The production of L-malic acid from fumaric acid has been achieved byPichia membraneafaciens cells entrapped in a polyacrylamide gel lattice. The reaction rate was found to be 0.15 mmoles/h/g of immobilized cells. The optimum pH for fumarase activity of immobilized cells was stable after repeated uses it increased after storing the gel pellets at 5°C. A good yield of L-malic acid production (up to 3.77 g/l) was also observed in wine added with Na fumarate.