Submitted to: Journal of Industrial Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/10/2011
Publication Date: 6/3/2011
Citation: Wong, D., Chan, V.J., Batt Throne, S.B., Sarath, G., Liao, H. 2011. Engineering Saccharomyces cerevisiae to produce feruloyl esterase for the release of ferulic acid from switchgrass. Journal of Industrial Microbiology and Biotechnology. Epub ahead of print. DOI: 10.1007/s10295-011-0985-9.
Interpretive Summary: The presence of ferulic acid crosslinking the major matrix polysaccharides in plant cell walls has been known to contribute to the recalcitrance of biomass materials. The breakdown of these crosslinks will enhance the digestibility of lignocellulose and enzyme conversion to sugars as feedstock for biofuels and bioproducts. This report describes cloning the gene of a ferulic acid esterase into yeast, resulting in a bioreactor capable of continuous production of the enzyme. This has lead to progressive release of ferulic acid from switchgrass, rendering the cell wall polysaccharides more accessible for complete degradation, as a first step towards combined enzyme conversion/fermentation in a one-pot process.
Technical Abstract: The Aspergillus niger ferulic acid esterase gene (faeA) was cloned into Saccharomyces cerevisiae via a yeast expression vector, resulting in efficient expression and secretion of the enzyme in the medium. The recombinant enzyme was purified to homogeneity by anion-exchange and hydrophobic interaction chromatography. The purified protein had a correct N-terminal sequence of ASTQGISEDLY, indicating that the signal peptide was properly processed. The enzyme had an optimum pH of 6-7 and operated optimally at 50oC using ground switchgrass as the substrate. The yeast clone was demonstrated to catalyze the release of ferulic acid continuously from the switchgrass substrate in culture. This work represent the first report on engineering yeast for the breakdown of ferulic acid crosslinks to facilitate consolidated bioprocessing.