DNA shuffling was used to make a double mutant lactate oxidase (E160G/V198I LOD) in E. coli was more thermostable than both E160G single-mutant and wild-type LODs. The half-life of this E160G/V198I LOD at 70 degrees C was about 3 times that of E160G LOD, and was about 20 times that of wild-type. In contrast, the thermostability of the V198I single-mutant LOD made by site-directed mutagenesis was almost identical to that of wild-type. This indicates that the V198I mutation alone does not affect LOD thermostability but does affect it when combined with the E160G mutation.