Cultivation of Botryococcus braunii has been mainly reported in photoautotrophicmodewhich
has some disadvantages such as low cell growth rate and low cell density. For high density
and high productivity, this study attempts to cultivate B. braunii in mixotrophic mode. Effects
of different organic carbon sources (including maltose, glucose, saccharose, lactose, glycerol
and starch), glucose andKNO3 concentrations as well as inoculation amount on the growth of
B. braunii were investigated in 250 mL shake flasks, and a fed-batch mixotrophic cultivation
technique was developed in a 10 L enclosed automatic air-lift photobioreactor.
B. braunii grew faster in mixotrophic cultivation with all the six organic carbon sources
than that in photoautotrophic mode, and glucose was the optimum. The optimal
concentrations of glucose and KNO3 were 2.5 g L1 and 0.4 g L1 respectively. Within the
inoculums of 46e200 g m3, the lag phase of cell growth was very short, and cells grew fast
into exponential phase after inoculation, the average cell growth rate of B. braunii increased
with the increment of inoculation amount. With a 10 L air-lift photobioreactor, B. braunii
was cultured by feeding glucose under mixotrophic condition for 19 days, and the cell
density and hydrocarbon content in dry cell reached 4.55 g L1 and 29.7%, respectively