【作者】 蒋汉明；

【导师】 高坤山；

【作者基本信息】 汕头大学 ， 环境科学， 2003， 硕士

【摘要】 为了探讨微藻生产多不饱和脂肪酸（polyunsaturated fatty acids，PUFAs）的最适条件，本文以三角褐指藻（Phaeodactylum tricornutum）和等鞭金藻（Isochrysis galbana）为材料，研究了不同培养条件下两种微藻的生长和PUFAs含量变化。 三角褐指藻的最适生长温度为20℃，当培养温度超过25℃时，其生长受到明显的抑制。等鞭金藻适宜的温度范围为25～30℃，温度低于15℃，生长缓慢。降低培养温度提高了三角褐指藻EPA（eicosapentaenoic acid）和PUFAs含量，10℃时，EPA和PUFAs的含量分别比25℃时提高了90％和50％。等鞭金藻细胞中的DHA（docosahexaenoic acid）含量变化也表现出相同的趋势，但其PUFAs含量在20℃达到最大。在一定光强范围内，两种微藻比生长速率随着光强增加而增加。两种微藻在光强为80μmol m^-2s（-1）时，比生长速率最大，分别为0.86和0.81d^-1。随着光强的增加，三角褐指藻EPA和PUFAs的含量下降，而等鞭金藻DHA和PUFAs含量则表现相反的趋势，130μmol m^-2s（-1）时二者的含量分别比30μmol m（-2）s^-1时增加了110％和16％，在210μmol m（-2）s（-1）出现下降。 氮源的种类和浓度均影响三角褐指藻和等鞭金藻的生长与PUFAs的合成。氮浓度低于1.80mM时，三角褐指藻以NH₄⁺为氮源生长最快；氮浓度高于3.50mM时，以NH₂CONH₂为氮源生长最快。等鞭金藻以NH₂CONH₂为氮源生长最快，对NH₄⁺比较敏感，当NH₄⁺浓度高于0.90mM时，其生长就受到抑制。无论是哪种氮源，三角褐指藻EPA含量均随着氮浓度的增加而升高。PUFAs含量随着NO₃^-浓度增加而降低，随着NH₂CONH₂浓度增加而上升，而几乎不受NH₄⁺浓度的影响。以NH₄⁺或NH₂CONH₂为氮源，等鞭金藻DHA含量在1.80mM时达到最高；以NO₃^-为氮源，在3.50mM时最高。氮浓度为0.01mM时，EPA或DHA合成受阻，从而导致三角褐指藻中C_{18:2（n-6）}、C_{18:3（n-6）}和等鞭金藻中C_{18:2（n-6）}积累。 随着磷浓度的增加，三角褐指藻比生长速率增加；对等鞭金藻来说，当磷浓度高于39μM时，其比生长速率呈下降趋势。磷浓度越高，三角褐指藻EPA和PUFAs含量越低。虽然磷浓度为3μM时，二者含量最高，但生物量最低。等鞭金藻DHA含量随磷浓度的增加而上升，75μM时达到最大，但PUFAs含量随磷浓度的增加而下降。 Fe³⁺缺乏，对两种微藻的生长具有不同程度的限制作用。当Fe³⁺浓度高于24.5μM时，对三角褐指藻的生长表现出抑制作用，但对等鞭金藻的生长没有影响。随着Fe³⁺浓度的增加，三角褐指藻的EPA和PUFAS含量逐渐下降。等鞭金藻DHA和PU队s含量随Fe3+浓度的增加先上升后下降，二者达到最大时的Fe3+浓度分别为60.5林M和24.5抖MO 高co:浓度能显著地促进两种微藻的生长。高co:浓度（20000 ppmv，2%）条件下，三角褐指藻EPA和PUFAs含量分别比对照（350 ppmv）提高了1 .3和1 .9倍;等鞭金藻在高CO:浓度下，DHA含量比对照下降了29%，但PUFAS含量比对照提高了35%。可见，提高CO:浓度可有效的调控微藻多不饱和脂肪酸的合成。 从生产的角度来看，三角褐指藻培养在150c，光强为80林molm一“S一，，以7.00 mM的NHZe州H:为氮源，75林M的N出ZPo;为磷源;Fe3+浓度为12.5林M并加富eoZ可以获得最高的EPA和PuFAs产量。等鞭金藻在200c，光强为130林molm一S一，，以1.somM的NHZeoNH:为氮源，39oM的NaHZPo;为磷源;Fe，+浓度为24.5协M并加富CO，可以获得最高的DHA和PUFAs产量。更多还原

