Effects of mutual shading, pressurization and oxygen partial pressure on the autotrophical cultivation of Scenedesmus obliquus

The appropriate providing of CO2 and the light energy are known to be detrimental to the growth of photosynthetic cells. In the autotrophical cultivation of Scenedesmus obliquus, the available light intensity drops rapidly due to the effects of mutual shading occurred in the conditions of high cell density. The light penetration ratio promptly decreased to less than 1% at a depth of 1 cm, while the cell density achieved 3 OD. The mutual shading effects seemed severely limiting the maximum cell concentration attained. With the increase of tank pressure higher than 0.5 atm was demonstrated to reversely affect cell growth, which possibly resulted from the inhibition of more dissolved oxygen existing in the medium. The inlet gas with a high oxygen ratio reduced biomass productivity, which was 0.19 g/L/day in the oxygen-enriched batch (98% of pure oxygen supplemental in the inlet gas) as compared to 0.44 g/L/day in the control. These results indicate that both mutual shading and high oxygen partial pressure impede the growth of Scenedesmus in autotrophical cultivation.

► The available light intensity rapidly drops due to mutual shading effects.
► The mutual shading effects seemed severely limiting the maximum cell concentration attained.
► With the increase of tank pressure higher than 0.5 atm was demonstrated to reversely affect cell growth.
► The inlet gas with high oxygen ratio seems to decrease the biomass productivity.