Novel Ferulic Acid Esterase From Human Gut Microbiome: Cloning and Application in Crop Residue Valorization

Ferulic acid esterases (FAEs) are enzymes that interact with esterified components of plant cell walls, facilitating the release of free ferulic acid (FA) from plant materials. Therefore, they hold significant importance across multiple industries, including pharma, food, and cosmetics. This investigation involved the cloning, expression, and characterization of FAE from the human fecal metagenome. Sequence analysis revealed that the cloned gene was approximately 750 bp in length and contained an open reading frame encoding a protein of 252 amino acids. The resulting recombinant protein displayed a molecular weight of 28 kDa and 49.7% identity with the chlorogenic acid esterase from Lactobacillus helveticus. The hydrolytic activity of the recombinant FAE was validated using p-nitrophenyl-ferulate (pNPF) as the substrate, with optimal activity at a pH of 7 and a temperature of 35°C. The enzyme showed stability within a pH range of 5.0-7.0 and temperatures from 5°C to 35°C. High-performance liquid chromatography (HPLC) results indicated that the FAE enzyme could release up to 49.7% of total alkali-extractable FA from dehydrated rice bran, followed by wheat bran and sugarcane bagasse. The total phenolic content of sugarcane bagasse increased by approximately 100% after in situ enzymatic fermentation compared with the chemically extracted fraction. These results indicate that cloned FAE can be used as a potential biocatalyst in industrial applications.