Effects of nitrogen source and nitrogen supply model on the growth and hydrocarbon accumulation of immobilized biofilm cultivation of B. braunii

Abstract

The immobilized biofilm cultivation was a promising method to greatly improve the biomass productivity of microalga Botryococcus braunii, which was considered as an feedstock of renewable biofuel. In this research, the effects of different nitrogen sources and supply methods on growth and hydrocarbon production of B. braunii under immobilized biofilm cultivation (attached cultivation) were studied. Of the total 5 different nitrogen sources, NaNO₃ was selected as the best one with which the high biomass productivity and hydrocarbon productivity of 6.45 gm(-2)d(-1) and 2.79 gm(-2)d(-1) were obtained respectively. The optimized nitrogen concentration was 0.99 mM for non-circulating medium supply model, while for the circulating model, the optimized nitrogen concentration as well as medium volume was 1.49 mM and 1.2L, respectively. Furthermore, nitrogen inputs based on growth of 1 kg dry algae biomass was only 28.92 g with circulating model. Attached cultivation was high efficient in light, nutrient and water utilization.

Keywords: Attached cultivation; Botryococcus braunii; Nitrogen source; Nitrogen supply.