GROWTH AND KAPPA-CARRAGEENAN IMMOBILIZATION OF PSEUDOMONAS-DACUNHAE CELLS FOR L-ALANINE PRODUCTION

Industrial production of L-alanine is accomplished from L-aspartic aci d using L-aspartate beta-decarboxylase (ADL) enzyme of resting Pseudom onas dacunhae cells as the biocatalyst. This work reports on the effec t of inoculation ratio, agitation rate, and pH control on the cell con centration and enzyme activity during the growth as well as the effect s 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 incr eased 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 t he immobilized cells were treated with the cross-linking agents hexame thylenediamine (HMDA) and glutaraldehyde (GA). Pellet size and agitati on rate investigations showed that intraphase mass transfer limitation s are present. An increase in the pellet concentration increased the i nitial reaction rate but its effect was not very significant after 100 kg m(-3) Optimum initial pH range far the L-alanine production reacti on 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 cel ls and the P-8 pellets, respectively. Substrate activation mechanism w as valid for the L-alanine production with the free cells while for th e P-8 pellets Michealis-Menten mechanism was satisfactory. (C) 1998 El sevier Science Inc.