Kontinuierliche Reaktionsführung mit löslichen Enzymen

Continuous processes with soluble enzymes. This paper surveys the use of continuously operating enzyme-membrane reactors with enforced flow where the retention of soluble enzymes in the reaction vessel is achieved by means of an ultrafiltration membrane. This technique has been commercialized in the acylase process for the synthesis of L -amino acids on a 200 ton/year level. It is especially useful for the application of multi-enzyme systems with cofactor regeneration. The synthesis of L -tert-leucine from the corresponding α-keto acid has been achieved on a kilogram scale. Coenzymes coupled to water soluble polymers are retained in the membrane-reactor together with the enzymes. Use of suitable conditions prevents loss of enzyme and coenzyme by passage through the membrane or by deactivation. Therefore the costs of enzymes and coenzymes are no longer limitations for economic processes. In the continuously operating enzyme-membrane reactor regeneration of the coenzyme up to 600 000 times was achieved. In continuous peptide synthesis space-time yields of 25 kg/(l d) were obtained. To suppress side reactions very high catalyst concentrations are possible, yielding residence times below 4 min.     

Mathematical modelling of NADH oxidation catalyzed by new NADH oxidase from Lactobacillus brevis in continuously operated enzyme membrane reactor

NADH oxidase from Lactobacillus brevis was kinetically characterized in two different buffers: Tris-HCl and glycine-sodium pyrophosphate (pH 9.0). Reaction kinetics was described using the Michaelis-Menten model with product (NAD(+)) inhibition. It was found that this type of inhibition is uncompetitive. Experiments in the continuously operated enzyme membrane reactor revealed a strong enzyme deactivation at two different residence times: 12 and 60 min. A stronger deactivation was observed at the lower residence time in the glycine-sodium pyrophosphate buffer. Enzyme deactivation was assumed to be of the first order. The developed mathematical model for the continuously operated enzyme membrane reactor described these experiments very well. The mathematical model simulations revealed that a high enzyme concentration (up to 30 g cm(-3)) is necessary to obtain and maintain the stationary NADH conversion near 100% for a longer period of time.