Comparison of Chlorella vulgaris biomass productivity cultivated in biofilm and suspension from the aspect of light transmission and microalgae affinity to carbon dioxide

Abstract

To investigate light transmission and cells affinity to CO₂, Chlorellavulgaris was attached to microfiltration membrane that laid on the solidified BG11 medium compared to that in suspended cultivation mode in this study. The results showed that C. vulgaris showed a 30.4% higher biomass production (103gm^-2) in attached than in suspend system. The upper layer of biofilm with a thickness of 41.31μm (the corresponding areal density of 40gm^-2) was effectively illuminated under light intensity of 120μmolm^-2s^-1 and more than 40% of the microalgal cells were in light even the areal density was high to 100gm^-2. While only 2.5% of the cells were effectively illuminated in the suspended cultivation system. Furthermore, microalgae cells in biofilm showed a higher affinity to CO₂ compared with that in suspension, and CO₂ saturation point of microalgae cells in biofilm was 1.5% but 4.5% in suspension.

Keywords: Affinity to CO(2); Attached cultivation; Biofilm; Light penetration; Microalgae.