Isolation of Chloroplasts from Marine Microalga Isochrysis galbana Parke for Their Lipid Composition Analysis

• 作者: ZHONG Ye LI Yanrong XU Jilin CAO Jiayi ZHOU Chengxu YAN Xiaojun
• 来源期刊: 中国海洋大学学报（自然科学英文版）
• 年，卷（期）: 2022,（1）
• 所属期刊栏目: Life and Fisheries Sciences
• 页码范围: 225-235
• 页数: 11页
• 语种: 英文

摘要

Marine microalga Isochrysis galbana is an important feed species with a high nutritional value. Different from other uni- cellular algae, its cell contains two chloroplasts which are the major sites for lipid synthesis. Here, we optimized a chloroplast isola- tion approach suitable for the isolation of I. galbana chloroplasts and determined the purity and integrity of the isolated chloroplasts through microscopic observations and enzyme activity assay. The chloroplast lipids were analyzed with a ultrahigh-performance li- quid chromatography-Q Exactive Orbitrap-mass spectrometry. This newly developed isolation approach is simple and reliable to isolate chloroplasts with high integrity and purity. The average yield of intact chloroplasts was 15.3％ ± 0.1％. Glycolipids and acyl- glycerols were the main chloroplast lipids. Glycolipids accounted for 56.6％ of chloroplast lipid. Digalactosyldiacylglycerol (DGDG), monogalactosyldiacylglycerol (MGDG) and sulfoquinovosyldiacylglycerol (SQDG) were the main glyceroglycolipids. The fatty acyl R1/R2 were mostly 18:4/16:1, 18:3/16:1 and 18:4/18:5 in DGDGs, 14:0/18:4, 18:4/18:5, 18:4/18:4 and 18:3/18:4 in MGDGs and 16:0/14:0, 16:0/18:3, and 18:4/18:3 in SQDGs. In addition, diacylglycerol (DAG) was the most abundant acylglycerols; the content of 22:6/18:4-DAG was the highest. There was a little amount of glycosphingolipid (GSL) in chloroplast. Digalactosylmonoglyceride (DGMG), monogalactosylmonoglyceride (MGMG), sulfoquinovosylmonoacylglycerol (SQMG), monoglyceride (MAG), phospholi- pids (PLs), ceramide (Cer) and betaine lipids were nearly undetectable in chloroplast. The fatty acid proportions of DGDGs, MGDGs, SQDGs, DAGs, triglycerides (TAGs) and GSLs were either higher or lower than or similar to those of whole-cell. Collectively, our isolation approach is applicable to many aspects of chloroplast biology, and may offer a reference for the isolation of chloroplasts from other marine microalgae.