Photosynthetic performance of a cyanobacterium in a vertical flat-plate photobioreactor for outdoor microalgal production and fixation of CO2

A vertical flat-plate photobioreactor was developed for the outdoor culture of microalgae using sunlight as the light source. The ability for biomass production and CO₂ fixation was evaluated by using a cyanobacterium, Synechocystis aquatilis SI-2. The average areal productivity was 31 g biomass m^–2 d^–1, which corresponded to a CO₂ fixation rate of 51 g CO₂ m^–2 d^–1, sustainable in the northern region of Japan during the winter time (January and February). The relationships between the efficiency of solar energy utilization of the reactor and its effect factors (cell concentration and irradiation) were investigated.     

光生物反应器中螺旋藻培养条件的优化

利用正交实验对搅拌式光生物反应器中钝顶螺旋藻(Spirulina platensis Geitl)的培养条件即搅拌速度、通气量和光照强度进行优化.实验结果表明:当培养温度为30℃时,通过正交实验所获得的最佳培养条件为搅拌转速120 r·min-1,通气量80 L·h-1,光照强度5000lx.在最佳培养条件下,收获时螺旋藻的干重为1.922 g·L-1.根据回归模型得到相应的优化条件为:光照强度5000lx,通气量150L·h-1,搅拌转速111.70r·min-1,收获量(干重)的预测值为2.293 g·L-1.另外,10%的接种量有利于螺旋藻的生长.     

Photosynthetic production of the filamentous cyanobacteriumSpirulina platensis in a cone-shaped helical tubular photobioreactor

The photosynthetic productivity of the filamentous cyanobacteriumSpirulina platensis was investigated in a cone-shaped helical tubular photobioreactor. A laboratory-scale photobioreactor was constructed with a 0.255-m² basal area and a conical shape (0.64 m high × 0.57 m top diameter). The photostage comprised transparent reinforced polyvinyl chloride (PVC) tubing with spirally wound, metal-wire reinforcing in the tubing wall (31 m in length and 1.6 cm internal diameter with 0.25 cm wall thickness; total volume = 6.23 l). The inner surface of the photostage (0.651 m²) was illuminated with compact fluorescent cool white lamps; the photosynthetically active radiation (400–700 nm) energy input into the photobioreactor was 1249 KJ day^–1 (12 h day/12 h night). The operation of an air-lift photobioreactor with CO₂-enriched air (4%) at a flow rate of 0.3 l min^–1 showed a maximum daily photosynthetic efficiency of 6.83% under batch-culture conditions. This corresponded to a production rate of 15.9 g dry biomass m^–2(basal area) day^–1 or 0.51 g dry biomass l medium^–1 day^–1.     

A two-plane tubular photobioreactor for outdoor culture of Spirulina

A photobioreactor in the form of a 245-m-long loop made of plexiglass tubes having an inner diameter of 2.6 cm was designed and constructed for outdoor culture of Spirulina. The loop was arranged in two planes, with 15 8-m-long tubes in each plane. In the upper plane, the tubes were placed in the vacant space between the ones of the lower plane. The culture recycle was performed either with two airlifts, one per plane, or with two peristaltic pumps. The power required for water recycle in the tubular photobioreactor, with a Reynolds number of 4000, was 3.93 x 10(-2) W m(-2). The photobioreactor contained 145 L of culture and covered an overall area of 7.8 m(2). The photobioreactor operation was computer controlled. Viscosity measurements performed on Spirulina cultures having different biomass concentrations showed non-Newtonian behavior displaying decreasing viscosity with an increasing shear rate. The performance of the two-plane photobioreactor was tested under the climatic conditions of central Italy (latitude 43.8 degrees N, longitude 11.3 degrees E). A biomass concentration of 3.5 g L(-1) was found to be adequate for outdoor culture of Spirulina. With a biomass concentration of 6.3 g L(-1), the biomass output rate significantly decreased. The net biomass output rate reached a mean value of 27.8 g m(-2) d(-1) in July; this corresponded to a net photosynthetic efficiency of 6.6% (based on visible irradiance). (c) 1993 John Wiley & Sons, Inc.     

