Lipids and lipolytic enzymes of the microalga Isochrysis galbana

Abstract

Marine microalgae are now well-known for their ability to produce omega-3 long chain polyunsaturated fatty acids (PUFAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). Among these microalgae, Isochrysis galbana has received increasing interest especially because of its high DHA content and its common use in hatchery to feed fish larvae and clams. Moreover, lipolysis occurring from the biomass harvest stage suggests that I. galbana may contain lipolytic enzymes with potential interesting selectivities. For these reasons, the potential of this microalga for the production of valuable lipids and lipolytic enzymes was investigated. Lipid analysis revealed that DHA is mainly located at the sn-2 position of the phospholipids. Thus, I. galbana was considered as an interesting starting material for the lipase catalyzed production of 1-lyso-2-DHA-phospholipids which are considered as convenient vehicles for the conveyance of DHA to the brain. Lipids from I. galbana can also be used for the enzyme-catalyzed production of structured phospholipids containing one DHA and one medium chain fatty acid in order to combine interesting therapeutic and biological benefits. Starting from total RNA extract from I. galbana, coding sequences of putative lipolytic enzymes were obtained by RACE and Nested PCR. The heterologous expression of a sequence designated IgTeCe was implemented. An expression plasmid was constructed by ligating the coding sequence to a plasmid vector and then cloned and expressed in E. coli. Results showed the effective functionality of plasmid construction for the production of a recombinant protein with the expected molecular mass. Moreover, local alignment using BLASTP and biochemical evidences support the hypothesis that the expressed protein is a thioesterase.

Keywords

• microalgae
• ω-3 polyunsaturated fatty acids
• phospholipids
• lipolytic enzymes