Environmentally benign subcritical 1,1,1,2-tetrafluoroethane(R134a)was successfully used as a medium for enzyme-catalyzed synthesis.Phospholipase D-mediated transphosphatidylation to phosphatidylserine (PS)from phosphatidylcholine(PC)was performed in subcritical R134a and the influence of several parameters (enzyme loading,pressure,temperature,water addition and substrates)on the conversion was investigated.The results indicated that Phospholipase D was active in subcritical R134a at 303-323K and 2-8 MPa.Subcritical R134a reaction mixture resulted in enhancing the reaction kinetics with respect to conventional organic solvent system,requiring lower enzyme concentrations desired at commercial industrial scales.Higher velocity and conversion were observed with respect to those attained in conventional organic solvents.A maximum PS content of 84.88% was attained at 6 MPa,313K,after 240 minutes with 9.6 units phospholipase D.