A new approach to ammonium sulphate feeding for fed‐batch Arthrospira (Spirulina) platensis cultivation in tubular photobioreactor

Arthrospira platensis was cultivated in tubular photobioreactor using different photosynthetic photon flux densities (PPFD) and protocols of (NH₄)₂SO₄ fed‐batch supply. Results were evaluated by variance analysis selecting maximum cell concentration (X_m), cell productivity (P_x), nitrogen‐to‐cell conversion factor (Y_X/N) and biomass, protein and lipid contents as responses. At PPFD of 120 and 240 μmol‐photons/m² s, a parabolic profile of (NH₄)₂SO₄ addition aiming at producing biomass with 7% nitrogen content ensured X_m values (14.1 and 12.2 g/L, respectively) comparable to those obtained with NaNO₃. At PPFD of 240 μmol‐photons/m² s, P_x (1.69 g/Ld) was 36% higher, although the photosynthetic efficiency (3.0%) was less than one‐half that at PPFD of 120 μmol‐photons/m² s. Biomass was shown to be constituted by about 35% proteins and 10% lipids, without any dependence on PPFD or kind of nitrogen source. These results highlight the possible use of (NH₄)₂SO₄ as alternative, cheap nitrogen source for A. platensis cultivation in tubular photobioreactors. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Effects of increased atmospheric CO2 and N supply on photosynthesis, growth and cell composition of the cyanobacterium Spirulina platensis (Arthrospira)

The consequences of the addition of CO2 (1%) in cultures of S. platensis are examined in terms of biomass yield, cell composition and external medium composition. CO2 enrichment was tested under nitrogen saturating and nitrogen limiting conditions. Increasing CO2 levels did not cause any change in maximum growth rate while it decreased maximum biomass yield. Protein and pigments were decreased and carbohydrate increased by high CO2, but the capability to store carbohydrates was saturated. C:N ratio remained unchanged while organic carbon released to the external medium was enhanced, suggesting that organic carbon release in S. platensis is an efficient mechanism for the maintenance of the metabolic integrity, balancing the cell C:N ratio in response to environmental CO2 changes. CO2 affected the pigment content: Phycocyanin, chlorophyll and carotenoids were reduced in around 50%, but the photosynthetic parameters were slightly changed. We propose that in S. platensis CO2 could act promoting degradation of pigments synthetised in excess in normal CO2 conditions, that are not necessary for light harvesting. Nitrogen assimilation was significantly not affected by CO2, and it is proposed that the inability to stimulate N assimilation by CO2 enrichment determined the lack of response in maximum growth rate. This revised version was published online in June 2006 with corrections to the Cover Date.     

Production and regeneration of spheroplasts from the cyanobacterium Spirulina platensis

Abstract The development of a micro-method for the production and regeneration of spheroplasts starting from S. platensis trichomes is presented. The influence of the growth stage along with different treatments and conditions on the efficiency of spheroplast formation and regeneration are analyzed.     

钝顶螺旋藻突变株FBL细胞超微结构

利用透射电镜技术观察钝顶螺旋藻出发株和突变株FBL的细胞超微结构。观察结果表明L出发株和突变株均为多细胞丝状体,细胞间横隔膜清晰,细胞壁均由四层结构组成,细胞质膜内陷形成类囊体,类囊体由双层膜堆积而成,膜上附着藻胆体,类囊体与细胞壁呈垂直方向排列,细胞质内包含有充气液泡等细胞器。与出发株相比,突变株细胞壁表面较光滑,四层结构电子密度较深;类囊体膜增多、变发达;羧化体数量增多;横隔膜收缢明显。     

