An acidic feruloyl esterase from the mushroom Lactarius hatsudake: A potential animal feed supplement

An acidic feruloyl esterase (lhFAE) from Lactarius hatsudake was purified to homogeneity, resulting in a high specific activity of 10.3 U/mg toward methyl ferulate as substrate, which was 33.2-fold higher than that of the crude enzyme. lhFAE was a monomeric protein with a molecular mass of 55 kDa. All three internal amino acid sequences exhibited 100% identity with the Laccaria bicolor carbohydrate esterase family 9 protein. The enzyme demonstrated high activity toward methyl ferulate (MFA) at an optimum pH of 4.0 and an optimum temperature at 30 °C, and under these conditions, the Km and Vmax were 0.54 mM and 13.84 U mg−1, respectively. The purified FAE exhibited preference for methyl caffeate over methyl ferulate, and was least active on methyl p-coumarate. Interestingly, above 80% of the enzyme activity was preserved in the presence of metal ions at 5.0 mM concentration, which indicated that lhFAE was highly metal-tolerant. lhFAE was able to release ferulic acid from de-starched wheat bran (DSWB) both in the absence and presence of xylanase, and 70.2% (of the total amount of) ferulic acid (FA) was released by the synergistic action of xylanase. The result showed that lhFAE has good acid and metal ion stability, and is suitable to be used as an animal feed supplement.