REDUCTIONS OF 3-OXO ESTERS BY BAKERS-YEAST - CURRENT STATUS

The objective of the current review is lo present a mechanism and proc ess engineering approach of stereospecific reductions of 3-oxo esters by baker's yeast. The stereospecific outcome of a reduction by baker's yeast depends on the kind of 3-oxo ester reductases involved and thei r specific activity. Various competing 3-oxo ester reductases are pres ent in a yeast cell. An important aspect for efficient biotransformati ons with whole cells is the regeneration of NADH and NADPH cofactors. Use of different electron donors leads to the involvement of different metabolic routes influencing the reduction process. Optimization of t he process conditions such as aeration, immobilization of cells, use o f additives, or use of two phases, will enhance re-use of baker's yeas t yield, stereospecific outcome and scale up. Since the genome of bake r's yeast is known: genetic engineering will soon increase the possibi lities of stereoselective reductions.