Continuous production ofL-malic acid by immobilizedBrevibacterium ammoniagenes cells

Summary Continuous production ofL-malic acid from fumaric acid using immobilized microbial cells was investigated. Several microorganisms having fumarase activity were immobilized into a polyacrylamide gel lattice. Among the microorganisms tested, immobilizedBrevibacterium ammoniagenes IAM 1645 showed the highest enzyme activity, but produced an unwanted by-product, succinic acid. Conditions for suppression of this side reaction were investigated, and bile extract treatment of immobilized cells was found to be effective.The bile extract treatment of immobilized cells also resulted in a marked increase of reaction rate forL-malic acid formation.No difference was observed between the native enzyme and immobilized cells in optimal pH and temperature of the enzyme reaction.The effect of temperature on the reaction rate and the stability of fumarase activity of an immobilized cell column were investigated under conditions of continuous enzyme reaction. The decay of enzyme activity during continuous enzyme reaction was expressed by an exponential relationship. Half-life of the fumarase activity of the immobilized cell column at 37°C was calculated to be 52.5 days.Presented at the Annual Meeting of the Society of Fermentation Technology, Japan, Osaka, Japan, October 30, 1975.