Effects of different photoperiod and trophic conditions on biomass, protein and lipid production by the marine alga Nannochloropsis gaditana at optimal concentration of desalination concentrate

•Optimal 75% DC concentration is appropriate medium for N. gaditana cultivation.•DC provided a higher lipid productivity than the control medium.•The optimal photoperiod cycles for enhancing algal biomass were determined.•The use of the optimum DC medium was evaluated in nine treatments.•Higher SFA production was observed under autotrophic than heterotrophic condition.

This study investigated the cultivation of the marine alga Nannochloropsis gaditana in a medium based on desalination concentrate (DC) with an optimal concentration of 75% DC, under three trophic conditions and four photoperiod schedules. N. gaditana produced a peak biomass concentration (1.25 g L−1) under mixotrophic culture condition and a photoperiod of 16L:08D. N. gaditana cells compensate to different light-dark regimes producing different amounts of protein (17.9-44.8%). The intracellular lipid content in N. gaditana cells increased both under autotrophic conditions with a 16L:08D cycle (16.7%), and under mixotrophic conditions with a 08L:16D cycle (15.7%). In heterotrophic culture, N. gaditana cells were rich in polyunsaturated fatty acids (46.0%). This study demonstrates an alternative approach to enhancing intracellular lipid content of the marine alga N. gaditana by modifying the photoperiod, trophic conditions and stress-salinity-conductivity with the use of a DC-based medium.

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