The feruloyl esterase system of Talaromyces stipitatus: production of three discrete feruloyl esterases, including a novel enzyme, TsFaeC, with a broad substrate specificity

Abstract

Several extracellular feruloyl esterases were produced by the mesophilic fungus Talaromyces stipitatus when grown on selective carbon sources in liquid media. Type-A and Type-B feruloyl esterases, as defined by their substrate specificity against methyl hydroxycinnamates, were produced during growth on wheat bran and sugar beet pulp, respectively. In addition, Tal. stipitatus produced a new type of esterase (TsFaeC) during growth on sugar beet pulp with a broader spectrum of activity (Type-C) against the (hydroxy)cinnamate esters than those previously described. All three enzymes were purified and N-terminal amino acid sequences and internal peptide sequences determined. The TsFaeC sequences were used to amplify a gene fragment from Tal. stipitatus genomic DNA. The flanking sequences were identified with the aid of RACE-RTPCR, and a full-length clone constructed. The faeC gene is present as a single copy and contains a single intron. The complete cDNA fragment contains an ORF of 1590 bp, faeC, which is predicted to encode a 530 amino acid pre-protein, including a 25-residue signal peptide, and to produce a mature protein of M R 55 340 Da. There was no evidence for a carbohydrate-binding domain in TsFaeC.