasing irradiance and decreased as irradiance decreased. The daily change in the concentration of PSII reaction centers followed the same pattern as F_v/F_m. However, no significant changes in the probability of electron transport beyond Q_A (Ψ_o) were observed during the day. The results suggest that the decrease in F_v/F_m induced by photoinhibition in outdoor Spirulina cultures was a result of the inactivation of PSII reaction centers. The results also suggest that the measurement of polyphasic fluorescence transients is a powerful tool to study the mechanism of photoinhibition in outdoor Spirulina cultures and to screen strains for photoinhibition tolerance. This revised version was published online in June 2006 with corrections to the Cover Date.     

倍频Nd：YAG激光对钝顶螺旋藻的诱变效应

利用倍频 Nd:YAG激光 (波长 53 2 nm,功率 50 0 m W,功率密度 1 60 m W/cm2 )诱变钝顶螺旋藻 ,辐照时间为 1 5min、1 0 min、5min通过测定藻丝形态参数、叶绿素 a、β 胡萝卜素、生长速度 ,比较倍频 Nd:YAG激光对钝顶螺旋藻生长的影响。实验结果表明 :与出发株相比 ,经倍频 Nd:YAG激光辐照后 ,藻丝形态发生变化 ,藻丝长、螺旋数、螺旋长变小 ;1 5min,1 0 min辐照组出现螺旋变松驰 ;1 0 min,5min辐照组促进藻的生长和叶绿素 a含量提高 ,使生长速度提高。三个诱变时间剂量都有利于 β 胡萝卡素积累 ,含量增幅最高达 2 2 .3 %。     

螺旋藻连续培养与动力学模型

在内循环气升式光生物反应器中 ,研究了钝顶螺旋藻 (SpirulinaplatensisGeitler)细胞的连续生长及其对碳源底物的利用特性。结果表明 :随着稀释率的增大 ,反应器中碳源浓度和细胞浓度分别呈上升和下降趋势 ,它们之间的关系可用Monod类型的方程很好地加以关联。细胞产率和碳消耗速率与稀释率的关系存在峰值现象 :在本实验条件下 ,最大细胞产率为 0 .36 2g/(L·d) ,最大碳消耗速率为 0 .177g/(L·d) ,此时稀释率为 0 .45 /d ,细胞浓度为OD560 =1.2 82 ,细胞对碳的得率系数为 2 .0 5 0g/g。所提出的连续培养动力学模型与实验数据拟合较好     

Effective transformation of the cyanobacterium Spirulina platensis using electroporation

Although Spirulina (Arthrospira) is expected to be a suitableorganism for producing recombinant proteins, a gene transfer system hasnot yet been established, due to a lack of suitable vectors and because Spirulina appears refractory to common genetic manipulations. As theinitial stages of the development of recombinant DNA methodology, weexamined the effects on transformation efficiency of electroporationconditions such as electric-field strength (2, 4, 6, 8, 10, 12kV cm^-1) and time constant (2.5, 5 ms). At a time constant of2.5 ms, few transformants were observed regardless of the field strength.The longer time constant of 5.0 ms reproducibly yielded transformants atthe middle field strength of 4 - 8 kV cm^-1, but gave high killingand no transformation at the higher field strength of 10 - 12kV cm^-1. Chloramphenicol acetyltransferase (CAT) activities wereincreased only in the transformants from 2–6 kV cm^-1 and 5.0 ms.The density of the transformants was significantly correlated with therelative value of CAT activity (r = 0.89, n = 11, p < 0.01),suggesting that the chloramphenicol resistance was due to CAT activity. Weconcluded that transformation of S. platensis was most effective at apulse duration 5.0 ms with an electric field of 4 kV cm^-1, and thatforeign genes can be expressed in this organism.     

螺旋藻品系Z中不同形态藻丝体的生长速率和光合色素比较

The line-shaped filaments Sp-Z(L) were isolated and cultured from Spirulina platensis Sp-Z. The growth rate of Sp-Z(L) was only 64% as much as that of SP-Z when the light intensity was 4000 Lux. The contentS (×10-3 g / g dry weight) of chlorophylls, carotenoids and phycobilins of Sp-Z(L) and Sp-Z were 20.6, 0.343, 5.00 and 24.1 0.297, 4.46, respectively. Moreover, as to the absorption spectra of the three photopigments of SP-Z(L), red shifts were observed. Therefore, after the spiral Sp-Z breeded or changed…     

Anti‐angiogenic effects of the blue‐green alga Arthrospira platensis on pancreatic cancer

