Strategies for lignocellulosic hydroxycinnamic acid release and biotransformation into high-value coniferyl alcohol...

The increasing need for sustainable strategies to valorize lignocellulosic biomass has driven significant advancements in enzymatic and biocatalytic methodologies. This chapter presents an integrated, scalable approach for the release and biotransformation of hydroxycinnamic acids (HCADs), such as ferulic acid (FA) and p-coumaric acid (pCA), into high-value coniferyl alcohol (COL). Utilizing XynZ, a chimeric enzyme with feruloyl esterase and xylanase activities, this method enables efficient hemicellulose degradation and HCAD release. Whole-cell biocatalysis, employing recombinant Escherichia coli co-expressing carboxylic acid reductase (CAR) and aldo-keto reductase (AKR), facilitates the direct biotransformation of HCADs into COL in a streamlined process. A fed-batch strategy further enhanced COL production, achieving up to 1.6 g/L titers. Including alkaline hydrolysis protocols demonstrates a robust alternative for HCAD recovery, offering higher yields than enzymatic methods. This work bridges key gaps in lignocellulosic biomass valorization, providing a state-of-the-art, sustainable, and industrially relevant platform for converting agro-industrial residues into high-value phenolic compounds. The methodologies outlined align with green chemistry principles and address critical challenges, advancing the development of economically viable biorefineries.