Isolation, characterization and outdoor cultivation of green microalgae Botryococcus sp.

Samples of the green, colonial, unicellular microalgae Botryococcus sp. were collected from freshwater ponds in Mahabalipuram, Tamil Nadu, India. Specimens were isolated and examined for morphological features using microscopic and scanning electron microscopic images and was found to be Botryococcus sp. The hydrocarbon analysis of its hexane extracts showed hexadecane (10.15%), heptadecane (17.82%) and pentacosane (18.74%) as its major hydrocarbons. Further, the 18S rRNA sequence (GU182893.1) analysis has confirmed its taxonomical relationship to the order Trebouxiophyceae and has shown similarities with the reported species of the genus Botryococcus and in particular to Botryococcus braunii. Based on morphological features and 18S rRNA sequence analysis, the Indian isolate was designated as Botryococcus mahabali. Biomass analysis of B. mahabali showed 19% proteins, 18% carbohydrates and 14% lipid. It was found that its oil comprised mainly of hexadecadienoic acid (16:2), oleic (18:1), linoleic (18:2), and linolenic acids (18:3) as its major fatty acids. Oleic acid is recognized to be the major fatty acid in most of the reported species of the genus Botryococcus and thus it can serve as another significant chemical signature for the Indian isolate. Its pigment profile exhibited lutein (41.57%) and �-carotene (37.96%) as major carotenoids. In view of its chemical profile, the algae was scaled up in open air raceway ponds in batch mode and the biomass yields were found to be 2 g/L (w/w) up on two weeks growth in outdoor raceway ponds. In conclusion, the results of the study reveal that an Indian isolate B. mahabali can be of relevance for its prospective applications from food to biodiesel feed stock.

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