Biomass production and biochemical composition in mass cultures of the marine microalga Isochrysis galbana Parke at varying nutrient concentrations |
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| Institution: | 1. Advance Technology Development Center, Indian Institute of Technology, Kharagpur, 721302, India;2. Department of Biotechnology, Indian Institute of Technology, Kharagpur, 721302, India;1. Plant Cell Biotechnology Department, CSIR-Central Food Technological Research Institute (CFTRI), Mysore 570 020, India;2. Sensory Sciences Department, CSIR-Central Food Technological Research Institute (CFTRI), Mysore 570 020, India;3. Oil and Natural Gas Corporation Limited (ONGC), Keshava Deva Malaviya Institute of Petroleum Exploration (KDMIPE), 9 Kaulagarh Road, Dehradun 248 195, India;1. Marine Bioengineering Group, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. School of Life Science and Biotechnology, Dalian University of Technology, Dalian 116024, China;4. State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China |
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| Abstract: | 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. |
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