For all experiments, the bioreactors were the 500 mL conical flasks, which were sterilized at 121 C for 30 min before experiments. During the experiment, 200 mL anaerobically digested swine wastewater was added to the bioreactor each time after sterilization by autoclave.
All the experiments were undertaken in a constant temperature (30 C) illumination incubator, the parallel fluorescent bulbs positioned on the side of flasks acted as the light source, and the intensity of illumination at the surface of the bottles were about 3000 lx for wastewater treatment. These stock culture were inoculated to anaerobically digested swine wastewater at a volume ratio of 1:10 except for where it was noted.