Chitosan-coated oleaginous microalgae-fungal pellets for improved bioremediation of non-sterile secondary effluent and application in carbon dioxide sequestration in bubble column photobioreactors.

Oleaginous microalga Scenedesmus sp. SPP was rapidly immobilized in oleaginous fungal pellets by their opposite-surface-charges. Microalgae-fungal (MF) pellets were more effective in bioremediation of non-sterile secondary effluent than mono-culture. The optimal hydraulic retention time for dual bioremediation in semi-continuous mode was 72 h. The MF pellets coated with 0.4 %-chitosan improved removal efficiencies of COD, total nitrogen (TN), and total phosphorus (TP) up to 96.2±0.0 %, 88.2±2.8 % and 71.5±0.7 %, respectively, likely because of better cell retention and more nutrient adsorption and assimilation. Dual bioremediation by coated MF pellets was also successfully scaled up in 30-L bubble-column photobioreactors with improved COD, TN, and TP removal efficiencies of 98.5±0.0 %, 90.2±0.0 % and 79.5±2.1 %, respectively. This system also effectively removed CO from simulated flue gas at 71.2±0.4 % and produced biomass with high lipid content. These results highlight the effectiveness of bio-immobilization by fungal pellets; chitosan coating; and their practical applications in bioremediation and CO sequestration.