INCREASING PRODUCTIVITY BY REMOVING CHOLINE IN CONVERSION OF PHOSPHATIDYLCHOLINE TO PHOSPHATIDYLSERINE BY PHOSPHOLIPASE-D

The conversion of phosphatidylcholine (PC) to phosphatidylserine (PS) was examined in the presence of L-serine (3.4 M, solubility of serine) using two phospholipase D (PLD) preparations of Streptomyces origin. A biphasic reaction was carried out at 30-degrees-C using an aqueous phase containing both PLD and serine and a solvent (ethyl acetate or diethyl ether) phase containing PC. With an increase in the PC concentration from 17.8 mM to 106.8 mM, the conversion decreased from 85% to 36% in 30 min. The effect of choline inhibition was investigated in two ways-by the addition of choline chloride at low PC concentrations and by removing choline enzymatically or physically during the progress of the reaction at high PC concentrations. The addition of various concentrations of choline chloride decreased the reaction rate, conversion and selectivity. The unreacted PC decreased from 36% to 17.6% and further to 1.6% by the addition of choline oxidase and a mixture of choline oxidase and catalase, respectively. There were no decreases in either the selectivity or the final PS content for the ten repeated batches examined when choline released was washed out from the PLD gels immobilized in Octyl-Sepharose CL-4B after each run.