Feruloyl esterases acting on plant cell wall polymers represent key tools for degradation of plant cell wall. It represents a diverse group of hydrolases catalyzing the cleavage and formation of ester bonds between plant cell wall polysaccharide and phenolic acid. They are widely distributed in plants and microorganisms. The work in this book describes(1) Literature studies on feruloyl esterases.(2) Production, partial purification and characterization of feruloyl esterase (FAE-II) by Aspergillus awamori in submerged fermentation.(3) Studies on temperature dependent kinetics of native Aspergillus awamori feruloyl esterase FAE-II in water solutions.(4) Biochemical studies on native and cross-linked aggregates of Aspergillus awamori feruloyl esterase(5) Stability and solubility studies of native and activated Aspergillus awamori feruloyl esterase(6) Expression of feruloyl esterase from Aspergillus awamori in Escherichia coli; Characterization and crystal studies of the recombinant enzyme.