Assessment on the oil accumulation by knockdown of triacylglycerol lipase in the oleaginous diatom Fistulifera solaris

Abstract

Microalgae are promising producers of biofuel due to higher accumulation of triacylglycerol (TAG). However, further improvement of the lipid metabolism is critical for feasible application of microalgae in industrial production of biofuel. Suppression of lipid degradation pathways is a promising way to remarkably increase the lipid production in model diatoms. In this study, we established an antisense-based knockdown (KD) technique in the marine oleaginous diatom, Fistulifera solaris. This species has a capability to accumulate high content of lipids. Tgl1 KD showed positive impact on cell growth and lipid accumulation in conventional culture in f/2 medium, resulting in higher oil contents compared to wild type strain. However, these impacts of Tgl1 KD were slight when the cells were subjected to the two-stage growth system. The Tgl1 KD resulted in slight change of fatty acid composition; increasing in C14:0, C16:0 and C16:1, and decreasing in C20:5. This study indicates that, although Tgl1 played a certain role in lipid degradation in F. solaris, suppression of only a single type of TAG lipase was not significantly effective to improve the lipid production. Comprehensive understanding of the lipid catabolism in this microalga is essential to further improve the lipid production.

Bioinformatics-Based Screening Approach for the Identification and Characterization of Lipolytic Enzymes from the Marine Diatom Phaeodactylum tricornutum

“…Indeed, the fatty acid profile of P. tricornutum TAG is mainly composed of medium and long-chain fatty acids (C14:0, C16:0 and C16:1) [ 55 ] which is in line with GX type lipases that could degrade them. For patatin-like phospholipases, even though their oxyanion hole motif resembles a GGGX type, some homologs from different microalgae have been shown to hydrolyze TAG with long to very long chain fatty acids [ 30 , 43 , 45 , 56 ].…”

“…In these studies, a knockdown of the lipase gene led to an increase in lipid accumulation while slightly affecting the cell density reached at the stationary phase, either by enhancing (+17%), or by decreasing it (−6 to −10%). Additional studies have been conducted on other diatoms with the knockdown of a CGI-58 homolog in Thalassiosira pseudonana [ 42 ] and of a tgl1 homolog in Fistulifera solaris [ 43 ], both showing an increase in lipid accumulation while not affecting division rate [ 42 ] or even enhancing it [ 43 ]. This inactivation approach therefore allows to obtain strains displaying a high lipid productivity.…”