自养小球藻转化为异养代谢生长后细胞的超微结构与相关生化组成

利用细胞培养技术转化绿色自养的小球藻(Cholrella protothecoides)进行异养生长代谢.酶法分析反映,异养转化过程中细胞培养液中葡萄糖的利用率很高。转化后的细胞光合片层消失,叶绿体同时消失,细胞被一些大的酯肪泡填充,异养藻细胞的细胞壁也比原自养藻细胞加厚,而且细胞表而发生皱缩现象。再次将异养藻细胞置于自养生长条件下,细胞的光合片层和叶绿体结构又得以重建。生化分析显示,经异养转化后藻细胞蛋白质含量下降,为原绿色自养细胞的1/5;相反脂肪含量大幅度增加,是原初的4.4倍,达到细胞干重的72.％。异养藻细胞样品各氨某酸含量都低于自养藻细胞样品,前者以谷氨酸含量较高,后者含甘氨酸最多。在自养藻细胞样品中亚油酸的相对含量最高,为56.50％;转化为异养生长后变成油酸的相对含量占优势,达69.36％,说明异养转作用可明显降低细胞中脂防酸的不饱和程度。

FINE CELL STRUCTURE AND BIOCHEMICAL COMPOSITIONS OF CHLORELLA PROTOTHECOIDES AFTER TRANSFERRING FROM AUTOTROPHIC TO HETEROTROPHIC METABOLISM

By cell culture technology, the green autotrophic cells of Chlorella protothecoides (American strain) were transferred to heterotrphic metabolic growth and the yellow chlorophyll-less cells were obtained. The glucose-absorbance rate of the heterotrophic cells in the medium was very high. It was found by electron microscopic observation that both lamellate structure of photosynthesis and chloroplast in yellow heterotrophic cells disappeared. And the cells were filled with large lipid vacuoles. The cell wall of heterotrophic algae was thicker and more wrinkled than that of autotrophic one. The lamellate structres of both photosynthesis and chloroplast were regenerated, and meanwhile no lipid vacuoles were observed when these heterotrophic cells were transferred back to autotrophic growth conditions. The analysis of biochemical compositions showed that after being transerred from autotrophic to heterotrophic growth, the amount of protein in cells decreased, which was only one fifth of that in green autotrophic cells. However, the content of lipid increased greatly to 72% of the dry weight of the cells, which was 4.4 times that of green autotrophic cells. The amount of amino acids in heterotrophic cells was less than that in autotrophic cells. The former contanined more glutamic acids and the latter was rich in glycine. The compositions and relative contents of fatty acids also remarkably different in two kinds of cells. Especially heterotrophic cells contained a large amount of oleic acid which accounted for 69.36% in total fatty acids. The-small amount of fatty acids in autotrophic cells showed a high degree of unsaturation, in which linoleic acid had a high relative percantage (56.50%). This suggested that heterotrophic transferation decrease the unsaturation degree of the fatty acids in algal cells. The results show that studies on algal heterotrophic metabolism are of great significance in experimental biology and in applied cell engineering.