Comparison between serum values of pond and intensive raceway cultured channel catfish Ictalurus punctatus (Rafinesque)

Blood serum components in channel catfish ( Ictalurus punctatus ) were compared between raceway (with low dissolved oxygen) and pond populations. Normal limits were defined for the pond populations, for each of 18 variables, as ± two standard deviations. Carbon dioxide, blood urea nitrogen, total protein, uric acid, creatinine, sodium, and total bilirubin were all lower in fish raised in raceways. Carbon dioxide and sodium had the greatest reductions; all reductions were statistically significant.
Alkaline phosphatase, inorganic phosphorus, calcium, cholesterol, and glucose values were higher in raceway fish, but only alkaline phosphatase and glucose were significantly higher.     

Hydrodynamics and mass transfer in a tubular airlift photobioreactor

In photobioreactors, which are usually operated under light limitation,sufficient dissolved inorganic carbon must be provided to avoid carbonlimitation. Efficient mass transfer of CO₂ into the culture mediumisdesirable since undissolved CO₂ is lost by outgassing. Mass transferof O₂ out of the system is also an important consideration, due tothe need to remove photosynthetically-derived O₂ before it reachesinhibitory concentrations. Hydrodynamics (mixing characteristics) are afunctionof reactor geometry and operating conditions (e.g. gas and liquid flow rates),and are a principal determinant of the light regime experienced by the culture.This in turn affects photosynthetic efficiency, productivity, and cellcomposition. This paper describes the mass transfer and hydrodynamics within anear-horizontal tubular photobioreactor. The volume, shape and velocity ofbubbles, gas hold-up, liquid velocity, slip velocity, axial dispersion,Reynoldsnumber, mixing time, and mass transfer coefficients were determined intapwater,seawater, and algal culture medium. Gas hold-up values resembled those ofvertical bubble columns, and the hydraulic regime could be characterized asplug-flow with medium dispersion. The maximum oxygen mass transfer coefficientis approximately 7 h^–1. A regime analysisindicated that there are mass transfer limitations in this type ofphotobioreactor. A methodology is described to determine the mass transfercoefficients for O₂ stripping and CO₂ dissolution whichwould be required to achieve a desired biomass productivity. This procedure canassist in determining design modifications to achieve the desired mass transfercoefficient.     

Productivity of Spirulina in a strongly curved outdoor tubular photobioreactor

 The effect of different flow rates (from 0.18 m∣s to 0.97 m∣s) on the productivity of Spirulina grown outdoors in a strongly curved tubular photobioreactor (CTP) was studied. The results were compared to those obtained with a conventional photobioreactor made with straight tubes to form a loop (STP). The cultures were operated at a biomass concentration of 10 g/l dry weight. The productivity of the culture increased by about 39% and 29% in the CTP and STP respectively when the flow rate of the culture was increased from 0.18 m/s to 0.75 m/s. A further increase of the flow rate did not result in any increase of the productivity in either of the photobioreactors. The better performance of the culture observed in the CTP was attributed to an intermittent illumination pattern resulting from a secondary flow motion generated in the bends. The power required for the induction of the same flow rate inside the two types of photobioreactor changed significantly. At a Reynolds number of 4000, the power absorbed by the CTP was 25% higher than that required for water recycling in the STP and rose by more than 40% at a Reynolds number of 20000. Received: 3 July 1995 / Received revision: 16 October 1995 / Accepted: 24 October 1995     

Productivity of outdoor algal cultures in enclosed tubular photobioreactor

At quasi-steady-state outdoor cyclic fed batch cultures of Chlorella pyrenoidosa, the growth irradiance incidented on the tubular photobioreactor increased about fivefold between 9:00 a.m. and noon. Overheating of the cultures was observed, resulting in decreasing biomass output rate when culture temperature went above 40 degrees C. In cultures with temperature control, the quasi-steady-state output rate of all cultures increased throughout the day and leveled off in the late afternoon in high-density cultures. The daily area output rate was proportional to the density of the cultures. The specific growth rate of the light-limited cultures increased only marginally (20%) in the morning. (c) 1992 John Wiley & Sons, Inc.     

Culture of an autoflocculent microalga in a vertical tubular photobioreactor for phycoerythrin production

Summary A red microalgal, Rhodosorus marinus, was used to produce phycoerythrin. This autoflocculent species, grown in a vertical tubular photoreactor equipped with a gaz-lift system, achieved a growth rate of 0.029 h^-1 with a maximum biomass yield of 2 g.l^-1 dry weight. These values were close to those obtained in batch cultures of other red microalgae cultured as free cell suspensions. Results have shown that these algae could be grown efficiently in natural seawater enriched with nutrients and harvested by decantation followed by filtration.     

