Lipid estimation of different algal species

Abstract

In the present investigation eight different microalgae were screened for growth and lipid content grown under both indoor and outdoor conditions. Three heterocystous, filamentous cyanobacteria Nostoc muscorum (ARM 442), Anabaena variabilis (ARM 441), Tolypothrix tenuis (ARM 443) were selected along with Spirulina sp. and other microalgae such as Nannochloropsis oculata, Botryococcus braunii, Scenedesmus armatus and Isolate no. 5 (PS 1). To maximise lipid extraction, the algal cells were homogenised and ultrasonicated. Overall it was observed that all the algal cultures showed increase in biomass and lipid content with increase in time interval of 7 days respectively. Nostoc muscorum (ARM 442) showed highest lipid content 0.47 mg/ml with increase in wet biomass from 0.16 mg/ml as observed on 0 day to 0.43 mg/ml on 28th day and increase of dry biomass from 0.03 mg/ml on 0 day to 0.15 mg/ml on 28th day under lab conditions respectively, whereas lipid content in Spirulina sp. when cultivated under open conditions, showed increase in lipid content from 0.02 mg/ml on 0 day to 0.17 mg/ml on 28th day in 0.1 ml organic layer, 0.05 mg/ml on 0 day to 0.35 mg/ml on 28th day , 0.12 mg/ml on 0 day to 0.57 on 28th day, with the increase in wet biomass from 0.23mg/ml on 0 day to 0.55 mg/ml on 28th day and dry biomass from 0.05 mg/ml on 0 day to 0.19 mg/ml on 28th day respectively. Overall chlorophyll content in both open and closed conditions was observed to be maximum in Spirulina sp. by (0.5µg/ml) in open and (1.47 µg/ml) in closed conditions. Microalgae were disrupted by homogenization and ultrasonication to release lipids. Maximum lipids were released when cells were homogenized and further ultrasonicated. In situ tranesterification was done for making biodiesel. Spirulina sp. (0.4 mg/ml) appeared to be potential source for biodiesel production followed by Nannochloropsis oculata (0.4 mg/ml) and Botryococcus braunii (0.24 mg/ml) as they contain high lipid content and grow rapidly in indoor and outdoor conditions.