Bioconversion of trans-cinnamic acid to l-phenylalanine by l-phenylalanine ammonia-lyase of Rhodotorula glutinis: Parameters and kinetics

The kinetics of the bioconversion of trans-cinnamic acid to l-phenylalanine by the l-phenylalanine ammonialyase (PAL) enzyme of resting cells of Rhodotorula glutinis have been studied under the optimum bioreaction conditions determined. The optimum pH, temperature, ammonia concentration, and biocatalyst loading were 10.5, 30°C, 8 m, and ca. 2 (w/w), respectively. Among various chemicals, sodium glutamate and penicillin were found to increase the PAL activity of the cells. A maximum concentration of 76.18 m m (12.57 g dm −3) l-phenylalanine was maintained from 100 m m (14.8 g dm −3) trans-cinnamic acid after 104 h of residence time in the fed-batch operation of the bioreactor. trans-Cinnamic acid concentrations higher than 30–50 m m were shown to cause the substrate inhibition, besides the mixed-type inhibition effect of the chloride ions. Mechanistic bioreaction rate equations that incorporate separately the inhibition effects of the trans-cinnamic acid and chloride ions, and the activation effect of sodium glutamate, were proposed and the kinetic parameters of the models were calculated.