Efficient biocatalytic production of D-4-hydroxyphenylglycine by whole cells of recombinant Ralstonia pickettii

The first establishment of a homologous expression system in the host Ralstonia pickettii CGMCC1596 using the compatible broad-host-range plasmid pWB5 is described. When whole cells of the recombinant strain R. pickettii MMYY01 (CGMCC1596/pYY05) were used as the biocatalyst to transform DL-4-hydroxyphenylhydantoin (DL-HPH) to D-4-hydroxyphenylglycine (D-HPG), the conversion rate reached 94 % in first 9 h, at a production rate of 2.8 g L(-1) h(-1), with the rapid reduction of the intermediate [N-carbamoyl-2-(4-hydroxyphenyl)glycine], compared with 80 % in >50 h at a rate of 0.5 g L(-1) h(-1) for the CGMCC1596. The stability of the recombinant plasmid pYY05 is sufficient for its application in industrial batch fermentation. An alternative strategy for the conversion of DL-HPH to D-HPG by resting CGMCC1596 cells and heterologous DCase expressed by E. coli is discussed.