Immobilization of Proteus vulgaris for the reduction of 2-oxo acids with hydrogen gas or formate to d-2-hydroxy acids

For the stereoselective reduction of 2-oxo acids by hydrogen gas or formate to d-2-hydroxy acids, anaerobically grown Proteus vulgaris cells were immobilized in alginate, -carrageenan, chitosan, polyurethane and polyacrylamide acylhydrazide. With the exception of the last matrix, immobilization led to a decrease in the apparent activity, probably caused by diffusional limitations. Chitosan or polyurethane-entrapped cells kept their initial catalytic activity for over more than 600 h in a continuous working period. In both matrices the cells could be partially reactivated by incubation of the immobilisates in growth medium. Polyurethane-immobilized cells (and also cell membranes) were repeatedly usable. After 30 batch operations, 30–40% of the initial reduction rate was still detectable. Chitosan-immobilized cells did not lose any activity during 17 months of storage at 4° C under exclusion of oxygen. Correspondence to: H. Simon