Immobilization of Pseudomonas sp. BA2 by entrapment in calcium alginate and its application for the production of l-alanine

Abstract

The conditions for immobilizing the new l-aminoacylase-producing bacterial strain Pseudomonas sp. BA2 by entrapment in calcium alginate gel were investigated. The optimal gel concentration and cell loading were determined. It was demonstrated that the addition of the substrate n-acetyl- l-alanine to the immobilizing matrix enhanced l-aminoacylase activity. The enzymatic properties of immobilized Pseudomonas sp. BA2 were investigated to ascertain which conditions were suitable for the enzymatic reaction. Optimal pH, temperature, and concentration of Tris-maleate buffer were determined. The influence of adding CoCl 2 on the enzymatic reaction rate was studied and the optimal concentration of the activator was determined. Stability studies showed that the immobilized cell preparation is not adequate for use in repeated batch processes. Continuous operation in a stirred tank reactor allowed us to determine the biocatalyst half-life (7 h approximately) but, due to the high l-aminoacylase activity, the reactor productivity (24.5 mmol of l-alanine in 8 h) was noticeably higher than that previously obtained in a packed bed reactor with Aspergillus ochraceus pellets. The results reported in this paper show the potential for using the immobilized Pseudomonas sp. BA2 in calcium alginate to produce l-alanine; however, before large scale production can be undertaken, further biocatalyst stabilization studies have to be made.