【Abstract】 Two species of marine microalgae, Phaeodactylum tricornutum and Isochrysis galbana were cultured in batch under various conditions and their growth and polyunsaturated fatty acids (PUFAs) contents were investigated in order to optimize their PUFAs production.P. tricornutum grew best at 20℃ and its growth was significantly inhibited when temperature exceeded 25℃. /. galbana grew better at 25~30℃, but poorer below 15℃. EPA (eicosapentaenoic acid) and PUFAs contents based on dry mass were elevated by lowered temperature in P. tricornutum. Their contents increased by 90% and 50% at 10℃ compared with that at 25℃. DHA (docosahexaenoic acid) content in I. galbana showed the same tendency, but its PUFAs content reached the maximum at 20℃. The specific growth rate (μ) increased with increased light intensity and reached the maximal values of 0.86 d-1 in P. tricornutum, and 0.81 d-1 in /. galbana at 80μ mol m-2 s-1. EPA and PUFAs contents of P. tricornutum decreased as light intensity level was raised, however, those of /. galbana were raised by 110% and 16%, respectively, at 130 μ mol m-2 s-1 compared with that at 30 μ mol m-2 s-1, then decreased at light levels above 210μ mol m-2 s-1.Nitrogen sources and concentrations not only affected the growth but also PUFAs production of the two species of algae. At lower nitrogen concentrations (<1.80 mM), P. tricornutum showed better growth with NH4+, however, it grew faster with NH2CONH2 at higher concentrations (>3.50 mM). /. galbana grew fastest with NH2CONH2, but its growth was inhibited when NH/ concentration exceeded 0.90 mM. EPA content in P. tricornutum increased with increased nitrogen concentration within a range of 0.90 to 7.00 mM regardless of the nitrogen sources. Its PUFAs content decreased with NO3-, increased with NH2CONH2, but changed little with NH4+ as their levels were raised. DHA content in /. galbana showed the highest yield at 1.80 mM with NH4+ or NH2CONH2 and at 3.50 mM with NO3-. The biosynthesis of EPA and DHA was suppressed without nitrogen enrichment, resulting in the accumulation of C18:2(n-6) and C18:3(n-6)in P. tricornutum and C18:2(n-6) in /. galbana.The specific growth rate (μ) of P. tricornutum increased as the H2PO4 level was raised, but that of I, galbana decreased when the H2PO4- concentration was higher than 39 μM. In P. tricornutum, higher H2PO4- concentrations brought about lower EPA and PUFAs contents.tricornutum, higher H2PO4 concentrations brought about lower EPA and PUFAs contents. Although the highest EPA and PUFAs contents were obtained at 3 μM H2PO4-, the biomass yield was the lowest. DHA content in I. galbana increased with the increased H2PO4-concentrations and reached the maximum at 75 uM, however, its PUFAs content declined straightly.Fe3+ deficiency limited the algal growth. However, Fe + overdose (>24.5μM) was harmful to P. tricornutum, though it had little influence on /. galbana. Lower EPA and PUFAs contents of P. tricornutum were associated with higher Fe3+ levels. /. galbana showed the highest DHA and PUFAs contents at 60.5 uM Fe3+ and 24.5 uM Fe3+, respectively.CO2 enrichment in aeration enhanced the growth of the two algae With 2% CO2 (20000 ppmv), EPA and PUFAs contents of P. tricorntum increased respectively 1.3 and 1.9 times and that of DHA decreased by 29%, but PUFAs increased by 35% in /. galbana. It was found that elevation of CO2 concentration was an effective way for regulating PUFAs production.From the view point of PUFAs production, it was concluded that P. tricornutum cultured under the conditions of 15℃, 80 μmol m-2 s-1, 7.00 mM NH2CONH2, 75μM H2PO4-, 12.5 uM Fe3+ and enrichment CO2 could generate high EPA and PUFAs yields. High DHA and PUFAs outputs by /. galbana were obtained at 20℃, 130 μmol m-2 s-1, 1.80 mM NH2CONH2, 39 μM H2PO4- and 24.5 uM Fe3+ in CO2-enriched culture.更多还原