The Optimization Of Micro-algae Culture Conditions And Its Effect On The Growth And Development Of Artemia Sp.

Micro-algae are the important primary productivity of ecosystems,and have been widely used in food,feed,medicine,chemical industry and dyes.In the aims to increase the yield of microalgae cells or target substances,we can monitor and optimize the level of nutritive substances in culture medium to enhance the utilization rate by optimizing the sources and concentrations,which should be one of fundamental points for high efficiency,low cost,and large-scale cultivation of microalgae.In this study,with the aims to increase cell production and accumulation of intracellular substances in marine micro-algae,the nitrogen sources and the initial concentrations of nitrogen and phosphorus were studied to clarify their effects on marine micro-algae.Dunaliella salina and Chaetoceros gracilis were employed as the typical marine micro-algae for clarification of the effects of nutritive salts on their growth and accumulation of intracellular substances.With the consideration of growth,accumulation of intracellular substances,costs for scale cultivation,the suitable and optimized the sources and concentrations of nutritive salts were examined.At the same time,the changes of the relationship between proteins,sugars and total lipids in marine micro-algae cells were also studied.In addition,combined with illumination conditions,the growth,development and reproduction of Artemia sp.fed with marine microalgae of different intracellular substances proportion were followed and compared.The main experimental results of this study are as follows:(1)The cell growth and final biomass of D.salina was affected by nitrogen concentration by similar trend.D.salina achieved the best growth and highest final biomass with nitrogen concentration of 882.46?g/L.The best nitrogen concentration for intracellular protein accumulationwas 882.46 g/L.In the cases of sugar and total lipid contents,there was no significant difference between the treatments with various nitrogen concentrations.With the joint consideration of cell growth and accumulation of intracellular substance together,nitrogen concentration of 882.46 ?g/L was proposed for the productive applications.(2)In terms of high biomass and protein content,phosphorus concentration of 64.10?mol/L was proposed.And phosphorus concentration of 4.01?mol/L was suggested to achieve higher content and more abundant lipid or sugar.(3)The best nitrogen source for the growth of D.salina was CH4N2O,which makes us believe that CH4N2O should be an idea nitrogen source for the scale cultivation of D.salina.,The lowest concentration of 200 ?mol/L CH4N2O was suggested for scale cultivation in order to reduce the cost.The next suitable nitrogen source for D.salina growth was NO3--N,while the worst growth of D.salina was observed in the treatments using NH4+-N,what the final biomass was very low.Significant difference in sugar and lipid contents was not observed among the treatment using different nitogen concentrations but observed among the treatment using different nitrogen sources.The best nitrogen source for accumulation of sugar was NH4Cl or NaNO3,while the best one for lipid accumulation was NH4Cl.The protein content of D.salina was significantly affected by nitrogen concentration,but the same was not true for nitrogen source.The higher nitrogen concentration led to the higher the protein accumulation.Since growth of D.salina was affected by nitrogen source and concentration,200 ?mol L-1 of CH4N2O was proposed for D.salina with the additional consideration of cost.(4)The highest cell growth and final biomass were both observed in the treatment of 880.46 ?mol/L nitrogen.For the aims of high contents of lipid,protein and sugar in of C.gracilis cells,the proposed optimal nitrogen concentrations are 110.31 ?mol/L,1764.91 ?mol/L,1764.91 ?mol/L,respectively.(5)The highest cell growth and final biomass were both observed in the treatment of 96.15?mol/L phosphorus concentrations.For the aims of high biomass,protein content,and sugar + lipid content,the proposed optimal phosphorus concentration is 96.15 ?mol/L,8.01?mol/L,and 4.01?mol/L or 8.01?mol/L,respectively.With the joint consideration of appropriate content intracellular substances and biomass,the phosphorus concentration of 8.01 g/L was proposed as a suitable concentration for C.gracilis.(6)The results indicate that the body length of Artemia sp.was affected by lipid content more significantly than protein content in C.gracilis cells.The survival rate of Artemia sp.was only 45.5%fed with low lipid and high protein C.gracilis cells under the condition without illumination.The survival rate of Artemia sp.with illumination was 69.5%and the reproduction ability was also significantly enhanced when being fed with cells of high lipid content.