Growth and κ-carrageenan immobilization of Pseudomonas dacunhae cells for L-alanine production

Industrial production of L-alanine is accomplished from L-aspartic acid using L-aspartate beta-decarboxylase (ADL) enzyme of resting Pseudomonas dacunhae cells as the biocatalyst. This work reports on the effect of inoculation ratio, agitation rate, and pH control on the cell concentration and enzyme activity during the growth as well as the effects of different kappa-carrageenan-immobilization procedures applied to the active cells and the kinetics of the biocatalyst pellets. Although the cell concentration was not affected lower inoculation ratios increased the activity of the produced enzyme. Both the cell concentration and the ADL activity increased with the agitation rate. The activity and the stability of the biocatalyst pellets were retained more when the immobilized cells were treated with the cross-linking agents hexamethylenediamine (HMDA) and glutaraldehyde (GA). Pellet size and agitation rate investigations showed that intraphase mass transfer limitations are present. An increase in the pellet concentration increased the initial reaction rate but its effect was not very significant after 100 kg m(-3) Optimum initial pH range far the L-alanine production reaction for the free and HMDA + GA-treated immobilized cells (P-8 pellets) were 6.0-6.2. Optimum temperature was 323 K and 333 K for the free cells and the P-8 pellets, respectively. Substrate activation mechanism was valid for the L-alanine production with the free cells while for the P-8 pellets Michealis-Menten mechanism was satisfactory. (C) 1998 Elsevier Science Inc.