Improvement of production rate and yield of fumaric acid from maleic acid by heat treatment of Pseudomonas alcaligenes strain XD-1

Abstract In order to increase the production yield of fumaric acid from maleic acid by Pseudomonas alcaligenes strain XD-1, we investigated the selective thermal inactivation of fumarase, which converts fumaric acid to l -malic acid. The addition of calcium ions was effective in increasing the thermal resistance of maleate cis – trans isomerase, although the isomerase showed higher stability than the fumarase even in the absence of calcium ions. When the cells were heated in the presence of 30 mM CaCl 2 at 70 °C for 1 h, almost all fumarase was inactivated, while the maleate cis – trans isomerase remained active. The heat-treated cells showed a higher production rate of fumaric acid than that of the untreated cells. It was discussed in relation to the change of the cell membrane properties by the heat treatment, allowing easier mass transfer through it. As a result, the heat-treated cells produced fumaric acid of 57.0 g/l from maleic acid of 60 g/l in a reaction period of 4 h. The production yield of fumaric acid on the basis of the amount of substrate supplied was improved to 95.0% from the value of 69.8% obtained by the intact cells of the same strain.