Photosynthetic performance of a helical tubular photobioreactor incorporating the cyanobacterium spirulina platensis

The photosynthetic performance of a helical tubular photobioreactor ("Biocoil"), incorporating the filamentous cyanobacterium Spirulina platensis, was investigated. The photobioreactor was constructed in a cylindrical shape (0.9 m high) with a 0.25-m(2)basal area and a photostage comprising 60 m of transparent PVC tubing of 1.6-cm inner diameter (volume = 12.1 L). The inner surface of the cylinder (area = 1.32 m(2)) was illuminated with cool white fluorescent lamps; the energy input of photosynthetically active radiation(PAR, 400 to 700 nm) into the photobioreactor was 2920 kJ per day. An air-lift system ncorporating 4%CO(2) was used to circulate the growth medium in the tubing. The maximum productivity achieved in batch culture was 7.18 g dry biomass per day [0.51 g . d biomass/L . day, or 5.44 g . d biomass/m(2)(inner surface of cylindrical shape)/day] which corresponded to a photosynthetic (PAR) efficiency of 5.45%. The CO(2) was efficiently removed from the gaseous stream; monitoring the CO(2) the outlet and inlet gas streams showed a 70% removal of CO(2) from the inlet gas over an 8-h period with almost maximum growth rate. (c) 1995 John Wiley & Sons, Inc.     

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.     

Vertical tubular photobioreactor for semicontinuous culture of Cyanobium sp

We evaluated the kinetic culture characteristics of the microalgae Cyanobium sp. grown in vertical tubular photobioreactor in semicontinuous mode. Cultivation was carried out in vertical tubular photobioreactor for 2 L, in 57 d, at 30 °C, 3200 Lux, and 12 h light/dark photoperiod. The maximum specific growth rate was found as 0.127 d⁻¹, when the culture had blend concentration of 1.0 g L⁻¹, renewal rate of 50%, and sodium bicarbonate concentration of 1.0 g L⁻¹. The maximum values of productivity (0.071 g L⁻¹ d⁻¹) and number of cycles (10) were observed in blend concentration of 1.0 g L⁻¹, renewal rate of 30%, and bicarbonate concentration of 1.0 g L⁻¹. The results showed the potential of semicontinuous cultivation of Cyanobium sp. in closed tubular bioreactor, combining factors such as blend concentration, renewal rate, and sodium bicarbonate concentration.     

Effect of cell density and irradiance on growth,proximate composition and eicosapentaenoic acid production ofPhaeodactylum tricornutum grown in a tubular photobioreactor

Growth and eicosapentaenoic acid (EPA) productivity of the diatomPhaeodactylum tricornutum grown semicontinuously in a helical tubular photobioreactor were examined under a range of irradiances (approximately 56 to 1712 µmol photons m^-2 s^-1) and cell densities (3 × 10⁶ to 18 × 10⁶ cells mL^-1). Self shading sets the upper limit of operational maximum cell density. Higher irradiance increases this upper limit and also increase the growth rate. Biomass productivity and EPA productivity were enhanced at those cell densities which support the fastest growth rate irrespective of irradiance. The cell protein content increased with increasing irradiance and the carbohydrate and lipid content increased with increasing cell density. EPA productivity was greatest at the highest irradiance. This study shows that biomass productivity and EPA productivity can be maximised by optimising cell density and irradiance, as well as by addition of CO₂.Author for correspondence     

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.     

Seasonal and diurnal changes in the water temperature of a temperate pond (England) and a tropical pond (Kenya)

Seasonal changes in water temperatures, embracing periods of low, rising, high and declining temperatures, were recorded in both a temperate and a tropical pond. In the course of a year, the range between the lowest and highest average weekly temperatures was greater in the temperate pond. The spans between the average minimum and the average maximum weekly water temperatures in the warmest months of the year in the tropical pond were greater than those found at any time of the year in the temperate pond. The average weekly air and water temperatures showed the same pattern of seasonal fluctuations; in the tropical pond the average weekly air temperatures were always less than the average minimum weekly water temperatures, whereas they were below, within or above the spans between the average minimum and average maximum weekly aquatic temperatures, according to the time of year, in the temperate pond.In both ponds, diurnal fluctuations were absent during the cooler months; the amplitudes of the fluctuations in the warmer months varied according to the time of year, and were greater, during the warmest months, in the tropical pond. In both ponds lowest temperatures were recorded sometime between 0200 and 1000 hours and highest between 1200 and 2000 hours.The influence of temperature on the life-cycles of invertebrates in both ponds is discussed briefly.

