A new photobioreactor for continuous microalgal production in hatcheries based on external-loop airlift and swirling flow

This study deals with the scale of a new photobioreactor for continuous microalgal production in hatcheries. The combination of the state-of-art with the constraints inherent to hatcheries has turned the design into a closed, artificially illuminated and external-loop airlift configuration based on a succession of elementary modules, each one being composed of two transparent vertical interconnected columns. The liquid circulation is ensured pneumatically (air injections) with respect to a swirling motion (tangential inlets). A single module of the whole photobioreactor was built-up to investigate how parameters, such as air sparger type, gas flow rate, tangential inlet, column radius and height can influence radiative transfer, hydrodynamics, mass transfer and biological performances. The volumetric productivities were predicted by modeling radiative transfer and growth of Isochrysis affinis galbana (clone Tahiti). The hydrodynamics of the liquid phase was modeled in terms of global flow behavior (circulation and mixing times, Péclet number) and of swirling motion decay along the column (Particle Image Velocimetry). The aeration performances were determined by overall volumetric mass transfer measurements. Continuous cultures of Isochrysis affinis galbana (clone Tahiti) were run in two geometrical configurations, generating either an axial or a swirling flow. Lastly, the definitive options of design are presented as well as a 120 Liter prototype, currently implemented in a French mollusk hatchery and commercialized

Effects of Sodium Bicarbonate and photoperiod on Cell Growth and morphology of Isochrysis galbana

Microalgae play a vital role in many aquaculture feed application processes. Maintaining a microalgae production facility has been estimated to account for an average of 30 % and up to 60 % of the total budget of aquaculture hatcheries, despite several research programs and global efforts to reduce production costs of algal biomass. The use of bicarbonate as carbon inorganic to produce microalgae biomass for bivalve hatcheries was proposed as an alternative to reduce this cost. The focus of this investigation is characterization of the interaction of bicarbonate-based microalgae cultivation and photoperiod on the growth rate and production of brown microalgae Isochrysis galbana. The salt was provided to the cultures at the final concentration from 0.5 to 2.5 g L-1. Concerning photoperiod, two cycles of light:dark (6:18 and 12:12) were studied under light intensity at 160 µmol m-2 s-1. The growth rate of Isochrysis galbana showed values significantly higher in the culture supplemented with 0.5 and 1 g L-1 of NaHCO3 respectively under cycles 6L:18D and 12L:12D. Bicarbonate administration leads to a significant increase in cellular size at the stationary phase, probably related to starch or lipid accumulation. This study proved that the addition of bicarbonate is a viable strategy to enhance the production of microalgae and reduce production costs

Isochrysis affinis galbana ve Phaeodactylum tricornutum Kültürlerinde Kuru Madde Tahminlerinin Karşılaştırılması

Isochrysis affinis galbana tek hücreli denizel bir mikroalg türü olup yüksek miktarda uzun zincirli doymamış yağ asitleri (PUFA) içermesinden dolayı akuakültürde özellikle bivalvia larvalarının beslenmesinde canlı yem kaynağı olarak kullanılmaktadır. Phaeodactylum tricornutum ise oval ve fusiform hücre şekilleri olan tek hücreli pennat bir diyatom türüdür. Phaeodactylum tricornutum %30-45 arasında uzun zincirli doymamış yağ asitlerini (PUFA) içermekte ve bu oranın da %20-40’ını eikosapentaenoik asit (EPA) oluşturmaktadır. Esansiyel yağ asitlerinden eikosapentaenoik asit'in önemli potansiyel kaynağı olarak düşünülen mikroalgler insan gıdası olarak ve akuakültürde hayvan beslenmesinde kullanılmaktadır. Çalışmada, Isochrysis affinis galbana ve Phaeodactylum tricornutum kültürlerine ait kuru madde miktarlarının çoklu regresyon analizi yöntemi kullanılarak tahmin edilmesi amaçlanmıştır. Türler, F/2 besi ortamında %20 aşılama oranı ile kontrol grubu ve %50 oranında azotun eksiltildiği besi ortamı kullanılarak, laboratuvar ortamında kültüre alınmıştır. Deneme süresince optik yoğunluk, kuru madde ve klorofil a günlük olarak ölçülmüştür. Türlere ait kontrol grubu ve %50 oranında azotun eksiltildiği gruplarda optik yoğunluk ve klorofil a kullanılarak matematiksel bir model oluşturulmuştur. Bu modellerin önem testleri yapılıp, R2 ve HKO bulunmuştur

The Effect of Nitrogen Deficiency on the Growth and Lipid Content of Isochrysis affinis galbana in Two Photobioreactor Systems (PBR): Tubular and Flat Panel

