Evaluation of the interactions between the marine bacterium Pseudomonas fluorescens and the microalga Isochrysis galbana in simulated ballast tank environment.

To evaluate the impacts of the interaction between bacteria and microalgae has been the object of study by many research groups around the world. However, little is known about the interference that pigments produced by bacteria, such as the pyoverdine siderophore, can cause to microalgae like Isochrysis galbana. Pyoverdine is a fluorochrome produced by certain Pseudomonas strains, such as P. fluorescens, which plays a role in capturing and transporting iron ions from the environment to the cell. Unlike the oceans where Fe concentrations are extremely low (< 10-15 µM), in a ballast tank it is expected that there is a great supply of iron to the cells and that the absence of light is the main limiting factor until the water is discarded. Interestingly, under certain conditions, bacteria such as P. fluorescens absorb most of the water soluble iron ions and prevent the growth of phytoplankton even if there is sufficient light. Changes in the patterns of light distribution in aquatic environments may affect the physiological characteristics of certain microalgae. This study aimed to evaluate the impacts of the presence of P. fluorescens on the survival and growth of I. galbana inside the tank. For the study, an experiment was carried out to study the interaction between P. fluorescens and I. galbana under simulated conditions of a vessel in the presence/absence of Pseudomonas and light. The results showed that the presence of the bacteria is not the main limiting factor for microalga growth. The effect of the light factor was determinant on the reproduction rate. It is believed that pyoverdine produced by P. fluorescens affected I. galbana stock either by increasing mortality or decreasing growth rate as revealed by laboratory experiments. However, it was not possible to check if the pigment concentration was affected by the growth of microalgae.

Influence of High Light Intensity and Nitrate Deprivation on Growth and Biochemical Composition of the Marine Microalgae Isochrysis galbana

Abstract Isochrysis galbana is a brown microalgae widely used as a feed for marine organism in aquaculture. The aim of present study is to investigate the growth, biochemical composition, fatty acid profile, photosynthetic parameters and antioxidant activity (radical scavenging activity) of Isochrysis galbana cells cultivated under different levels (sub-optimum; 50 ± 1.5,optimum; 125 ± 2.5 and supra-optimum; 325 ± 3.5 µmol photons m-2 s -1) of photosynthetic active radiation (PAR), and subsequently treated with different concentration of nitrate deprivation (8mM, 2mM and 0.5mM). The experiment was carried out under controlled conditions utilizing a factorial design 3x3 (light intensity and nitrate concentration). The result depicts that PAR positively influences the growth of Isochrysis galbana which is maximum under supra-optimum PAR. Nitrate deprivation (2mM & 0.5mM) induced decline in growth in terms of dry weight is observed as 60.1% & 61.9% in suboptimum and 26.5% and 34.9% in supra-optimum respectively over the values recorded in their respective controls. Supra-optimum PAR decreased primary photosynthetic pigment Chl a and Chl c by 15.7% and 8.5%, whereas carotenoid content increased by 45.9% in supra-optimum PAR which displays potential interest as antioxidant agent in addition to total phenolic content and radical scavenging activity. The results suggest that combined stress of high light and nitrogen deprivation shifts the metabolic physiology from protein synthesis to energy reserve (carbohydrate and lipid) and accumulation of saturated fatty acid on expense of unsaturated fatty acid except docosahexaenoic acid. These valuable compounds exhibit potential applications in mariculture, nutraceutical and biofuel industry.

Methane production from marine microalgae Isochrysis galbana.

Methane production from marine microalgae Isochrysis galbana was assessed before and after mechanical and chemical pretreatments. Mechanical pretreatment resulted in a 61.7% increase in soluble Chemical Oxygen Demand. Different hydrolysis conditions were evaluated by varying temperature - T, sulfuric acid concentration - AC and biomass suspension concentration (measured as particulate COD - CODp) using an experimental design. The most significant interaction occurred between AC and T and the hydrolysis condition that showed the best result in the anaerobic digestion step was the condition at 40°C with addition of 0.2% (v/v) acid for 16h (9.27LCH4/kgVS). The low methane yields were attributed to inhibitory sodium concentrations for anaerobic digestion. Eliminating inhibitory sodium in the anaerobic digestion by biomass prewashing, there was a 71.5% increase in methane yield for biomass after acid hydrolysis, demonstrating the need for pretreatment and reduction in sodium concentration in the anaerobic digestion.

