Identification of a Novel Feruloyl Esterase by Functional Screening of a Soil Metagenomic Library

A cosmid metagenomic library containing 1.3 × 10⁵ clones was created from a soil sample. A novel gene (fae-xuan) encoding a feruloyl esterase was identified through functional screening. Primary sequence analysis showed that the gene consisted of 759 base pairs and encoded a protein of 252 amino acids. The gene was expressed in Escherichia coli BL21 (DE3) and the corresponding purified recombinant enzyme exhibited a molecular weight of 29 kDa. The FAE-Xuan showed high activity (40.0 U/mg) toward methyl ferulate with an optimal temperature and pH of 30 °C and 5.0, respectively. Besides methyl ferulate, FAE-Xuan can also hydrolyze methyl sinapate and methyl p-coumarate. The substrate utilization preferences and phylogenetic analysis indicated that FAE-Xuan belongs to type A FAE. FAE-Xuan was quite stable over a broad pH range from 3.0 to 10.0. The activity reduced remarkably in presence of Cu²⁺. FAE-Xuan can enhance the quantity of ferulic acid from de-starched wheat bran in presence of xylanase. The work presented here highlighted the effectiveness of metagenomic strategy in identifying novel FAEs with diverse properties for potential use in industrial production.