The initial phenotypes we have addressed are enzyme thermostability and catalytic turn-over number.  Thermostable pme would be advantageous in the processing of sugar beet pulp in order to take advantage of the energy already invested in heating the pulp to extract sucrose.  We began with native bacterial pmes and performed random mutagenesis on pme genes to generate mutant libraries.  The libraries were screened for thermostability and activity and enzyme variants with desirable characteristics were selected for analysis and further mutation.

We have identified a number of amino acid substitutions that increase pme thermostability and activity.  The mutant enzymes have been characterized for their residual activity after heating and for their kinetic constants.  We are currently characterizing second generation enzymes that have combined several of the mutations identified in the initial selections.