Effect of cobalt enrichment on growth and hydrocarbon accumulation of Botryococcus braunii with immobilized biofilm attached cultivation

•Botryococcus survived high cobalt concentration of 4.5 mg L−1.•Hydrocarbon and its long chain component were increased under cobalt enrichment.•Attached cultivation of B. braunii might be high efficient in cobalt removal.

The effects of cobalt enrichment on the growth and hydrocarbon accumulation were studied with biofilm attached cultivation. Under biofilm attached cultivation conditions, the microalga Botryococcus braunii survived high concentration of cobalt (50× normal level). The crude hydrocarbon content as well as the long C chain component (C31) increased under Co enrichment treatment indicating the activity of key enzyme that catalyze hydrocarbon synthesis might be enhanced by Co enrichment. The reduced carbohydrate and protein contents accompanied by increased hydrocarbon content for Co enrichment treatment indicating the Co was also an effective factor that controls the carbon flow of B. braunii. Under Co enrichment treatment, totally 1473.9 μmol of Co element was consumed to produce one gram of algal biomass, indicating this attached cultivation method is high efficient in heavy metal elements removal.