Efficient production of thermostable Thermus thermophilus xylose isomerase in Escherichia coli and Bacillus brevis.

The xylose (glucose) isomerase from the thermophile Thermus thermophilus seems to have potential for the development of new isomerization processes using high temperatures and slightly acidic pH. The isomerase has an optimum temperature at 95 degrees C, and is also very stable at high temperatures. The optimum pH is around 7.0, close to where by-product formation is minimal. Since Thermus produces only a little of this useful isomerase, the production of the cloned gene in Escherichia coli and Bacillus brevis were compared. Especially B. brevis was able to produce the isomerase efficiently, more than 1 g/l, in spite of the high G + C content (67%) of the Thermus gene, and the presence of codons not frequently used in E. coli or B. brevis.