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Zusammenfassung Jahreszeitlich bedingte Schwankungen in der Wassertemperatur, welche Perioden mit niedriger, ansteigender, hoher und abfallender Temperatur einschlossen, wurden in einem gemäßigten und in einem tropischen Teich festgestellt. Im Laufe eines Jahres war der Unterschied zwischen den tiefsten und höchsten wöchentlichen Durchschnittstemperaturen im gemäßigten Teich größer. Hingegen war der Abstand zwischen Mindest- and Höchsttemperatur des Wassers im Wochendurchschnitt während der warmsten Monate des Jahres im tropischen Teich größer als zu irgendeiner Jahreszeit im gemäßigten Teich. Der Wochendurchschnitt der Luft- und Wassertemperaturen wies das gleiche jahreszeitlich bedingte Schwankungsmuster auf. In dem tropischen Teich war die wöchentliche Durchschnittstemperatur der Luft stets niedriger als die Mindestdurchschnittstemperatur des Wassers in einer Woche. Jedoch lag sie — je nach Jahreszeit — unterhalb, auf gleicher Höhe oder oberhalb der Spannweite der niedrigsten and der höchsten wöchentlichen Dutchschnittstemperaturen des Wassers im gemäßigten Teich.In beiden Teichen traten die taglichen Schwankungen während der kÜhleren Monate nicht auf. Der Umfang der Schwankungen in den wärmeren Monaten variierte je nach Jahreszeit and war in den wärmsten Monaten in dem tropischen Teich größer. In beiden Teichen wurden die tiefsten Temperaturen zwischen 2.00 and 10.00 Uhr and die höchsten zwischen 12.00 and 20.00 Uhr gemessen.

     

Simultaneous nutrients and carbon removal during pretreated swine slurry degradation in a tubular biofilm photobioreactor

The biodegradation potential of an innovative enclosed tubular biofilm photobioreactor inoculated with a Chlorella sorokiniana strain and an acclimated activated sludge consortium was evaluated under continuous illumination and increasing pretreated (centrifuged) swine slurry loading rates. This photobioreactor configuration provided simultaneous and efficient carbon, nitrogen, and phosphorous treatment in a single-stage process at sustained nitrogen and phosphorous removals efficiencies ranging from 94% to 100% and 70–90%, respectively. Maximum total organic carbon (TOC), NH₄ ⁺, and PO₄ ³⁻ removal rates of 80 ± 5 g C m_r ⁻³ day⁻¹, 89 ± 5 g N m_r ⁻³ day⁻¹, and 13 ± 3 g P m_r ⁻³ day⁻¹, respectively, were recorded at the highest swine slurry loadings (TOC of 1,247 ± 62 mg L⁻¹, N–NH₄ ⁺ of 656 ± 37 mg L⁻¹, P–PO₄ ³⁺ of 117 ± 19 mg L⁻¹, and 7 days of hydraulic retention time). The unusual substrates diffusional pathways established within the phototrophic biofilm (photosynthetic O₂ and TOC/NH₄ ⁺ diffusing from opposite sides of the biofilm) allowed both the occurrence of a simultaneous denitrification/nitrification process at the highest swine slurry loading rate and the protection of microalgae from any potential inhibitory effect mediated by the combination of high pH and high NH₃ concentrations. In addition, this biofilm-based photobioreactor supported efficient biomass retention (>92% of the biomass generated during the pretreated swine slurry biodegradation).     

Cultivation of shear stress sensitive and tolerant microalgal species in a tubular photobioreactor equipped with a centrifugal pump

