The use of l-lysine decarboxylase as a means to separate amino acids by electrodialysis

Abstract

Amino acids (AA's) are interesting materials as feedstocks for the chemical industry as they contain chemical functionalities similar to conventional petrochemicals. This offers the possibility to circumvent process steps, energy and reagents. AA's can be obtained by the hydrolysis of potentially inexpensive voluminous protein streams derived from biofuel production. However, isolation of the preferred AA is required in order to carry out further transformation into the desired product. Theoretically separation may be achieved using electrodialysis. To increase efficiency, specific modification to a product of industrial interest and removes charged groups of AA's with similar isoelectric points is required. Here, the reaction of L-lysine decarboxylase (LDC) was studied as a means to specifically convert L-lysine (Lys) to 1,5-pentanediamine (PDA) in the presence of L-arginine (Arg) to produce products with different charge thus allowing isolation of products by electrodialysis. Immobilization of LDC in calcium alginate enhanced the operational stability and conversion in mixtures of amino acids was highly specific. At 30 °C the presence of Arg had little effect on the activity of the enzyme although inhibition by the product PDA could be observed. Volumetric productivity was calculated and raw material and transformation costs were estimated for a potential process using a mixture of Arg and Lys.