Molecular cloning, expression and characterization of a novel feruloyl esterase from a soil metagenomic library with phthalate-degrading activity

Objectives To discover novel feruloyl esterases (FAEs) by the function-driven screening procedure from soil metagenome. Results A novel FAE gene bds 4 was isolated from a soil metagenomic library and over-expressed in Escherichia coli. The recombinant enzyme BDS4 was purified to homogeneity with a predicted molecular weight of 38.8 kDa. BDS4 exhibited strong activity (57.05 U/mg) toward methyl ferulate under the optimum pH and temperature of 8.0 and 37°C. Based on its amino acid sequence and model substrates specificity, BDS4 was classified as a type-C FAE. The quantity of the releasing ferulic acid can be enhanced significantly in the presence of xylanase compared with BDS4 alone from de-starched wheat bran. In addition, BDS4 can also hydrolyze several phthalates such as diethyl phthalate, dimethyl phthalate and dibutyl phthalate. Conclusion The current investigation discovered a novel FAE with phthalate-degrading activity and highlighted the usefulness of metagenomic approaches as a powerful tool for discovery of novel FAEs.