the present invention provides recombinant plasmids containing a gene coding for polyhydroxyalkanoate biosynthesis enzyme and a gene coding for intracellular pha depolymerase , and a process for preparing - hydroxycarboxylic acid employing the same . in accordance with the present invention , optically pure - hydroxycarboxylic acid can be prepared by culturing e . coli transformed with a recombinant plasmid which expresses intracellular pha depolymerase of ralstonia eutropha and pha biosynthesis enzyme of alcaligenes latus to give - hydroxycarboxylic acid . the process for preparing - hydroxycarboxylic acid of the invention can be successfully employed in large - scale continuous process with a high productivity by carrying out pha synthesis and degradation in a simultaneous manner , while enjoying the benefits of simple procedures for harvesting cells and disposing the cell wastes .