Single and co-cultivation of Chlorella vulgaris and Pseudomonas aeruginosa: Efficient nutrient removal and lipid/starch formation by photoperiodic co-culture

Co-cultivation of Chlorella vulgaris and Pseudomonas aeruginosa was investigated, aiming at enhanced nutrient removal and storage material formation. The effect of the initial level of C-source (glucose), inoculum percentage of bacteria (0–100) and trophic conditions (hetero- and mixo-) was investigated, resulting in selection of 2 g/L glucose and 50 % bacteria in inoculum under mixotrophic condition. This led to the highest nutrient removal (43.6 % nitrate, 96.7 % glucose and 99.5 % phosphate) and improved cell contents of lipid (20.8 %) and starch (10.9 %), surpassing those of single microalgal culture. Additionally, six photoperiodic co-cultivations with a preparatory heterotrophic condition (48 h), followed by mixotrophic conditions (continuous and cyclic lighting), were applied at three initial nitrate levels (1200, 800, and 400 mg/L). Continuous lighting and nitrate at 400 mg/L led to complete nutrient removal and the highest lipid (633.8 mg/L) and starch (493.9 mg/L) production. These results validate the potential of photoperiodic co-cultures of bacteria and microalgae for wastewater treatment alongside lipid and starch production, which can serve as valuable biofuel resources.