The tolerance to shear stress of Tetraselmis suecica, Isochrysis galbana, Skeletonema costatum, and Chaetoceros muelleri was determined in shear cylinders. The shear tolerance of the microalgae species strongly depends on the strain. I. galbana, S. costatum, and C. muelleri exposed to shear stress between 1.2 and 5.4 Pa resulted in severe cell damage. T. suecica is not sensitive to stresses up to 80 Pa. The possibility to grow these algae in a tubular photobioreactor (PBR) using a centrifugal pump for recirculation of the algae suspension was studied. The shear stresses imposed on the algae in the circulation tubes and at the pressure side of the pump were 0.57 and 1.82 Pa, respectively. The shear stress tolerant T. suecica was successfully cultivated in the PBR. Growth of I. galbana, S. costatum, and C. muelleri in the tubular PBR was not observed, not even at the lowest pumping speed. For the latter shear sensitive strains, the encountered shear stress levels were in the order of magnitude of the determined maximum shear tolerance of the algae. An equation was used to simulate the effect of possible damage of microalgae caused by passages through local high shear zones in centrifugal pumps on the total algae culture in the PBR. This simulation shows that a culture of shear stress sensitive species is bound to collapse after only limited number of passages, confirming the importance of considering shear stress as a process parameter in future design of closed PBRs for microalgal cultivation.     

Use of Chlorella vulgaris for CO(2) mitigation in a photobioreactor

Carbon dioxide (CO₂) is a colorless gas that exists at a concentration of approximately 330 ppm in the atmosphere and is released in great quantities when fossil fuels are burned. The current flux of carbon out of fossil fuels is about 600 times greater than that into fossil fuels. With increased concerns about global warming and greenhouse gas emissions, there have been several approaches proposed for managing the levels of CO₂ emitted into the atmosphere. One of the most understudied methods for CO₂ mitigation is the use of biological processes in engineered systems such as photobioreactors. This research project describes the effectiveness of Chlorella vulgaris, used in a photobioreactor with a very short gas residence time, in sequestering CO₂ from an elevated CO₂ airstream. We evaluated a flow-through photobioreactor's operational parameters, as well as the growth characteristics of the C. vulgaris inoculum when exposed to an airstream with over 1850 ppm CO₂. When using dry weight, chlorophyll, and direct microscopic measurements, it was apparent that the photobioreactor's algal inoculum responded well to the elevated CO₂ levels and there was no build-up of CO₂ or carbonic acid in the photobioreactor. The photobioreactor, with a gas residence time of approximately 2 s, was able to remove up to 74% of the CO₂ in the airstream to ambient levels. This corresponded to a 63.9-g/m³/h bulk removal for the experimental photobioreactor. Consequently, this photobioreactor shows that biological processes may have some promise for treating point source emissions of CO₂ and deserve further study. Received 25 April 2002/ Accepted in revised form 27 July 2002     

Continuous marennin production by agar-entrapped Haslea ostrearia using a tubular photobioreactor with internal illumination

The marine diatom Haslea ostrearia was immobilized in a tubular agar gel layer introduced into a photobioreactor of original design with internal illumination for the continuous synthesis of marennin, a blue-green pigment of biotechnological interest. Marennin was produced for a long-term period (27–43 days) and the volumetric productivity was maximum (18.7 mg day⁻¹ l⁻¹ gel) at the highest dilution rate (0.25 day⁻¹) and lowest agar layer thickness (3 mm). Heterogeneous cell distribution in the agar layer revealed diffusional limitation of light and nutrients. However, the 3 mm gel thickness led to a more homogeneous cell distribution during incubation and to an increase of the whole biomass in the agar gel layer. Received: 22 October 1999 / Received revision: 14 February 2000 / Accepted: 18 February 2000     

Kinetic modeling of the photosynthetic growth of Chlamydomonas reinhardtii in a photobioreactor

The aim of this study was to establish and validate a model for the photosynthetic growth of Chlamydomonas reinhardtii in photobioreactors (PBRs). The proposed model is based on an energetic analysis of the excitation energy transfer in the photosynthesis apparatus (the Z-scheme for photosynthesis). This approach has already been validated in cyanobacteria (Arthorspira platensis) and is extended here to predict the volumetric biomass productivity for the microalga C. reinhardtii in autotrophic conditions, taking into consideration the two metabolic processes taking place in this eukaryotic microorganism, namely photosynthesis and respiration. The kinetic growth model obtained was then coupled to a radiative transfer model (the two-flux model) to determine the local kinetics, and thereby the volumetric biomass productivity, in a torus PBR. The model was found to predict PBR performances accurately for a broad set of operating conditions, including both light-limited and kinetic growth regimes, with a variance of less than 10% between experimental results and simulations.     

Neochloris oleoabundans oil production in an outdoor tubular photobioreactor at pilot scale

Journal of Applied Phycology - Oil production was tested with Neochloris oleoabundans in a 6 m3, horizontal soft sleeve tubular reactor from 22 October to 7 November in Matalascañas,...