A 4-hydroxy-3-methoxycinnamic acid (ferulic acid) esterase has been purified from the extracellular broth of cultures of Streptomyces olivochromogenes after growth on oat spelt xylan. The purification procedure utilizes ion exchange on DEAE-BioGel A, anion exchange on Mono Q, gel filtration and hydrophobic interaction chromatography. The purified enzyme appeared as a single band on SDS-PAGE, with an apparent M(r) of 29000. Two bands, at pI 7.9 and 8.5, were observed on isoelectric focusing. With methyl ferulate as substrate, the pH and temperature optima were 5.5 and 30°C respectively, with a K(m) of 1.86 mM and V(maX) of 0.3 μmol min-1 mg-1. The purified enzyme released ferulic acid from de-starched wheat bran only in the presence of xylanase.