Effect Of Environmental Factors And Inhibitors On Fatty Acid Biosynthesis In Phaeodactylum Tricornutum

Phaeodactylum tricornutum is an important oil-producing microalgae, contains much unsaturated fatty acids. To probe the effect of the environmental factors and specific desaturase inhibitors on the growth and the fatty acid biosynthesis of Phaeodactylum tricornutum a series of experiments were carried out. And the preliminary cloning of delta5fatty acid desaturase and delta6fatty acid elongase of Phaeodactylum tricornutum also was researched. The results were listed as follows:1. The net increase of the cell numbers of Phaeodactylum tricornutum reached the maximum at the middle inoculative densities(150×104个ml); and the relative growth rate was decreased with increasing of the density (from150×104个/ml to250×104个/ml).2. The growth and fatty acid contents reached the maximum at salinity30%o; the photosynthesis was not different obviously from salinity20%o to40%o; the growth and fatty acid biosynthesis of Phaeodactylum tricornutum were inhibited by varying degrees at salinity from15%o to25%o and from35%o to55%o, and the cells died gradually at salinity from1%o to10%o.3. The growth, photosynthesis and fatty acid biosynthesis reached the maximum at pH8; The biomass and fatty acid contents were increased with increasing of pH(from6to7.5); the photosynthesis was increased first and then decreased with increasing of pH(from6to7.5); the biomass, photosynthesis and fatty acid contents were decreased with increasing of pH(from8.5to10).4. The greatest value of biomass, photosynthesis, fatty acid contents and nutrient assimilation efficiency were obtained at urea as nitrogen source;there were significantly different compare to sodium nitrate and ammonium chloride as nitrogen source. 5. The N, P and SI single factor experiment and the orthogonal experiment showed that the biomass, photosynthesis and fatty acid contents were decreased with slightly high concentration of N and P; the biomass and fatty acid contents were increased with appropriate concentration of SI. The greatest value of biomass, photosynthesis, fatty acid contents and nutrient assimilation efficiency were obtained at N:1.45mmol/l,P:109.5μmol/l,SI:418μmol/l.6. At propyl gallate concentration of0.01g/1, the biomass, fatty acid contents, Ci6and C18fatty acid percentage were increased, C22and C24fatty acid percentage were were decreased, the growth was inhibited by acrylic acid, however, the fatty acid profile and percentage were least affected by the acrylic acid. The biomass and fatty acid contents were decreased by the linoleic acid, but the C16and C18fatty acid percentage were increased.7. The results of the DNA sequence analysis showed that the DNA of delta6fatty acid elongase was1001bp, contained three expressed regions and two introns in Phaeodactylum tricornutum.