The objective of this project is to investigate and develop efficient microalgae biomass production methods and processes of the Nannochloropsis, Isochrysis and Hematococcus species in order to use their biomass after appropriate treatment as ingredient for high biological value fish feed production. The produced fish feeds by incorporating microalgal biomass will be evaluated for their quality and suitability for sea bass rearing.
Initially, laboratory scale experiments will be carried out to determine all parameters that will lead to the optimum performance of the microalgae biomass production process. Specifically, the effect of various conditions on the specific growth rate, and the ability to biosynthesize and produce nutrients for fishes such as proteins, amino acids, lipids (especially polyunsaturated fatty acids – PUFAs, DHA and EPA), polysaccharides and pigments (mainly astaxanthin and carotenoids from microalgae capable to biosynthesize pigments such as Isochrysis and Hematococcus) will be examined. Various factors will be studied, such as temperature, photoperiod, nutrient composition and pH. The effect of additional CO2 inflow on biomass growth and lipid accumulation in microalgae cells will be studied, as well. The produced microalgae biomass will be treated by various methods (chemical and mechanical) in order the contained nutrients to become bioavailable to fish.
Based on the results of the above-mentioned experiments a pilot scale unit, including open pond bioreactors with a total volume of 150 m3 each, will operates in an aquaculture unit. One or more strains will be selected for cultivation in pilot scale. The selection of microalgal strain for pilot scale experiments will be based on its high growth rates, high lipid content, rapid adaptation to changes and resistance to invasion by other photosynthetic microorganisms, or contamination by bacteria and protozoa. The produced biomass from pilot scale experiments will be further treated by various methods in order to increase its digestibility and nutrient availability. The most efficient treatment method will be applied to the biomass of microalgae before its incorporation in different percentages in experimental sea bass feeds. The health and growth performance of the fish fed on these feeds will be assessed and compare with the results obtained using conventional fish feed for seabass (containing high fishmeal percentages) used as control.