Impact of Ultraviolet-B Radiation on Growth and Biochemical Composition of Botryococcus braunii Kutz.

The present study examines the impact of ultraviolet-B (UV-B) radiation stress on commercially significant microalga for biofuel application. Experimental alga Botryococcus braunii was treated under different doses of artificially enhanced UV-B radiation. The organism was treated under high dose rates of 1 and 5 Wm(-2) with altered time durations of 15, 30, 45 and 60 min. It showed large variations in the growth characteristics analysed. The rate of whole-cell photosynthetic oxygen evolution showed steep drop in high dose compared to low dose-treated cultures. As a result, level of photosynthetic pigment chlorophyll a content decreased drastically while carotenoid level invariably increased. Consequently, the level of primary metabolites such as total carbohydrate, protein and lipid was drastically reduced under high dose while marginal decrement was observed at lowest dose of UV-B radiation. Overall, the impact of UV-B radiation on B. braunii led to a drop in protective mechanisms with associated decline in growth and cellular imbalance at high intensity studied.