SYNTHESIS OF L-TRYPTOPHAN BY IMMOBILIZED ESCHERICHIA-COLI-CELLS

Enzymatic production of L-tryptophan has been studied in a system containing Escherichia coli cells (induced for tryptophanase) entrapped in a polyacrylamide gel, indole and excess pyruvate and ammonia. The influence of pH, substrate concentration and temperature on L-tryptophan production, in batch and flow reactor conditions, was investigated. In flow reactor conditions, inhibition of the reaction by indole resulted in a multi steady-state pattern characteristic of substrate inhibited reactions. Any increase in flow rate at indole concentrations higher than 17 mM resulted in a dramatic decrease in the conversion rate of indole to tryptophan. A device for the practical production of L-tryptophan, which involves feeding a limiting concentration of indole to a reactor, adsorption of the synthetized tryptophan and recycling of excess pyruvate and ammonium ions was tested. © 1979 Springer-Verlag.