Growth rate assessment of high lipid producing microalga Botryococcus braunii in different culture media

Abstract

The green colonial microalga, Botryococcus braunii is well known for its high lipid content and has already been proposed as a renewable energy source for various aquaculture and biotechnological applications. However, due to its slow growth rate compared with other microalgae, B. braunii has not yet been used in mass culture to produce more biomass. Therefore, in this study we tested different culture media to enhance the growth rate of B. braunii. B. braunii samples were collected from natural habitat, isolated and purified by repeated streaking on agar plate. The purified samples were cultured in six treatments containing different culture media with incubation conditions of pH 7.5, temperature 25±1°C under 1.2±0.2 klux light intensity with 12 hr photoperiod to observe their growth rate and morphology. The results of this study showed the highest growth rate (µ=0.20 day-1) in the autoclaved lake water with 427 colonies/ml. Bold’s basal medium (BBM) and modified Chu No. 10 medium showed moderate growth after 24 days of incubation. The growth rates amongst all media were significantly different (p < 0.05) except between un-autoclaved lake water and autoclaved water medium added with half concentration of BBM. Morphological observation showed that B. braunii varied in different culture media. This study illustrated that autoclaved lake water has the highest growth rate compared to formulated media such as BBM and modified Chu No. 10 medium. This indicates that the autoclaved lake water medium had high concentration of nutrients and can be used for the mass production of B. braunii at lower cost.