Growth of Chlorella pyrenoidosa in wastewater from cassava ethanol fermentation

In a cycle tubular photobioreactor, Chlorella pyrenoidosa was cultured in undiluted wastewater from ethanol fermentation using cassava powder as raw material. The results showed that the optimum cultivation conditions were initial pH of 6.0, temperature at 27°C, continuous illumination at 3,000 lux, and cycle speed of 110 ml min⁻¹. Under these optimum conditions, after the logarithmic phase of batch cultivation with wastewater of pH 6.0, the reactor could be continuously operated with natural pH wastewater (3.8) as feed solution. By a dilution ratio of 0.17 day⁻¹, it could be operated stably for over 30 days in continuous cultivation. pH, removal rate of chemical oxygen demand, and biomass (cell dry weight) concentration ranged from 6.22 to 6.47, 72.21 to 76.32% and 3.55 to 3.73 g l⁻¹, respectively. After treatment, the wastewater could be used again in the process of ethanol fermentation.     

利用雨生血球藻(Haematococcus pluvialis)生产天然虾菁素的研究进展

本文综述了当前国内、外利用雨生血球藻生产天然虾菁素的优化条件、雨生血球藻的大规模培养方法以及虾菁素的最佳提取工艺。     

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.     

搅拌式光生物反应器培养海带配子体细胞：不同脉冲补料方式的研究

本文以批次培养为对照,研究了七种脉冲补料方式对搅拌式光生物反应器中培养大型褐藻海带配子体细胞生长和培养液内氮磷营养盐消耗的影响,并首次探讨了脉冲补料方式下不同补料时间点和补料量的影响作用。培养条件设定为50 mg DCW (细胞干重) L-1接种密度、培养液为改良的APSW人工海水、光强60 µE m-2 s-1、光周期16/8 h L/D、通气速率和搅拌速率分别为50 mL min-1和100 rpm。结果表明少量补料利于细胞对氮磷的协同吸收,进而利于生物量扩增。当培养液内氮磷富足或耗尽时补料对于生物量大量生产效果甚微,可能由于氮磷吸收变缓、其储存现象显著,或是其吸收协同性降低。文中当细胞生长至对数中期开始频繁补加少量氮磷营养盐,即维持培养液内氮磷浓度在各自起始浓度的1/3至1/2之间,对生物量生产最有效,生物量增长倍数高达12.270倍。     

Ketocarotenoid production by a mutant of Chlorococcum sp. in an outdoor tubular photobioreactor

A mutant, MA-1, of Chlorococcum sp., grown in batch culture, produced about 54 mg ketocarotenoids/l with 10 mM nitrogen. The accumulation rate of these ketocarotenoids was independent of the nitrogen concentration under sunlight illumination. Fed-batch cultures showed poor growth and the average productivity of ketocarotenoids dropped from 2.6 mg/l day to 1.6 mg/l day in the two consecutive fed-batch runs.     

Pilot-scale open-channel raceways and flat-panel photobioreactors maintain well-mixed conditions under a wide range of mixing energy inputs

Turbulent mixing in pilot-scale cultivation systems influences the productivity of photoautotrophic cultures. We studied turbulent mixing by applying particle image velocimetry and acoustic doppler velocimetry to pilot-scale, flat-panel photobioreactor, and open-channel raceway. Mixing energy inputs were varied from 0.1 to 2.1 W·m⁻³. The experimental results were used to quantify turbulence and to validate computational fluid dynamics models, from which Lagrangian representations of the fluid motion in these reactors were derived. The results of this investigation demonstrated that differences in mixing energy input do not significantly impact the structure of turbulence and the light/dark cycling frequencies experienced by photoautotrophic cells within the reactors. The experimental and computational results of our research demonstrated that well-mixed conditions exist in pilot-scale, flat-panel photobioreactors and open-channel raceways, even for relatively low mixing energy inputs.     

An analytical flat-plate photobioreactor with a spectrally attenuated light source for the incubation of phytoplankton under dynamic light regimes

An inexpensive and simple, analytical microalgal photobioreactor with a highly controllable, dynamic, spectrally attenuated light source is described. Spectral attenuation is achieved through the introduction of a variable thickness of CuSO₄ solution between the photobioreactor and a light source. The level of liquid is precisely determined via a computer-controlled peristaltic pump, which can be programmed to pump at a variety of rates. The resultant light fields consist of a wide range of irradiance intensities with concomitant spectral narrowing, which closely mimics modeled clear water attenuation patterns. Irradiance dynamics associated with virtually any mixing regime can be achieved. The culturing apparatus of the analytical photobioreactor is based on traditional flat-plate, photobioreactor design, but with several modifications: (1) The light path has been reduced to 1 cm to assure a uniform light field is experienced by all phytoplankton at relatively low cell densities; (2) carbon dioxide concentrations are kept constant through a negative feedback mechanism that pulses CO₂ into a constant air stream when culture media pH rises above a set point; (3) temperature is controlled in a similar manner, through the addition of cooling water to a water jacket in response to an increase in culture media temperature. This design is intended for use in photophysiological and bio- physical studies of microalgae under highly controlled culture conditions. It should prove easily adaptable to any number of more complex configurations.     

Progress toward a biomimetic leaf: 4,000 h of hydrogen production by coating‐stabilized nongrowing photosynthetic Rhodopseudomonas palustris

Intact cells are the most stable form of nature's photosynthetic machinery. Coating‐immobilized microbes have the potential to revolutionize the design of photoabsorbers for conversion of sunlight into fuels. Multi‐layer adhesive polymer coatings could spatially combine photoreactive bacteria and algae (complementary biological irradiance spectra) creating high surface area, thin, flexible structures optimized for light trapping, and production of hydrogen (H₂) from water, lignin, pollutants, or waste organics. We report a model coating system which produced 2.08 ± 0.01 mmol H₂ m^?2 h^?1 for 4,000 h with nongrowing Rhodopseudomonas palustris, a purple nonsulfur photosynthetic bacterium. This adhesive, flexible, nanoporous Rps. palustris latex coating produced 8.24 ± 0.03 mol H₂ m^?2 in an argon atmosphere when supplied with acetate and light. A simple low‐pressure hydrogen production and trapping system was tested using a 100 cm² coating. Rps. palustris CGA009 was combined in a bilayer coating with a carotenoid‐less mutant of Rps. palustris (CrtI^?) deficient in peripheral light harvesting (LH2) function. Cryogenic field emission gun scanning electron microscopy (cryo‐FEG‐SEM) and high‐pressure freezing were used to visualize the microstructure of hydrated coatings. A light interaction and reactivity model was evaluated to predict optimal coating thickness for light absorption using the Kubelka‐Munk theory (KMT) of reflectance and absorptance. A two‐flux model predicted light saturation thickness with good agreement to observed H₂ evolution rate. A combined materials and modeling approach could be used for guiding cellular engineering of light trapping and reactivity to enhance overall photosynthetic efficiency per meter square of sunlight incident on photocatalysts. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010