Photosynthetic bacterial protein production from wastewater: Effects of C/N and light‑oxygen condition

Photosynthetic bacteria (PSB) can produce protein while treating wastewater, thus contributing to sustainable development. This work aims to clarify the effects of wastewater C to N ratio and light‑oxygen condition on protein production performance of PSB. The results showed that PSB could effectively recover protein when C to N ratio was within the range of 5–50 and lower C/N was more favorable. The highest protein productivity in light-anaerobic, dark-aerobic, and light-aerobic condition reached 115.1, 143.4, and 207.7 mg·L−1·d−1, respectively. A light‑oxygen regulation strategy (aerobic conditions should be chosen for wastewater with low C/N, while anaerobic condition should be chosen for wastewater with high C/N) was proposed based on protein productivity. Amino acid composition of PSB could keep stable (essential amino acids: around 40%). This work provides basis for treating wastewater with different C to N ratios and promoting the practical applications of PSB protein recovery technology.