Abstract
Heterotrophic and photomixotrophic cultures of liverwort cells, Marchantia polymorpha, were carried out to investigate growth properties, carbon source utilization and photosynthetic activity of the cells under varied light conditions. The cultures were conducted at incident light intensities of I0 = 0, 30 and 100 W/m2 using an externally illuminated bioreactor containing a medium with 10 kg/m3 glucose as an organic carbon source. At the end of the culture, when glucose in the medium was almost consumed, the amounts of cells harvested were 4.5, 5.5, and 7.0 kg-dry cells/m3 in the cultures at I0 = 0, 30, and 100 W/m2, respectively. The average cell yield based on glucose in the culture at I0 = 100 W/m2 was 0.70, the value of which was 1.6 and 1.3 times as large as those of the cultures at I0 = 0 and 30 W/m2, respectively. In addition, it was estimated that carbon recovery in the cells from glucose ultimately reached 77% in the culture at I0 = 100 W/m2 and this value was the highest in the cultures examined. CO2 fixation and O2 evolution by photosynthesis in M. polymorpha cells were calculated from a stoichiometric equation of cell formation, and correlated with light energy absorbed by the cells in the mixotrophic cultures. It was estimated that the cells possessed photosynthetic ability to fix most of CO2 evolved by respiration over absorbed light energy of about 200 W/kg-dry cells.
