Biomass production and variation in the biochemical profile (total protein, carbohydrates, RNA, lipids and fatty acids) of seven species of marine microalgae

Abstract

Seven species of marine microalgae ( Pavlova lutheri, Isochrysis galbana, Tetraselmis suecica, Chaetoceros calcitrans, Phaeodactylum tricornutum, Rhodomonas sp. and Heterosigma akashiwo) were harvested at three phases in the growth curve and biochemical composition (total protein, carbohydrates, RNA, lipids and fatty acids) was determined. Carbohydrate and lipid contents increased with the development of the culture, while protein levels increased in the later phases of the culture in the case of diatoms and Rhodomonas sp. and decreased in I. galbana, P. lutheri and T. suecica. Saturated fatty acids and, to a lesser extent, monoethylenic fatty acids represent between 70 and 100% of the total fatty acids. Polyunsaturated fatty acids reached their highest values in the exponential phase in Rhodomonas sp. (30.99%), in an early stationary phase in P. tricornutum (19.58%) and C. calcitrans (9.06%) and in a late stationary phase in I. galbana (12.89%), P. lutheri (4.24%) and T. suecica (18.58%). RNA levels never exceeded 2.5%. The daily production was calculated for each batch culture in three growth phases and was compared with the production of a semicontinuous culture maintained in the exponential phase. Rhodomonas sp., C. calcitrans and P. tricornutum showed a lower daily production under semicontinuous culture than in batch cultures, while I. galbana, P. lutheri, T. suecica and H. akashiwo showed the opposite. The daily production of each of the biochemical components also varied with the species.