This work investigated the effects of eight metal ions on Rhodopseudomonas palustris growth and 5-aminolevulinic acid (ALA) yield in wastewater treatment. Results show that metal ions (Mg2+ of 15 mmol/L, Fe2+ of 400 μmol/L, Co2+ of 4 μmol/L, Ni2+ of 8 μmol/L and Zn2+ of 4 μmol/L) could effectively improve the chemical oxygen demand (COD) removal, Rp. palustris biomass and ALA yield. The highest ALA yield of 13.1 mg/g-biomass was achieved with Fe2+ of 400 μmol/L. ALA yields were differentially increased under different metal ions in the following order: Fe2+ group > Mg2+ group > Co2+ group = Ni2+ group > Zn2+ group = Mo2+ group > control. Cu2+ and Mn2+ inhibited Rp. palustris growth and ALA production. Mechanism analysis revealed that metal ions changed ALA yields by influencing the activities of ALA synthetase and ALA dehydratase.

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