Enzymatic catalysis dynamics of preparation of D-phenylalanine

The Burkholderia cepecia 1003 screened by the authors' laboratory, which contained hydantoinase and N-carbamoylase activities, was used to prepare D-phenylalanine on a large scale. The dynamic parameters of the whole bioconversion process were measured, and the results showed that k_r was 3.975×10^-3 min^-1, K_m and r_m of hydantoinase and N-carbamoylase were 16.7894 mmol ·L^-1, 0.82688 mmol·L^-1, 0.6127 mmol·L^-1·min^-1 and 4.828×10^-4 mmol·L^-1·min^-1, respectively. Simulation was made including processes of dissolution of DL-BH, racemization of L-BH, hydrolysis of D-BH and hydrolysis of N-carbamyl phenylalanine. The significance of parameters in this model was investigated and these parameters were optimized. The results showed that the reaction rate of D-BH hydrolysis was higher than that of N-carbamyl phenylalanine hydrolysis, and the latter was the limiting step of the whole process. Promotion of N-carbamoylase activity was helpful to D-phenylalanine production. The rate of L-BH racemization was the main factor, which influenced the conversion of racemic BH.