Effects of nutrient levels on cell growth and secondary carotenoids formation in the freshwater green alga, Chlorococcum sp.

The freshwater green alga Chlorococcum sp. grew on NH4+, NO3-, urea, yeast extract, and peptone as the nitrogen source showing similar patterns of growth and secondary carotenoid (SC) production. However, the most suitable nitrogen source for the induction of SC was urea. The effects of nutrient levels (urea, phosphate, sulfate, ferrous iron, and salt) on growth and SC production were studied by varying the concentration of each nutrient in batch cultures. High biomass production was achieved in cultures containing 20-28 mM urea, 4.8-10 mM phosphate, 1.6 mM sulfate, 70 mM NaCl, and 20-100 mu M iron. The highest SC content in biomass was obtained when cultured at 5-10 mM urea, 1-2 mM phosphate, 1.6 mM sulfate, 170 mM NaCl, and 50 mu M iron. The optimum concentrations of nutrients for biomass and for the SC accumulation in biomass were evaluated and the two media for achieving high biomass production and SC production were thus developed. The extent to which each parameter to stimulate the formation of SC in the alga were varied and the potentially improved SC production by manipulating the nutrient levels in the modified media were discussed.