| The benthic diatoms are essential food source for precious marine economic animals such as abalone and sea cucumber etc. It has very important significance to isolate the good benthic diatoms food from nature for the local aquacultμre which produce marine economic animal seedlings.In the paper, benthic diatoms were collected by scraping sand and filtering in Lianjiang maritime space in Fujian. The biological characteristics, culture conditions and the impact factors which affect the metabolic products of the one isolated benthic diatom were studied to investigate the potential application value as food for aquaculture and to afford the theoretical basis for a large scale and high density cultivation. Besides, the immobilization culture of benthic diatom, germplasm conservation and algal-bacterial co-immobilization with the embedding techniques were researched. The results in detail were stated as follows:1. Three benthic and two planktonic diatoms were acquired by spreading plating method.One of the benthic diatoms was identified as Nitzschia constricta by morphology observation.The nutritional ingredient analysis indicate that the crude protein level was 7.26%, and the essential amino acid was 43.12% of the total amino acids, and glutamic acid was 14.56%; the unsaturated fatty acid was 48.3% of the total fatty acid. Compare to other common food diatoms, it's very fit the food requests of marine economic animals such as abalone and has the good economic food value.2. By evaluating the pigments, growth rate and dry weight, the favourable and optimum culture conditions of N. constricta are temperature 18-30℃,salinity 10-45‰, pH 6-10 and light intensity 500-1000 lx,which has the wide subject range in the water.The nitrogen,phosphorous,iron and silicon concentrations indicate that N. Constricta grow well at NO3-N 14.13 mg/L,NaH2PO3-P 0.87 mg/L and the optimum ferric citrate-Fe and silicon concentrations was 0.07-1.3 g/1,0.23-23 mg/L.3. The protein and exopolysaccharide yield of N. Constricta under the different culture conditionds demonstrate:the temperatμre has no positive effect on protein produce, but is positive to exopolysaccharide yield which has the most content 6.93μg/ml at 24℃. There is no evident difference of protein yield in days when the salinity exceeds 10‰,but the exopolysaccharide yield the most of 8.40μg/ml at salinity 30‰.The pH changes in the cultμre solution has no regular effects to exopolysaccharide yield.It has good protein and exopolysaccharide accumμlation at pH≤8.When Sodium Nitrate is 75 mg/l,the highest protein content 28.9μg/ml was obtained at the 10th day, and the exopolysaccharide yield was increased with the cultμre time prolonged.The protein was increased at the higher phosphoroμs concentrations,bμt the limited phosphoroμs was good for exopolysaccharide yield at the early days.When the ferric citrate was 3.9 mg/l,the most protein was obtained at the 15th day,but the iron change has no evident effect to exopolysaccharide yield.The lower silicon concentration the more exopolysaccharide yield of N. Constricta, and the most is 10.64μg/ml,but the silicon changes has no evident effect to protein yield.4. The benthic diatoms immobilization was researched by alginic acid embedding techniqμe. The Orthogonal test design showed that the inoculation density 107 cell/ml, alginate 4%, Calcium Chloride 3% are the optimized conditions for immobilizated N. Constricta growth. The reculture N. Constricta immobilizated for 90 days still has the good viability; compared to control, the protein and exopolysaccharide yield have no dofferent.Tt also found that the low and room temperature are both appropriate for N. Constricta conservation by cell counting and fluoremetry of confocal laser scanning microscope.5. The attempt of N. Constricta, Navicula sp., Phaeodactylum Tricornutum co-immobilization with marine yeast were carried.lt found algal-bacterial co-immobilization can promote the diatoms growth.
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