Effect of different concentrations of gibberellins on antibiotics and nutrient removal using microalgae-bacteria consortia system

Phytohormone gibberellins (GAs) were utilized to enhance the removal of tetracycline antibiotics and nutrients from swine wastewater by different algal-bacterial symbiosis. Compared to microalgae monoculture, microalgae-activated sludge, and microalgae-Bacillus licheniformis, microalgae-endophytic bacteria showed better growth, photosynthetic, and purification performance. At 50 mg L−1 GAs addition concentration, the specific growth rate of Chlorella vulgaris-endophytic bacterial (S395-2) system was 0.331 ± 0.03 d−1, the maximum removal rate of tetracycline (TC), total nitrogen (TN) and total phosphorus (TP) was 96.31 ± 2.73%, 86.37 ± 8.31% and 87.26 ± 8.42%, respectively. The purification effect was much higher than the level of microalgae monoculture without GAs addition (TC removal of 81.33 ± 7.71%, TN and TP removal of 62.51 ± 5.95% and 64.25 ± 6.13%, respectively). In summary, exogenous GAs simultaneously promoted the resistance and biomass accumulation of algal symbiosis, which supplied a theoretical foundation for the treatment of high-concentration nutrients and antibiotics wastewater.