Enhanced activity of yqhD oxidoreductase in synthesis of 1,3-propanediol by error-prone PCR

yqhD oxidoreductase was determined to be an NADP-dependent dehydrogenase, and was more active toward 3-HPA when compared to 1,3-propanediol oxidoreductase. To further improve enzyme activity towards 3-hydroxypropionaldehyde (3-HPA), error-prone PCR was implemented to mutant yqhD gene. Two mutants, D99QN147H and Q202A with increased catalytic and affinity efficiency, were obtained after one round of error-prone polymerase chain reaction. And the catalytic efficiency of the mutant D99QN147H was up to 4-fold greater than the wild enzyme (0.0375 min−1 mM−1 vs. 0.0078 min−1 mM−1). The recombined strain containing pET28yqhD D99QN147H yielded 28 g L−1 of 1,3-propanediol in the fed-batch LB cultures (1 L volume) with an initial 3-HPA concentration of 40 g L−1, which was higher than the 21 and 17 g L−1 of 1,3-propanediol from the mutant Q202A and the wild-type, respectively. Except for propionaldehyde, the optimal mutant D99QN147H also exhibited higher activity on a range of substituted aldehydes than the wild-type.