Effects Of Phosphorus And Silicon On The Growth And Fatty Acid Composition Of Phaeodactylum Tricornutum

Phaeodactylum tricornutum is an ideal material for the study of polyunsaturated fatty acids because of its fast growth and reproduction,easy training and high contents of polyunsaturated fatty acids,especially EPA.Many environmental factors can effect the growth and fatty acids composition of P.tricornutum.In this suty,cell density,chlorophyll a and lutein content,fatty acid composition of P.tricornutum under phosphorus and silicon deficiency were investigated.Finally,it is importent to point out that the results of the study could be used as a mean for obtaining animal feed and EPA for industial applications.5 phosphorus concentration gradients were designed,on the basis of f/2 medium,0(0μmol/L),1/4(9.1μmol/L),1/2(18.3μmol/L),1(36.6μmol/L),2(73.2μmol/L).Cell density,chlorophyll a and lutein content and fatty acid composition of P.tricornutum under different phosphorus concentrations were investigated.One-way analysis of variance showed that phosphorus concentrations have significant effects on the cell density,specific growth rates and PUFAs and EPA percentage contens of P.tricornutum.The optimal phosphorus concentration for the growth and high production of P.tricornutu is 36.6μmol/L.The main fatty acids of this P.tricornutum are C14:0,C16:0,C16:1,C16:2,C16:3,C20:5;Furthermore,P.tricornutum was cultured to the end of exponential growth under 36.6μmol/L phosphorus concentration,then transferred to phosphate-free medium for different time phosphorus deficiency:0h,12h,24h,48h,72h,96h,phosphorus sufficient as the control.The results showed that phosphorus deficiency significantly decreased the contents of chlorophyll a,the content of chlorophyll a was 1.24ug/ml under 96h,decrease by 20.16% as the control.The increase in EPA in P.tricornutum when 12h and 48h phosphorus-deficiency,increased by 12.30% and 5.53% respectivly;The decrease in EPA in P.tricornutum when 24h and 96h phosphorus-deficiency,decreased by 20.84% and 22.01% respectivly.5 silicon concentration gradients were designed,on the basis of f/2 medium,0(0μmol/L),1/4(12μmol/L),1/2(24μmol/L),1(48μmol/L),2(96μmol/L).Cell density,chlorophyll a and lutein content and fatty acid composition of P.tricornutum under different silicon concentrations were investigated.One-way analysis of variance showed that silicon concentrations have significant effects on the cell density,specific growth rates and fatty acid composition of P.tricornutum.The optimal silicon concentration for the growth and biomass of P.tricornutu is 48μmol/L;P.tricornutum was cultured to the end of exponential growth under 48μmol/L silicon concentration,then transferred to silicon-free medium for different time silicon deficiency:0h,6h,12h,24h,48h,silicon sufficient as the control.The results showed that silicon deficiency had no significant effects on the contents of chlorophyll a and lutein but composition of fatty acids changed significantly.When 12h and 24h silicon-deficiency,the percentage contents of EPA are 20.96% and 21.86%,increased by 9.85% and 17.72% but decreased at 48h silicon-deficiency.