The influence of temperature and nutrient concentrations on growth rate, biomass, Chlorophyll-a, and biochemical compositions of Tetraselmis suecica (Chlorophyta)

Microalgae have been got high attention due to its potentiality in aquaculture as live feed, and in industries as ingredients for pharmaceutical, cosmetics, and biofuel industries. The objective of this study was to know the optimum culture condition for profuse growth and biochemical composition of Tetraselmis suecica under two parameters: temperature (20°C, 25°C, and 30°C) and modified F/2 medium nutrients concentrations. Culture of group “A” 20°C was categorized as A1 (F/2 stock solution-A; 0.50 ml. L-1 and F/2 stock solution-B; 0.20 ml. L-1), A2 (F/2 stock solution-A; 1. 00 ml L-1 and F/2 stock solution-B; 0.40 ml. L-1) and A3 (F/2 stock solution-A;1.50 ml. L-1 and F/2 stock solution-B; 0.60 ml. L-1). Cultures in 25°C and 30°C were also categorized as groups “B” 25° C (B1, B2, and B3) and “C” 30°C (C1, C2, and C3), respectively. The culture was done for 2 weeks with L:D cycle of 12:12 by using fluorescent light. The highest biomass production was 0.80, 0.64, and 0.45 gL-1 in C2, B3, and A3, respectively. Biochemical analysis showed that protein; 21.92, 20.83, and 18.68 %, lipid; 10.76, 9.42, and 11.71 %, carbohydrate; 38.51, 37.78, and 41.49 %, ash; 15.89, 15.61, and 13.7 %, and moisture; 14.26, 15.02, and 14.42 % in biomass grown of “A”, “B” and “C” culture group, respectively. From the study, it could be said that T. suecic is a eurythermal and mesotrophic habitant microalga which produce high protein and high carbohydrate in low and high temperature, respectively.

Gibberellic Acids Promotes Growth and Exopolysaccharides Production in Tetraselmis Suecica Under Reciprocal Nitrogen Concentration: An Assessment on Antioxidant Properties and Nutrients Removal Efficacy of Immobilized Iron-magnetic Nanoparticles

The present study was aimed to assess the effect of gibberellic acids to enhance the growth, biomass, pigment, and exopolysaccharides production in Tetraselmis suecica under reciprocal nitrogen concentrations. For this study, the seven types of experimental media (N-P, NL-P/2GA3, N0-P/2GA3, NL-P/4GA3, N0-P/4GA3, NL-P/6GA3, N0-P/6GA3) were prepared include the addition of gibberellic acids under various nitrogen concentrations. The experiment was lasted for 15 days and the cell density, biomass, chlorophyll ‘a’, and exopolysaccharides (EPS) concentration of T. suecica were estimated for every three days. Then the EPS was subjected to the analyses of chemical (carbohydrate, protein, sulfate, and uronic acid), and antioxidant activity. In addition nutrient removal efficiency was evaluated by using different concentration of EPS. The highest DPPH (86.7±0.95 %) and hydroxyl radical activity (85.7±2.48 %) were observed in 2.5 and 1.2 mg/mL of EPS concentration. The immobilized magnetic Fe3O4-EPS nanoparticles (5.0 and 10.0 g/L) have efficiently removed the excessive phosphate (89.5±1.65 %) and nitrate (73.5±1.72 %) from the Litopenaeus vannamei cultured wastewater. Thus, applying gibberellic acids combined with limited nitrogen concentration could produce higher EPS that could exhibit excellent antioxidant activity, and nutrient removal efficacy in the form of Fe3O4-EPS magnetic nanoparticles.

