The Research Of Biochemical Composition Of Eight Benthic Diatoms

The main nutritious components such as: lipid, fatty acid, intracellular carbohydrate, extracellular carbohydrate, protein, ash weight and intracellular chlorophyll contents from 8 benthic diatoms isolated from coastal seawater of Dalian at 4 growth phases was measured and analyzed. Meanwhile, their growth situations on f/2 culture medium have also been observed and analyzed. Based on the development of nutritious materials and biomass, their potential as food for aquaculture and application values have been discussed.The eight benthic diatoms mentioned in the paper are: Navicula parva, Amphora. Coffeaeformis, Navicula. corymbosa, Navicula. seminulum, Amphora. proteus var. oculata, Hantzschia. amphioxys var. leptocephala, Nitzschia sp., and Rhaphoneis. surirella. Eight benthic diatoms grow differently on f/2 culture medium, Navicula. Corymbosa grows best, Nitzschia sp. grows well, but the growth situations of Rhaphoneis. Surirella and Amphora. proteus var. oculata are not well; the biomass of eight diatoms is 6.9×10~5 cells/ml-2.7×10~6cells/ml. At 8 days all eight diatoms increase sharply except Amphora. proteus var. oculata, at 15 days they reach their peak values of biomass, after 15 days the biomass has descended.The results show that the contents of protein, intracellular carbohydrate, extracellular carbohydrate, lipid, ash weight, and intracellular chlorophyll from eight benthic diatoms at 4 growth phasesare 1.21%-9.73%, 2.67%-20.76%, 2.08mg/L-16.23mg/L, 26.03%-50.71% , 18.81%-48.10% and 0.308mg/L-4.651mg/L respectively. Content of protein presented by total nitrogen is 1.62%-10.66%. Contents of Protein from Hantzschia. amphioxys var. leptocephala, Amphora. coffeaeformis, Nitzschia sp., Navicula. seminulum are higher than other diatoms, and content of protein from Hantzschia. amphioxys var. leptocephala is the highest. The contents of intracellular carbohydrate and extracellular carbohydrate from Nitzschia sp. and Amphora. Coffeaeformis are higher than other diatoms. The content of lipid from Amphora. proteus var. oculata is the highest among all diatoms. The ash weight from Navicula parva is the highest among all diatoms. The intracellular chlorophyll content of Nitzschia sp. is higher than other diatoms. The fatty acid composition differs with diatoms and growth phases, the fatty acid composition ofNavicula. Corymbosa is the most abundant, from Navicula. Seminulum, Hantzschia. amphioxys var. leptocephala, Navicula. Corymbosa, Navicula parva and Amphora. coffeaeformis EPA and DHA have been detected. In the whole growth period, the contents of intracellular carbohydrate and protein are relatively higher at 8 days and 15 days; the content of extracellular carbohydrate is increasing all through; the highest content of lipid is at 8 days; the highest ash weight is found at 3 and 25 days; at 8 and 15 days fatty acids are more relatively abundant and the contents of AA, EPA, DHA are higher.