Patent ID: 7504207

Claim:
A method for producing mutant genes encoding an enzyme, comprising: (a) introducing mutations into individual copies of a gene to form a plurality of mutated genes, wherein each mutated gene encodes a mutated enzyme; (b) providing the mutated genes to host bacteria by inserting the mutated genes into vectors and transforming the bacteria with the vectors; (c) culturing the host bacteria containing the vectors in the presence of a substrate for the enzyme under conditions suitable for activity of the enzyme such that a bacterium expressing a functional enzyme from a mutated gene has a detectable characteristic; (d) sorting host bacteria having the detectable characteristic by flow cytometry, wherein the host bacteria are sorted without selecting for an altered or defined level of enzyme activity compared with a corresponding wild type enzyme; and (e) obtaining a pool of mutated genes encoding functional enzymes from the bacteria in step (d) and repeating steps (a) to (d) to form a library of bacteria containing a plurality of mutant genes expressing a functional enzyme.