Response Surface Optimization of Enzyme Pretreatment Improves Yield of Ethanol‐Extracted Lipids from Nannochloropsis oceanica

Nannochloropsis oceanica are marine microalgae that are rich in eicosapentaenoic acid (EPA); in the future, they may become one of the most effective sources of EPA. The cell walls of N. oceanica contain a three-layered dense structure called algaenan, which hinders the extraction of intracellular lipids. Here, the main variables for the enzyme pretreatment of N. oceanica are optimized using response surface methodology. Under the optimal variables for enzyme pretreatment, the lipid yield and EPA content are increased to 26.9% and 20.7 g/100 g, respectively. Furthermore, lipidomics analysis is carried out utilizing ultra-high performance liquid-quadrupole-time-of-flight mass spectrometry to identify the obtained lipids. After enzyme treatment, the betaine lipids (BL) content significantly increases, probably due to laccase and cellulase promoting the release of BL from membrane structure. In comparison, the hydrolysis of neutral lipids, glycolipids, and phospholipids during the enzyme treatment reduces their respective contents. The results of this study suggest that using compound enzymes to pretreat N. oceanica can effectively increase lipids extraction yields by ethanol and improve the EPA contents in lipids. Practical applications: This study indicates that enzyme pretreatment can promote the extraction of lipids, especially lipids with EPA, from N. oceanica or other marine microalgae.