Energy is becoming one of the most expensive production inputs nowadays. Energy reserves are starting to run out and their polluting nature has become undeniable. Therefore, there is an urgent necessity for renewable energies. One of these energy sources is algae, which are seen as promising for biofuel production. Algae can be cultured in non-agricultural land, high photosynthetic activity, harvested throughout the year high biomass production. High lipid from algae is possible by reducing some elements of growth conditions from the nutrient medium. In this study, Isochrysis affinis galbana species were cultured in two reactors; flat panel photobioreactors with different light paths (1, 3, 5, 7 and 10 cm) and tubular photobioreactors, with 50% nitrogen reduction and 20% inoculation densities. Biomass, lipid and protein ratios were determined. The highest lipid content of 33.13% was obtained from I. aff. galbana with 12.11% protein in flat panel photobioreactors with 50% nitrogen reduction and 10 cm light path, and a 0.991 g L-1 biomass rate was obtained. The highest optical density was found in the 10 cm light path flat panel photobioreactor with a 50% nitrogen reduction

Biomass production and biochemical composition in mass cultures of the marine microalga Isochrysis galbana Parke at varying nutrient concentrations

Mass cultures of Isochrysis galbana were carried out with four nutrient concentrations ranging from 2 to 16 mM of NaNO3 and salinity 35‰. An air flow of 15 l/min maintained a CO2 transference rate sufficient to keep the pH below 8.4. Using these conditions, equations were calculated by a multiple non-linear least squares regression of order four, enabling predictions to be made of growth kinetics and chemical composition. Maximum cellular density of 65.5 × 106 cells/ml was obtained with 4 mM NaNO3. Cellular volume was constant in the different nutrient concentrations. Protein content reached a maximum value of 374 μg/ml at 4 mM of NaNO3, and this concentration also presented the maximum efficiency of transformation from nitrate to protein, i.e. 114%. As a result, lowest costs for harvesting are obtained at a nutrient concentration of 4 mM NaNO3. Efficiencies decreased to 15% as nutrient concentration increased. Maximum values of chlorophyll a (21.9 μg/ml) and carbohydrates (213 μg/ml) were also obtained with 4 mM NaNO3. In the logarithmic phase, the contents of protein, chlorophyll a, carbohydrates, RNA and DNA per cell were constant. Chlorophyll a reached values between 0.15 and 0.33 pg/cell in the stationary phase. Carbohydrate levels reached the maximum value of 3.16 pg/cell with 4 mM NaNO3 in the stationary phase. The levels of RNA/cell and DNA/cell were constant in all the nutrient concentrations tested and in both growth phases, and ranged from 1.15 to 1.71 pg/cell for RNA and from 0.006 to 0.014 pg/cell for DNA. Growth in mass cultures is closely coupled to changes in nutrient concentrations and variations occur in protein, chlorophyll a and carbohydrate contents, showing differences of 177%, 220% and 136%, respectively, in the stationary phase. This biochemical variability, mainly in protein content, must have a marked effect on the nutritive value of this microalga as a feed in mariculture

Potencial de absorção de carbono por espécies de microalgas usadas na aqüicultura: primeiros passos para o desenvolvimento de um “mecanismo de desenvolvimento limpo”

The aim of this work was to determine the rate of CO2 uptake of the microalgae species Nannochloropsis oculata, Chaetoceros affinis, Chaetoceros muelleri, Phaeodactylum tricornutum, Skeletonema costatum, Thalassiosira weissflogii, Thalassiosira pseudonana, Tetraselmis chuii, Tetraselmis tetrathele and Isochrysis galbana, used in aquaculture. Measurements of primary production (14C method; dissolved, particulate and total production) were accomplished in cultures growing in logarithmic phase, under different light intensities and without any nutrient restriction. T. weissflogii and N. oculata presented the largest carbon uptake rates, being indicated for further scaling experiments in order to develop a “Clean Development Mechanism” to the absortion of atmospheric carbon dioxide.O objetivo deste trabalho foi o de determinar a taxa de absorção de CO2 das espécies de microalgas, Nannochloropsis oculata, Chaetoceros affinis, Chaetoceros muelleri, Phaeodactylum tricornutum, Skeletonema costatum, Thalassiosira weissflogii, Thalassiosira pseudonana, Tetraselmis chuii, Tetraselmis tetrathele e Isochrysis galbana, normalmente utilizadas na aqüicultura. Medidas de produção primária (método do 14C; produção dissolvida, particulada e total) foram realizadas em cultivos que estavam em fase logarítmica, sob diferentes intensidades luminosas e sem restrições nutritivas. T. weissflogii e N. oculata apresentaram os maiores valores de absorção de carbono, sendo indicadas para a realização de experimentos em grande escala, visando o desenvolvimento de um “Mecanismo de Desenvolvimento Limpo” para absorção de dióxido de carbono atmosférico

Characterization of the phytoplankton size composition and light absorption coefficient in the temperate coastal waters of Sagami Bay

