Long-term semi-continuous cultivation of a halo-tolerant Tetraselmis sp. using recycled growth media.

Graphical abstract Highlights • Tetraselmis sp. could grow in extreme Qatar climate condition throughout the year. • The annual average biomass productivity of Tetraselmis sp. was 17.81 g/m2/d. • Recycling growth media had no effect on the biomass productivity of Tetraselmis sp. • Iron content in ferric chloride assisted harvested Tetraselmis biomass was 1.5–3.3%. • Acid solution could leach >91% iron from freshly harvested Tetraselmis biomass. Abstract In this study, a halotolerant Tetraselmis sp. was selected for 11-month outdoor semi-continuous cultivation in one sq. m raceway tank in the Qatari desert. A fraction of the culture was harvested using ferric chloride, and the growth media was returned to the tank. The recycling of culture media continued till the culture salinity reached 8% NaCl; 90% culture was then harvested, and the remaining culture fraction was used as inoculum for a new cultivation cycle. The growth of Tetraselmis sp. was not affected by incremental salinity although the intracellular metabolites varied; the average biomass productivity was 17.8 g/m2/d. Harvesting efficiency was slightly affected by the increase in salinity. Iron content in the harvested biomass was in the range of 1.5–3.3%, and acidic solution (pH = 1.48) was able to recover 91.3% iron from the harvested biomass. Nonetheless, Tetraselmis sp. could be grown continuously throughout the year in Qatar's climate condition. [ABSTRACT FROM AUTHOR]