Involved in the recovery of exogenous heme iron. Extracts iron from heme while preserving the protoporphyrin ring intact. 2 H(+) + heme b = Fe(2+) + protoporphyrin IX Binds 1 heme b (iron(II)-protoporphyrin IX) group non-covalently per subunit. Homodimer. Part of a ferrous iron transporter composed of EfeU, EfeO and EfeB (By similarity). Predicted to be exported by the Tat system. The position of the signal peptide cleavage has not been experimentally proven. Belongs to the DyP-type peroxidase family. EfeB subfamily.