Phytoplankton constitute the base of the aquatic food web and are the primary driver of biogeochemical processes such as the e port of carbon to the deep ocean. Knowledge of the distributions, compositions, and biomass of the phytoplankton community are essential to under stand biogeochemical cycles. Phytoplankton can be enumerated by microscopy, but this requires e tensive time for sample preparation and counting, especially if statistically valid counts of the less abundant phytoplankton classes are required. Further, smaller picoplankton can be difficult to identify since they lack ta onomically e ternal morphological features. Thus, the accessory pigment-based model has been used to estimate phytoplankton communities based on their size classes: micro- (M; > 20 µm), nano- (N; 2-20 µm) and pico-phytoplankton (P; < 2 µm). Light absorption by phytoplankton has a direct influence on the optical properties of seawater, and there is a growing effort to develop approaches to identify the spatial and temporal variability of the phytoplankton community from satellites. However, estimating the phytoplankton com munity in optically comple coastal waters from satellites is still a challenging problem because phytoplankton are only one of multiple optically significant constituents of seawater. Also, there are limitations of wavelength that satellites can measure, and overlapping signature pigment of each phytoplankton community. In order to improve the estimation of phytoplankton communi ties, it is necessary to understand the light absorption coefficient of phytoplankton, aph (,,) asso ciated with the varying community structure. The objective of this study was to characterize the variability of phytoplankton size classes and their light absorption coefficients in the temperate coastal waters of Sagami Bay. The specific objectives were (1) to classify phytoplankton com munities based on cell size, (2) to investigate co-variability of aph (,,) spectra according to the classification. The present study conducted in situ observations from April 2016 to September 2022 at Station M (St. M: 35° 09’ 45” N, 139° 10’00” E) in the temporal coastal waters of Sagami Bay, Japan. Water samples for pigments and light absorption properties of phytoplankton were collected from surface water with a bucket, and measured by high-performance liquid chroma tography and spectrophotometry, respectively. Phytoplankton size class composition was esti mated based on pigment concentrations. The results showed that the three groups (Group M, N, P) generated according to the phytoplankton size composition were significantly different (R = 0.646, p < 0.001). Also, the most dominant group throughout the study period was microplank ton (n = 110). The aph (,,) spectra showed peaks around 438 nm and 465 nm in the blue band and 674 nm in the red band. Using three wavelengths peaks, although the aph (,,) of group M was sig nificantly higher than that of group N, Group P was not significantly different from other groups. This study suggests that the aph (,,) spectrum in the temperate coastal waters of Sagami Bay is significantly co-varying with the variability of phytoplankton size composition. The results sug gest that analyzing the difference in aph (,,) spectra ratios and performing derivative analysis, coupled with analysis of phytoplankton size distribution and pigment composition should im prove our ability to characterize phytoplankton spatio-temporal distribution from space.departmental bulletin pape

LEDs to Replace Fluorescent Tubes for Growth of Cultured Algae

Fluorescent bulbs are widely used for algal culture stocks and production in aquaculture operations. Metal halide lamps are also used for production tanks with significant electricity demand and heat production. LED technology promises lower operational costs with less energy waste as heat for equivalent light energy production. Re-tooling algal production facilities with new LED fixtures incurs significant expense that must be recaptured in savings over time. The initial cost, added to concerns over the unknown response of algae to LED light sources may both be factors inhibiting incorporation of this new technology. LED replacement tubes are available to retrofit fluorescent tube fixtures and may offset some conversion costs to replacing light sources. Concerns about the ability of LEDs to provide adequate algae production for hatchery operations led us to run side by side comparison of growth dynamics for four commonly used algae strains using fluorescent light and LED replacement tubes. We also implemented a tunable red and blue LED unit for mass algae production in tanks

Culture of the Calanoid Copepod, Acartia erythraea and Cyclopoid Copepod, Oithona brevicornis with various Microalgal diets

Two experiments were conducted to develop Acartia erythraea and Oithona brevicornis cultures: The performance of five microalgal diets to produce nauplii, copepodites and adults of A. erythraea; and the performance of the same diets to produce nauplii, copepodites and adults of O. brevicornis. The five different microalgal diets were Isochrysis galbana (IG), Chaetoceros affinis (CA), Chlorella marina (CM), Nannochloropsis oculata (NO) and mixed algae (mixture of IG, CA, CM and NO at an equal abundance to provide the exact cell density). The results indicated that the abundance of both A. erythraea and O. brevicornis was higher in tanks supplied with IG and mixed algae than the tanks supplied with CA, CM and NO. IG and mixed algal diets were statistically similar on the mean abundance for both A. erythraea and O. brevicornis. The maximum production of A. erythraea nauplii was observed on day 12 of culture period and the nauplii production decreased from day 13 onwards. The mean abundance of A. erythraea copepodites and adults increased along with time up to the end of the culture period. In the case of O. brevicornis nauplii, the maximum abundance was observed on day 9 day of culture period and the nauplii production decreased from day 10 onwards. The mean abundance of O. brevicornis copepodites and adults increased gradually from the beginning to the end of the culture period. Under the experimental conditions of this study, both IG and mixed algal diets can be recommended for the best growth performance of A. erythraea and O. brevicornis