Discovery and Characterization of Microbial Esterases for Fiber Modification

Carboxyl esterases, particularly arylesterases, were predicted from 16 microbial genomes, and then expressed in E. coli. Of the more than 175 cloned genes, 86 were expressed in soluble form. These were screened for activity using a range of both commercial and natural substrates. Forty-eight proteins were active on pNP-acetate at pH 8 whereas 38 proteins did not exhibit any activity towards any substrates. Among the 48 active proteins, 20 proteins showed arylesterase activity. To date, 8 bacterial esterases and 2 archaeal arylesterases were characterized in terms of pH stability and optima, thermal inactivation, solvent stability, and kinetics. To our knowledge there is only one other published report of arylesterases from archaea. The synthetic capability of arylesterases can transform phenolic acids to value-added chemicals. Accordingly, this project provides an arsenal of industrially significant activities that can extend the antioxidant properties of lignin-derived molecules in a broader range of renewable products.MAS