이매패류 먹이생물로써 미세조류 농축물 제조 최적화 연구

Abstract

Cultivated Isochrysis sp. was concentrated using two membrane filtration methods (UF / CFF) and low concentrate, high concentrate were prepared. The concentration of high concentrate was 1.70~1.77×108 Cells/mL for Isochrysis sp. and low concentrate was 3.33~4.13×107 Cells/mL for Isochrysis sp. The cell characteristics of the preserved concentrate were determined by measuring photosynthetic activity, bacterial and pH. In photosynthetic activity measurement, photosynthetic activity of Isochrysis sp. concentrate was measured to be 0 after 2 weeks of storage. In the bacterial assay, it was analyzed that the initial bacterial level were depends on initial concentration because it is not removed with water in the process of concentration and is present in the concentrate. It is also analyzed that as the pH is lowered, the bacterial levels also decrease. The pH of the concentrate tended to decrease as the storage period increased. In addition, the concentration of antibiotics (LA, HA) and the concentrates without added preservatives (LC, HC) showed similar tendency. The addition of antibiotics did not affect the pH change. To investigate the stability of the preserved concentrate, cell aggregation and fatty acid composition were investigated. In the comparison of cell coagulation degree by used membrane concentration method, concentrate using CFF was measured to maintain a certain level although the cohesion degree of the concentrate using UF increased with increasing storage period. Fatty acid analysis revealed that polyunsaturated fatty acids such as Linoleic acid (LA), Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) leaked out of the cell during storage. The field application test were conducted on oyster larvae as target organisms. The growth of larvae fed preserved microalgae was measured to be lower than that of larvae fed alive microalgae. These results suggest that the extracellular leakage of polyunsaturated fatty acids (LA, EPA, DHA, etc.)may lead to the deterioration of the feed efficacy of preserved microalgae. However, in the experiment of replacing alive microalgae, the survival period was 13 days and the average length was 124.99um when feeding alive microalgae and the survival period was 6 days, the average length was 89.23um with non-feeding. On the other hand, 90% and 95% replacement showed a significant difference (p value <0.05) from non-feeding in survaial period(12,12days) and average length(107.31um, 110.58um) Due to nutrient out and other reasons, concentrated microalgae were judged could not 100% replace alive microalgae. However, it was confirmed that concentrated microalgae could be used as food for larvae.