Sunday, April 29, 2007
2-65

Characteristics of two ferulic acid esterases from Penicillium funiculosum

Eric P. Knoshaug, Michael J. Selig, Stephen R. Decker, Michael E. Himmel, and William S. Adney. National Renewable Energy Laboratory, 1617 Cole Blvd MS 3323, Golden, CO 80401

Diferulate esters serve to cross-link hemicelluloses and lignin in plant cell walls and may contribute to the natural recalcitrance of biomass to microbial degradation. Microbial ferulic acid esterases (EC- No. 3.1.1.73) are generally secreted and catalyze the hydrolysis of ester and ether bridges between hydroxycinnamic acids and polysaccharides and/or lignins in plant cell walls. We evaluated the biochemical characteristics of two heterologously expressed ferulic acid esterases and their potential to increase the digestibility of pretreated biomass. Two ferulic acid esterase genes, faeA and faeB, were PCR cloned from Penicillium funiculosum ATCC62998 and expressed in Aspergillus awamori using their native signal sequence. Both enzymes contain a catalytic domain that is connected to a Family one carbohydrate binding module by way of a threonine-rich linker peptide. Interestingly, they differ in that the CBM is N-terminal in faeA and C-terminal in faeB. The enzymes were purified to homogeneity and thermal stability was characterized by circular dichroism and differential scanning microcalorimetry. We evaluated both enzymes for their potential to enhance activity of purified Trichoderma reesei Cel7a on pretreated corn stover and what role, if any, the CBM of these enzymes play in that enhancement.

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