Construction of a bioreactor to produce special breakdown products of phytate.

Escherichia coli phytase was covalently immobilized on NHS-activated Sepharose High Performance. The pH dependence of the phytase activity was not influenced by immobilization, whereas stability against heat treatment was enhanced as a consequence of immobilization. Compared to the free phytase the immobilized enzyme exhibits the same excellent substrate specifity, but showed an increased Km-value. Using the immobilized phytase in a packed-bed bioreactor makes special isomers of the lower myo-inositol phosphate esters available. The major isomers formed were identified as I(1,2,3,4,5)P5, I(2,3,4,5)P4, I(2,4,5)P3 and I(2,5)P2.