鄂尔多斯高原碱湖的钝顶螺旋藻光合生理研究

鄂尔多斯高原碱湖的钝顶螺旋藻光合色素含量高低排列为藻胆素>叶绿素a>类胡萝卜素;各色素具有特定的吸收光谱,活体吸收光谱体现出了各色素的吸收;各色素的荧光发射主峰波长约长于活体的13￣35nm,相对荧光强度约是活体的11倍。其光合速率的日变化呈单峰曲线,13:00时达到最高;光补偿点为28￣30μmol.m-2.s-1;光饱和点为220￣235μmol.m-2.s-1;光合作用的最适温度为35℃。呼吸速率日变化随温度的升高呈缓慢上升的趋势。     

基于蛋白质组学对螺旋藻砷胁迫响应机制的研究

通过研究螺旋藻(Spirulina sp.)在砷离子胁迫下的蛋白质组变化,从蛋白质表达水平解释螺旋藻对砷离子胁迫的响应机理。螺旋藻经过不同浓度砷离子胁迫7 d后,提取蛋白质进行凝胶电泳,并对差异蛋白进行质谱分析。结果表明螺旋藻在2.0 ppm砷酸盐中暴露10 min光合放氧速率降低27.3%,培养24 h后细胞内的金属硫蛋白、叶绿素、类胡萝卜素及藻胆蛋白相对含量均明显降低。蛋白组学共鉴定出75个差异蛋白,其中26个显著上调,49个呈现下调。这些差异蛋白表明砷离子主要通过破坏螺旋藻光合色素蛋白,干扰电子传递过程,导致能量合成受损,使得依赖光合作用产生能量进行的跨膜运动、蛋白质合成等相关过程受到影响;同时,活性氧清除与防御相关蛋白呈现上调,螺旋藻细胞内抗氧化系统被激活。     

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.     

Spectral kinetic modeling and long‐term behavior assessment of Arthrospira platensis growth in photobioreactor under red (620 nm) light illumination

The ability to cultivate the cyanobacterium Arhtrospira platensis in artificially lightened photobioreactors using high energetic efficiency (quasi‐monochromatic) red LED was investigated. To reach the same maximal productivities as with the polychromatic lightening control conditions (red + blue, P/2e^? = 1.275), the need to work with an optimal range of wavelength around 620 nm was first established on batch and continuous cultures. The long‐term physiological and kinetic behavior was then verified in a continuous photobioreactor illuminated only with red (620 nm) LED, showing that the maximum productivities can be maintained over 30 residence times with only minor changes in the pigment content of the cells corresponding to a well‐known adaptation mechanism of the photosystems, but without any effect on growth and stoichiometry. For both poly and monochromatic incident light inputs, a predictive spectral knowledge model was proposed and validated for the first time, allowing the calculation of the kinetics and stoichiometry observed in any photobioreactor cultivating A. platensis, or other cyanobacteria if the parameters were updated. It is shown that the photon flux (with a specified wavelength) must be used instead of light energy flux as a relevant control variable for the growth. The experimental and theoretical results obtained in this study demonstrate that it is possible to save the energy consumed by the lightening device of photobioreactors using red LED, the spectral range of which is defined according to the action spectrum of photosynthesis. This appears to be crucial information for applications in which the energy must be rationalized, as it is the case for life support systems in closed environments like a permanent spatial base or a submarine. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Isolation and characterization of a metronidazole tolerant mutant of the cyanobacterium Spirulina platensis exhibiting multiple stress tolerance

Mutant cells of Spirulina platensis isolated after chemical mutagenesis (NTG treatment) exhibited approximately three-fold higher tolerance to metronidazole and DCMU (3,4-dichlorophenyl-1, 1-dimethylurea) as compared with wild-type cells. At the same time, mutant cells exhibited a several-fold higher tolerance to supra-high irradiance (38 W/m2) than the wild-type, a further response involving Hill reaction activity in the mutant towards the supra-high irradiance mechanism which enabled the mutant cells to withstand the high light intensities. The metronidazole and DCMU tolerance in the mutant cells could not be obviously attributed to lower rates of growth and photosynthesis as suggested previously. A typical coiling pattern in the mutant cells might result in a reduction of exposed surface area, thereby restricting entry of the above toxins. The mutant strains exhibiting tolerance to multiple stresses are potentially useful for application under field conditions.     

