Fe2+ enhancing biomass production and soybean wastewater treatment of photosynthetic bacteria through regulation of aerobic respiration

Abstract

Wastewater purification and biomass resources recycling can realized by photosynthetic bacteria (PSB) simultaneously. However, the low biomass production limits PSB biomass recycling productiveness in wastewater treatment. This paper studied the iron ions enhancement of PSB biomass production through regulating the aerobic respiration. Results showed that COD removal (95%) was the best; the hydraulic retention time was cut 24 h at 20 mg/L Fe 2 + dosage. Up to 5000 mg/L biomass production at 20 mg/L Fe 2 + dosage was obtained and was 1.5 times for control group. Theoretical analysis stated clearly the potential reason was that Fe 2 + composed the iron–sulfur clusters of dehydrogenases active center. Thus, energy production was raised by Fe 2＋ of up-adjusting the activity of dehydrogenase. Accumulation of PSB biomass needed a lot of energy. The NADH dehydrogenase and succinate activities were raised by 50%, 40.6% respectively under 20 mg/L dosage. And 39.4% increase in energy (ATP) was obtained. Furthermore, we proposed another mechanism: Fe 2 + could control the succinate and NADH dehydrogenase activities through inducing the expression of iron–sulfur cluster assembly operon. • Optimal 20 mg/L Fe 2＋ enhanced biomass production and reduced hydraulic retention time. • Fe 2＋ could improve the efficiency of biomass recycling in PSB wastewater treatment. • New mechanism for Fe regulating aerobic respiration to produce energy was proposed.