Heterotrophic nitrification and aerobic denitrification by Diaphorobacter polyhydroxybutyrativorans SL-205 using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) as the sole carbon source

Abstract

A new strain of Diaphorobacter polyhydroxybutyrativorans (strain SL-205) was recently isolated and identified. SL-205 can utilize nitrate and nitrite for denitrification and ammonium for nitrification using poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) as the carbon source under aerobic conditions. SL-205 removed 99.11% of NH₄⁺-derived N (83.90mg/L), 95.02% of NO₃^--N (308.24mg/L), and 84.13% of NO₂^--N (211.70mg/L), with average removal rates of 1.73mg NH₄⁺-N/(L·h), 6.10mg NO₃^--N/(L·h), and 4.95mg NO₂^--N/(L·h). Nitrogen gas was the primary end-product, with negligible nitrous oxide accumulation during ammonium removal, accounting for 57.85% of the removed NH₄⁺-N and 52.30% of the initial NH₄⁺-N. Moreover, hydroxylamine oxidoreductase, nitrate reductase, and nitrite reductase were detected, further indicating that strain SL-205 underwent heterotrophic nitrification coupled with aerobic denitrification (NH₄⁺→NH₂OH→NO₂^-→NO₃^-→NO₂^-→N₂O→N₂). These results support the use of PHBV as a carbon source for nitrogen removal from water and wastewater by strain SL-205.

Keywords: Aerobic denitrification; Carbon source; Diaphorobacter polyhydroxybutyrativorans; Heterotrophic nitrification; Poly(3-hydroxybutyrate-co-3-hydroxyvalerate).