Lipid dynamics and nutritional value of the estuarine strain Isochrysis galbana VLP grown from hypo to hyper salinity

Novel nutritional/functional applications of Isochrysis strains are mostly based on their diversified lipid classes. The content of these lipids is modulated by different factors, among which salinity has been comparatively understudied. Since managing salinity is key for optimal microalgae outdoor mass production and most studied Isochrysis strains are marine, the lipid response to nearly extreme hypo and hyper salinity in a new estuarine strain is here described. Total lipids in exponentially grown Isochrysis galbana VLP gradually decreased from 334 ± 36.6 mg g -1 at a salinity of 5 psu to 164.3 ± 24.4 mg g -1 at 50 psu. Present is the first report on lipid class (LC) remodeling in response to salinity in any Isochrysis strain. Two main storage lipids, steryl esters (SE) and triacylglycerol (TAG), underwent the fastest absolute decrease as salinity increased during both active and halted growth in the estuarine strain I. galbana VLP. Alkenones also decreased with salinity although less markedly. Among photosynthetic lipids, galactolipids were more affected by salinity than the anionic lipids. Salinity had minor influence on the relative sterol and betaine lipid proportions. Salinity explained more of total LC variation (34.6%) than culture stage (30.3%), whereas the opposite occurred with fatty acid (FA) variation. The main FA affected by salinity were 20:5n-3, 18:3n-3, 18:5n-3 and 18:2n-6. Nutritional value of I. galbana VLP from 5 psu exponential cultures was 1.5-fold to 2-fold higher than under all other conditions. Isochrysis production in low salinity waters can be a sustainable procedure compatible with its optimized nutritional value.