Expression, purification and characterization of a feruloyl esterase A from Aspergillus flavus

Feruloyl esterases are key enzymes involved in the complete hydrolysis of hemicellulose. In the present study, the encoding sequence of putative feruloyl esterase A (AfFaeA) was cloned from genomic DNA from Aspergillus flavus and expressed in Pichia pastoris. The purified recombinant AfFaeA had apparent relative molecular mass of about 40,000 and had an optimum pH of 6.0, although it was stable at pH values ranging from 4.5 to 8.0. The optimum temperature for AfFaeA was 58°C. AfFaeA had hydrolytic activity toward methyl caffeate, methyl p-coumarate, methyl ferulate and methyl sinapate. Substrate specificity profiling of AfFaeA demostrated it is a type-A feruloyl esterase. The good performance of AfFaeA to release ferulic acid from steam exploded corn stalk in concert with Geobacillus stearothermophilus xylanase mutant indicated it is a promising biocatalyst for biomass degradation.