Arthrospira platensis, a blue‐green alga, is a popular nutraceutical substance having potent antioxidant properties with potential anti‐carcinogenic activities. The aim of our study was to assess the possible anti‐angiogenic effects of A platensis in an experimental model of pancreatic cancer. The effects of an A platensis extract were investigated on human pancreatic cancer cells (PA‐TU‐8902) and immortalized endothelial‐like cells (Ea.hy926). PA‐TU‐8902 pancreatic tumours xenografted to athymic mice were also examined. In vitro migration and invasiveness assays were performed on the tested cells. Multiple angiogenic factors and signalling pathways were analysed in the epithelial, endothelial and cancer cells, and tumour tissue. The A platensis extract exerted inhibitory effects on both migration and invasion of pancreatic cancer as well as endothelial‐like cells. Tumours of mice treated with A platensis exhibited much lesser degrees of vascularization as measured by CD31 immunostaining (P = .004). Surprisingly, the VEGF‐A mRNA and protein expressions were up‐regulated in pancreatic cancer cells. A platensis inhibited ERK activation upstream of Raf and suppressed the expression of ERK‐regulated proteins. Treatment of pancreatic cancer with A platensis was associated with suppressive effects on migration and invasiveness with various anti‐angiogenic features, which might account for the anticancer effects of this blue‐green alga.     

Biomass and pigment production for Arthrospira platensis via semi-continuous cultivation in photobioreactors: Temperature effects

This study describes the response of Arthrospira platensis to a variety of temperature conditions as reflected in variations of photosynthetic parameters, pigmentation, and biomass productivity in indoor photobioreactor (PBR) cultivations. These experiments are designed to better understand the impact of temperature, seasonal variations, and acclimation effects on outdoor biomass production. The irradiance level and temperature range (20–39°C) are chosen to enable modeling of semi-continuous operation of large-scale outdoor PBR deployments. Overall, the cultivations are quite stable with some pigment-related instabilities after prolonged high-temperature exposure. Changes in productivity with temperature, as reflected in measured photosynthetic parameters, are immediate and mainly attributable to the temperature dependence of the photosaturation parameter, a secondary factor being variation in pigment content on a longer time scale corresponding to turnover of the culture population. Though pigment changes are not accompanied by significant changes in productivity, prolonged exposure at 35°C and above yields a clear degradation in performance. Productivities in a semi-continuous operation are quantitatively reproduced with a productivity model incorporating photosynthetic parameters measured herein. This study confirms the importance of temperature for biomass and pigment production in Arthrospira cultivations and provides a basis for risk assessments related to temperature mitigation for large-scale outdoor cultivations.     

碳酸盐碱度对钝顶螺旋藻生长的影响

研究了不同碳酸盐碱度浓度条件下,钝顶螺旋藻OD560值、藻液pH值及碳酸盐碱度的变化。结果显示:培养4d后,4mg/L和8mg/L组生长缓慢且呈现下降趋势,OD560值均低于对照组,具有极显著差异(P<0.01),16mg/L和32mg/L组与对照组相比,无显著差异,而64mg/L组具有显著差异(P<0.05)。第6~12d,4mg/L、8mg/L组和16mg/LOD560值均低于对照组,具有极显著差异(P<0.01),32mg/L组无显著差异,而64mg/L组在6~8d,具有显著差异(P<0.05),且在第10~12d,与其它实验组和对照组相比,表现出极显著差异性(P<0.01)。NaHCO3与Na2CO3组成的缓冲体系,其pH值调节功能优于单一使用NaHCO3的对照组。在充气状态下,实验期间各组的碱度始终保持动态平衡。     

CO₂ from alcoholic fermentation for continuous cultivation of Arthrospira (Spirulina) platensis in tubular photobioreactor using urea as nitrogen source

Carbon dioxide released from alcoholic fermentation accounts for 33% of the whole CO(2) involved in the use of ethanol as fuel derived from glucose. As Arthrospira platensis can uptake this greenhouse gas, this study evaluates the use of the CO(2) released from alcoholic fermentation for the production of Arthrospira platensis. For this purpose, this cyanobacterium was cultivated in continuous process using urea as nitrogen source, either using CO(2) from alcoholic fermentation, without any treatment, or using pure CO(2) from cylinder. The experiments were carried out at 120 μmol photons m(-2) s(-1) in tubular photobioreactor at different dilution rates (0.2 ≤ D ≤ 0.8 d(-1) ). Using CO(2) from alcoholic fermentation, maximum steady-state cell concentration (2661 ± 71 mg L(-1) ) was achieved at D = 0.2 d(-1) , whereas higher dilution rate (0.6 d(-1) ) was needed to maximize cell productivity (839 mg L(-1) d(-1) ). This value was 10% lower than the one obtained with pure CO(2) , and there was no significant difference in the biomass protein content. With D = 0.8 d(-1) , it was possible to obtain 56% ± 1.5% and 50% ± 1.2% of protein in the dry biomass, using pure CO(2) and CO(2) from alcoholic fermentation, respectively. These results demonstrate that the use of such cost free CO(2) from alcoholic fermentation as carbon source, associated with low cost nitrogen source, may be a promising way to reduce costs of continuous cultivation of photosynthetic microorganisms, contributing at the same time to mitigate the greenhouse effect.