Cultivation of a cyanobacterium in an internally radiating air-lift photobioreactor

This study proposes a new design of the internally radiatingphotobioreactor, which combines the advantages of an air-lift bioreactorand an internally radiating system, and an efficient way of supplying lightenergy into the photobioreactor during cell cultivation. For a modelphotosynthetic microorganism, Synechococcus PCC 6301 wascultivated in an internally radiating air-lift photobioreactor. The lightcondition inside the photobioreactor was characterized by the average lightintensity which was calculated from the light distribution model. Sinceexcessive light energy induced photoinhibition at the early growth stage, thestrategy of lumostatic operation was developed in order to maintain thelight condition at an appropriate level during cell cultivation. Based on thecalculation results of the light distribution model, the average light intensitywas regulated at 30, 60, or 90 mol m^-2 s^-1 byincreasing the number of light radiators. The model-based control ofirradiating level enabled us to harvest a larger amount of cells withoutshowing the photoinhibited growth. Other favorable results included thereduction of cultivation time and lower consumption of irradiating power.     

Construction of a cosmid library of Spirulina platensis as an approach to DNA physical mapping

Abstract A Spirulina platensis gene library has been constructed using cosmid vector pMMB34. The cosmid bank was controlled for its random gene distribution by colony hybridization. Genes were identified using either homologous or heterologous probes of genes involved in photosynthesis (large and small subunit of d -ribulose 1,5-bisphosphate carboxylase, 32 kDa thylakoid protein, α, β subunits of C-phycocyanin) and protein synthesis (elongation factors EF-Tu, EF-G).     

Productivity and photosynthetic efficiency ofSpirulina platensis as affected by light intensity,algal density and rate of mixing in a flat plate photobioreactor

The effect of the rate of mixing on productivity of algal mass in relation to photon flux density and algal concentration was quantitatively evaluated in cultures ofSpirulina platensis grown in a newly designed flat-plate photobioreactor. Special emphasis was placed on elucidating the principles underlying efficient utilization of high photon flux density for maximal productivity of algal-mass. Whereas the rate of mixing exerted little influence on productivity and photosynthetic efficiency in cultures of relatively low algal density, its effect became ever more significant as algal concentration was increased. Maximal mixing-enhanced cell concentrations and productivity of biomass were obtained at the highest light intensity used. At each level of incident light intensity, maximum productivity and photosynthetic efficiency could be achieved only when algal concentration and mixing rates were optimized. The higher the intensity of the light source, the higher became the optimal culture density, highest algal concentrations and productivity of biomass being obtained at the highest light intensity used. The rate of mixing required careful optimization: when too low, maximal productivity resulting from the most efficient utilization of light could not be obtained. Too high a rate of mixing resulted in cell damage and reduced output rate.Author for correspondence     

Photosynthetic phosphorylation by a membrane preparation of the cyanobacterium Spirulina Maxima

A new method for the isolation of photosynthetic membranes from the cyanobacterium Spirulina maxima has been developed. When illuminated, these membranes evolve oxygen in the presence of ferricyanide (Hill reaction) and consume oxygen in the presence of methyl viologen (Mehler reaction). When the membranes are left to stand at 4°C for 30 min, they develop the ability to consume oxygen in the light without an added, artificial electron acceptor. The Hill and Mehler reactions are not affected by the presence of ADP or uncouplers, but are inhibited by triphenyltin chloride. We have detected a cryptic ATPase activity stimulated by trypsin in the 2000×g supernatant fraction of the membrane preparation. In addition, the membrane vesicles contain an ATPase activity which is enhanced by treatment with dithiothreitol in the presence of light. These observations of ATPase led us to try a careful titration of the membrane vesicles with both triphenyltin chloride and N,N′-dicyclohexylcarbodiimide. When the vesicles were sealed with these reagents, we could observe both cyclic and stoichiometric photosynthetic phosphorylation.