Scale-up of D-lysine production from L-lysine by successive chemical racemization and microbial asymmetric degradation

In order to develop an industrial production process of D-lysine from L-lysine, successive chemical racemization and a microbial asymmetric degradation were investigated in a pilot scale. The racemization of L-lysine proceeded quantitatively. The cultivation conditions of Comamonas testosteroni for L-lysine degradation were optimized in a 30L jar fermenter and scaled-up to 5m tank. The L-lysine-degrading reaction was performed by using racemized lysine crystals as substrate and C. testosteroni IAM 1048 intact cells as biocatalysts. Crystalline D-lysine, with a chemical purity greater than 99% and optical purity of 99.9% enantiomeric excess, was obtained at a yield of 36% from the reaction mixture by simple purification. On the basis of these results, we have designed a process for a large scale production of D-lysine.