Enhancing the omega-3 fatty acid synthesis of marine microalgae using indigenous red seaweed resources of Gulf of mannar region as liquid fertilizers

Fatty acids of microalgae particularly EPA and DHA has great attention worldwide in recent times due its major role in human neurological development and microalgae is considered to be a best source. Hence, the present study was aimed to utilize indigenous seaweeds as a bio-stimulant in enhancing the fatty acid synthesis of microalgae. Three different seaweed liquid fertilizers (SLFs) prepared from indigenous seaweed species viz., Gracilaria edulis (SLF-1), Gelidiella pannosa (SLF-2) and Sargassum wightii (SLF-3) contain enormous amount of essential nutrients required for microalgal growth. Nitrogen, potassium and iron levels were higher in SLF-1 whereas phosphorous, calcium and zinc levels were higher in SLF-2. The growth performance of both alga on three different SLFs revealed that the SLFs prepared from the red seaweed was highly efficient than the brown seaweed. Both the red SLFs significantly enhanced the growth performance, physiological and biochemical response of microalgae. In addition, SLFs had enhanced the EPA and palmitoleic acid concentration in N. oculata and D. salina respectively. SLFs 1 and 2 enhanced the EPA content of N. oculata by 19.85% and 6.35% whereas in D. salina the palmitoleic acid concentration was increased by 18.07% and 21.43% respectively. DHA was detected only in the microalgae cultured using SLFS but at trace levels of 0.01-0.02%. These study results suggest the potential application of seaweeds as cost effective culture media for microalga with an added advantage of enhancing its nutritional properties.