Abstract
An enzymatic process has been proposed for producing L-lysine from DL-aminolactam by the author. Several yeasts, including Cryptococcus laurentii, have been isolated from soil and found to catalyze the selective hydrolysis of aminolactam. As well, several bacteria, including Achrornobacter obae nov. sp., have been isolated which catalyze the racemization of aminolactam. This paper reports an investigation of the conversion reaction of D- and DL-aminolactam into L-lysine using both cells of Crypt. laurentii and Achr. obae nov. sp. The optimum pH of the reaction was between 8.0 and 9.0, but most often near 8.0. An inhibitory effect of the substrates on the reaction was observed when the substrate concentration was higher than 10%, but the inhibition was slight at 5% substrate. The optimum temperature of the reaction for 3_??_6hr was around 39°C. A complete conversion reaction of 10% DL-aminolactam was carried out at 40°C for 24 hr, producing L-lysine in a conversion rate of 99.8 %. L-Lysine•HCl isolated from the reaction mixture was 99.5% optically pure.
