EFFECT OF REDUCING NITROGEN LEVELS ON GROWTH AND LIPID PRODUCTIVITY OF
MICROALGAE BOTRYOCOCCUS BRAUNII EXPOSED BY UV-C RAYS
Thea Prastiwi Soedarmodjo, Arief Widjaja
Departement of Chemical Engineering, Institut Teknologi Sepuluh Nopember, Surabaya 60111, Indonesia
Microalgae Botryococcus braunii is a potential raw material for producing lipids. Mutation using UV-C rays is a method to increase microalgae productivity. Optimum quality of microalgae B.braunii could be achieved by UV-C radiation at 1.5 minutes exposure with a continuous light irradiance cycle. Reduction of nitrogen levels in nutrients and harvesting time were carried out to determine their effect on lipid productivity and lipid content of microalgae B.braunii. Biomass and lipid productivity is largely determined by the growth in the number of cells and cell mass of B.braunii. The highest biomass productivity was produced by native B.braunii in normal nitrogen medium at 7 days of culture. The highest lipid productivity was produced by UV-C mutated B.braunii in low nitrogen medium at 7 days of culture. The highest lipid content was produced by UV-C mutated B.braunii in low nitrogen at 20 days of culture. Native B.braunii provided the highest biomass productivity. The results of Gas Chromatography analysis showed an increase in the content of free fatty acids (FFA) and Monoacylglycerol (MAG) after mutation treatment and culture in low nitrogen medium.
Keywords: Microalgae, Botryococcus braunii, nitrogen limitation, mutation, UV-C.