The enzyme mannose isomerase (EC 5.3.1.7) catalyzes the isomerization of D-mannose and D-fructose. The conversion of mannose to fructose is the first step in the principal pathway of mannose dissimilation by Pseudomonas cepacia. This enzyme is induced during growth on medium containing mannose to levels three- to four-fold higher than observed during growth on glucose or citrate. Mannose isomerase was purified from extracts of mannose-grown P. cepacia and was efficiently immobilized onto a porous, noncompressible, ceramic support. The performance of the immobilized enzyme, compared with the soluble enzyme, was evaluated under a variety of operating conditions to examine its potential for use in a process for the production of fructose syrups containing a higher proportion of fructose than is currently possible using glucose isomerase.