Large-scale microalgal cultivation and use of the produced biomass as an alternative raw material in fish feed
This project will research and develop efficient methods and processes to produce biomass of the microalgal genera Nannochloropsis, Isochrysis and Hematococcus. After appropriate processing, the algal biomass will be used as a raw material in the production of fish feed of high biological value. The processed microalgal biomass will then be tested for its quality and nutritional value in seabass rearing trials where it will be applied as “standard pilot feed”.
Two experimental stages will be implemented in this project:
Α. Laboratory-scale experiments will be performed to determine the specific parameters that lead to optimal efficiency of the microalgal biomass production process. The effect of different conditions on the specific growth rate and the ability of the microalgae to biosynthesize and produce essential nutrients for fish such as proteins, amino acids, lipids (in particular polyunsaturated fatty acids – PUFAs, DHA and EPA), polysaccharides and pigments (mainly astaxanthin and carotenoids) will be examined. The effect of CO2 supply on the growth and accumulation of lipids in microalgal cells will also be studied. The biomass produced will be processed by various methods (chemical and mechanical) to ensure that the nutrients it contains are bioavailable to fish.
B. Based on the results of the above experiments, large-scale pilot microalgae cultivation will be undertaken in a local fish farm. The pilot units will comprise open tank bioreactors with a total volume of 150 cubic meters each. One or more strains will be selected from the laboratory experiments and cultured within the pilot-scale reactors. The selection criteria for these cultivated strains will be high growth rates, high nutrient yields, rapid adaptation to changes in growth conditions, and resistance to contamination by other photosynthetic microorganisms, bacteria, and protozoa-predators. The most effective method of microalgal biomass processing will be determined from the pilot-scale experiments. The biomass will then be incorporated into experimental diets of seabass in different percentages. The health and growth of these seabass will be assessed as compared to a control fed with quantities of fishmeal used in current commercial practices of seabass aquaculture.