Effects of CO2 enrichment and nutrients supply intermittency on batch cultures of Isochrysis galbana.

Aiming at enhanced performance to increase economic feasibility of microalgae based processes, Isochrysis galbana was grown in three modes of cultivation: batch, intermittent fed batch and semi-continuous. The batch mode was conducted under two regimes of aeration: conventional aeration and CO2 enriched aeration (5% v/v in air). Increased biomass productivity without significant impact on lipid accumulation was observed for CO2 enriched aeration relatively to cultivation aerated with air only. The intermittent fed batch cultivation policy was proven to be useful for lipid accumulation, increasing the lipid content by 19.8%. However, the semi-continuous mode resulted in higher productivity due to increased biomass concentration; the biomass productivity reached 0.51 g/(Ld). Fluorescence measurements were performed; the calculated low electron transport rate showed the need to increase the irradiance. The results showed that I. galbana can be grown in semi-continuous condition at high levels of biomass productivity.

Maturation of native oyster Crassostrea gasar at different diets in the laboratory / Maturação da ostra nativa Crassostrea gasar submetida a diferentes dietas em laboratório

This study evaluated the influence of different microalgae diets on gonadal tissue maturation in the native oyster Crassostrea gasar in the laboratory, between March and May 2010, totalizing 60 days. Ninety-six oysters, collected from an experimental farm located on Florianópolis/SC, were transferred to the laboratory and maintained in three different diet treatments: Isochrysis galbana, Chaetoceros müelleri and a mix diet of both species in a 1:1 ratio. The oysters were conditioned in 3 L experimental units at a water flow rate of 300 mL min-1 and constant aeration. Food was provided in a continuous flow system, at a density of 16 x 104 cells mL-1. The mean water temperature and salinity during the experimental period were 24.36 ± 1.23 ºC and 29.4 ± 3.08, respectively. Fortnightly, six oysters randomly sampled from each treatment were examined for histological analysis. The condition index was analyzed at the beginning and the end of the experiment. The initial mean height and weight of the oysters were 68.25 ± 6.73 mm and 60.89 ± 14.19 g, respectively, and the final mean height and weight were 69.20 ± 5.97 mm and 70.04 ± 17.42 g, respectively. The sex ratio for the treatments was 1.2 males for each female and 19.5% of the oysters were considered indeterminate. The condition index was not affected by treatments and there was no improvement on the gonadal tissue maturation of t

Este estudo avaliou a influência de diferentes dietas microalgais sobre a maturação do tecido gonádico da ostra nativa Crassostrea gasar em laboratório, entre março e maio de 2010, totalizando 60 dias. Noventa e seis ostras, coletadas em cultivo experimental localizado em Florianópolis/SC, foram transferidas para o laboratório e submetidas a três tratamentos de alimentação: Isochrysis galbana, Chaetoceros müelleri e uma dieta mista das duas espécies na proporção de 1:1. As ostras foram acondicionadas em unidades experimentais de 3 L com vazão de 300 mL min-1 de água e aeração constante. A alimentação foi fornecida em sistema de fluxo contínuo, na densidade de 16 x 104 células mL-1. A temperatura e salinidade média da água durante o período experimental foram 24,36 ± 1,23 ºC e 29,4 ± 3,08, respectivamente. Quinzenalmente, foram realizadas análises histológicas de seis indivíduos amostrados aleatoriamente de cada tratamento. O índice de condição foi calculado no início e no fim do experimento. A altura e peso inicial das ostras foram 68,25 ± 6,73 mm e 60,89 ± 14,19 g, respectivamente, e a altura e peso final foram 69,20 ± 5,97 mm e 70,04 ± 17,42 g, respectivamente. A proporção sexual dos tratamentos foi 1,2 machos para cada fêmea e 19,5% das ostras foram consideradas indeterminadas. O índice de condição não foi afetado pelos tratamentos e não houve melhora na maturação do tecido