Effect of light intensity and nutrient concentration on growth and pigments of the green microalga Tetraselmis suecica

Tetraselmis suecica is a green microalga that thrives under a wide range of conditions, used in the commercial culture of fish, mollusk, and crustacean larvae for supplementing the demand for fertilizers. Its pigments have applications in human health care as drug products, vitamins, and cosmetics. Growth and pigment concentration of T. suecica were evaluated in experimental cultures with different nutrient concentrations and light intensities to determine the most appropriate culture conditions to optimize the production of biomass and pigments. Chlorophyll-a, chlorophyll-b, lutein, violaxanthin, α, β-carotene, and neoxanthin concentrations were evaluated under three different nutrient conditions (441.5/18.1, 883/36.3, and 1766/76.2 μM of NaNO3/NaH2PO4) and four light intensities (50, 150, 300, and 750 μmol quanta m-2 s-1). Increases in either or both of these factors lead to increases in the concentration of all pigments. Chlorophyll-a reached up to 5×103 mg m-3, chlorophyll-b up to 2500 mg m-3, lutein 600 mg m-3, violaxanthin 300 mg m-3, α, β-carotene 500 mg m-3, and neoxanthin 400 mg m-3. Growth rate (μ) attained values of 1.6 d-1. An index to evaluate the efficiency of pigment production by light intensity (called LER) was computed. The highest LER was recorded at 50 μmol quanta m-2 s-1 and a nutrient concentration of 1766/76.2 μM (NaNO3/NaH2PO4); this treatment optimizes pigment production with the lowest light intensity. Our results show that the optimum light intensity should be selected according to the objective of the culture, either maximizing pigment concentration for harvesting at higher concentrations or reducing production costs regarding light consumption.

Changes in Free-Living and Particle-Associated Bacterial Communities Depending on the Growth Phases of Marine Green Algae, Tetraselmis suecica

Bacteria are remarkably associated with the growth of green algae Tetraselmis which are used as a feed source in aquaculture, but Tetraselmis-associated bacterial community is characterized insufficiently. Here, as a first step towards characterization of the associated bacteria, we investigated the community composition of free-living (FLB) and particle-associated (PAB) bacteria in each growth phase (lag, exponential, stationary, and death) of Tetraselmis suecica P039 culture using pyrosequencing. The percentage of shared operational taxonomic units (OTUs) between FLB and PAB communities was substantially high (≥92.4%), but their bacterial community compositions were significantly (p = 0.05) different from each other. The PAB community was more variable than the FLB community depending on the growth phase of T. suecica. In the PAB community, the proportions of Marinobacter and Flavobacteriaceae were considerably varied in accordance with the cell number of T. suecica, but there was no clear variation in the FLB community composition. This suggests that the PAB community may have a stronger association with the algal growth than the FLB community. Interestingly, irrespective of the growth phase, Roseobacter clade and genus Muricauda were predominant in both FLB and PAB communities, indicating that bacterial communities in T. suecica culture may positively affect the algae growth and that they are potentially capable of enhancing the T. suecica growth.

Optimization of Lutein Recovery from Tetraselmis suecica by Response Surface Methodology

Microalgae have been attracting attention as feedstock for biorefinery because they have various advantages, such as carbon fixation, high growth rate and high energy yield. The bioactive compounds and lutein contained in microalgae are known to be beneficial for human health, especially eye and brain health. In this study, in order to improve the recovery of bioactive extracts including lutein from Tetraselmis suecica with higher efficiency, an effective solvent was selected, and the extraction parameters such as temperature, time and solid loading were optimized by response surface methodology. The most effective solvent for lutein recovery was identified as 100% methanol, and the optimum condition was determined (42.4 °C, 4.0 h and 125 g/L biomass loading) by calculation of the multiple regression model. The maximum content of recovered lutein was found to be 2.79 mg/mL, and the ABTS radical scavenging activity (IC50) and ferric reducing antioxidant power (FRAP) value were about 3.36 mg/mL and 561.9 μmol/L, respectively. Finally, the maximum lutein recovery from T. suecica through statistical optimization was estimated to be 22.3 mg/g biomass, which was 3.1-fold improved compared to the control group.