Production of free fatty acids in marine phytoplankton

在20 ℃分批培养系统中，测定了三角褐指藻和赤潮藻异弯藻的游离脂肪酸（FFA）和磷脂酶A（PLAaseA）活性，发现三角褐指藻在对数生长中期、稳定期早期和稳定期晚期的FFA分别占总脂的16%、29%和46%。沿着大量的极性脂质（PL）和少量的三酰基甘油（TG）、烃和甾醇。在较低的温度（5 ℃）下，各生长期的FFA含量分别降低至1、18和32%。在与三角褐指藻相同的培养体系中，20 ℃培养的赤潮红球藻各生长期的FFA含量仅占总脂的2-4%，而PL含量沿着上升，达到90%以上。TG仅在静止期晚期出现，占总脂的3%。FFA的主要成分为16：0和20：5（n-3）。这些脂肪酸主要分布在sn-1位置的monogalactosyldiacylglycerol分子，这是一个主要的脂质类的H. akashiwo。另一方面，在磷脂酰胆碱分子中，20：5（n-3）分布在sn-1和sn-2两个位置。从三角褐指藻和赤藻制备的丙酮粉末显示出对二油酰磷脂酰胆碱的PLaseA活性，几乎没有检测到对TG的脂肪酶活性。因此，两种植物脂素中的游离脂肪酸似乎主要由PLaseA从PL中释放出来。

Determination of made of free fatty acids (FFA) and phospholipase A (PLaseA) activity in the diatom Paeodactylum tricornutum and the raphidophyte flagellate Heterosigma akashiwo, which is a causative phytoplankton of red tides.P.tricornutum in the mid-logarithmic phase, early stationary phase and late stationary phase in a batch culture system at 20C was found to contain 16,29 and 46% FFA of total lipid, along with larger amounts of polar lipids (PL) and smaller amounts of triacylglycerols (TG), hydrocarbons and sterols. At a lower temperature (5C), the FFA content in each growth phase was reduced to 1,18 and 32%, respectively. FFA composition was characterized by much 20 : 5 (n-3).H.akashiwo in the same culture system as P.tricornutum at 20C was found to contain only 2-4% FFA of total lipid in each growth phase, along with PL of more than 90%. TG was contained only in the late statinary phase, accounting for 3% of total lipid. Major components of FFA were 16 : 0 and 20 : 5 (n-3). These fatty acids were predominantly distributed in the sn-1 position of monogalactosyldiacylglycerol molecules, which were a major lipid class of H.akashiwo. In phosphatidylcholine molecules, on the other hand, 20 : 5 (n-3) was distributed in both sn-1 and sn-2 positions.Acetone powders prepared from P.tricornutum and H.akashiwo showed PLaseA activity toward dioleoylphosphatidylcholines and virtually no lipase activity for TG could be detected. Free fatty acids in the both phytoplanktons would thus appear to released primarily from PL by PLaseA.The greater activity of PLaseA1 compared to PLaseA2 is discussed.