Maturação da ostra nativa Crassostrea gasar submetida a diferentes dietas em laboratório / Maturation of native oyster Crassostrea gasar at different diets in the laboratory*

This study evaluated the influence of different microalgae diets on gonadal tissue maturation in the native oyster Crassostrea gasar in the laboratory, between MarchandMay 2010, totalizing60 days. Ninety-six oysters, collected from anexperimental farm located on Florianópolis/SC,were transferred to the laboratory and maintained in three different diet treatments:Isochrysisgalbana, Chaetocerosmüelleriand a mix diet of both speciesin a 1:1 ratio. The oysters were conditioned in 3Lexperimental units at a water flow rate of 300 mLmin-1and constant aeration. Food was providedin a continuous flow system, at a density of16x104cells mL-1. The mean water temperature andsalinity during the experimental period were 24.36 ± 1.23ºC and 29.4 ± 3.08, respectively. Fortnightly,six oysters randomly sampled from each treatment were examined for histological analysis. The condition index was analyzedat the beginning and the end of the experiment. The initial mean height and weight of the oysters were 68.25 ± 6.73 mm and 60.89 ± 14.19g, respectively, and the final mean height and weight were 69.20 ± 5.97 mm and 70.04 ± 17.42 g, respectively.The sex ratio for the treatments was 1.2 males for each female and 19.5% of the oysters were considered indeterminate. The condition index was not affected by treatmentsandthere was no improvement on the gonadal tissue maturation of the native oyster C. gasarsubjected to different microalgae diets during the conditioning period.(AU)

Este estudo avaliou a influência de diferentes dietas microalgais sobre a maturação do tecido gonádico da ostra nativa Crassostrea gasarem laboratório, entre março e maio de 2010, totalizando60 dias. Noventa e seis ostras, coletadas em cultivo experimental localizado em Florianópolis/SC, foram transferidas para o laboratório e submetidas a três tratamentos de alimentação: Isochrysisgalbana, Chaetocerosmüellerie uma die Este estudo avaliou a influência de diferentes dietas microalgais sobre a maturação do tecido gonádico da ostra nativa Crassostrea gasarem laboratório, entre março e maio de 2010, totalizando60 dias. Noventa e seis ostras, coletadas em cultivo experimental localizado em Florianópolis/SC, foram transferidas para o laboratório e submetidas a três tratamentos de alimentação: Isochrysisgalbana, Chaetocerosmüellerie uma dieta mista das duas espécies na proporção de 1:1. As ostras foram acondicionadas em unidades experimentais de 3 L com vazão de 300 mLmin-1de água e aeração constante. A alimentação foi fornecida em sistema de fluxo contínuo, na densidade de 16x104célulasmL-1. A temperatura e salinidade média da água durante o período experimental foram 24,36 ± 1,23ºC e 29,4 ± 3,08, respectivamente. Quinzenalmente, foram realizadas análises histológicas de seis indivíduos amostrados aleatoriamente de cada tratamento. O índice de condição foi calculado no início e no fim do experimento. A altura e peso inicial das ostras foram68,25 ± 6,73 mm e 60,89 ± 14,19g, respectivamente, e a altura e peso final foram 69,20 ± 5,97 mm e 70,04 ± 17,42 g, respectivamente. A proporção sexual dos tratamentos foi1,2 machos para cada fêmea e 19,5% das ostras foram consideradas indeterminadas. O índice de condição não foi afetado pelos tratamentos e não houve melhora na maturação do tecido gonádico da ostra nativa C. gasar submetida a diferentes dietas microalgais durante o período de acondicionamento.