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.