APTES modified SBA15 and meso-macro silica materials for the immobilization of aminoacylases from Streptomyces ambofaciens

Abstract

Aminoacylases from a crude extract from Streptomyces ambofaciens were described as attractive way for the synthesis of amino acids biobased surfactants. The aim of this study is to investigate the influence of the porosity and the APTES functionalization of the silica support on the immobilization and the activities of these aminoacylases. To reach this goal, a mesoporous (SBA-15) and of meso -macroporous (MMS) silica material without and with functionalization with APTES were used. The results show that the use of non-functionalized supports led to a poor enzyme loading due to electrostatic repulsion between the enzyme and the silica support. The APTES functionalization of the silica materials allow a better enzyme loading by favouring enzyme-support interactions with an increase of the immobilization rate by increasing the APTES functionalization rate from 0 to 10% especially when using MMS. However, the measurement of the catalytic performances of the enzymes immobilized on the materials shows a significant improvement of the conversion rate by increasing the APTES percentage in the case of SBA-15 unlike the enzymes immobilized on the functionalized MMS. This behaviour can be explained by the better substrate accessibility to the enzyme immobilized on the SBA-15-based materials which is mainly located on the external surface area of the functionalized materials. The cross linking of the aminoacylases by using glutaraldehyde led to a loss of the activity due to enzyme inactivation. The LC-MS-MS analysis of the product of lysine acylation reaction shows that the regioselectivity of the enzymes after immobilization is not modified. • Improvement of the immobilization rate and the activity of the immobilized enzymes by increasing the APTES concentration. • No effect of the porosity on the immobilization performance. • Collapse of the structure of the mesomacroporous material after immobilization led to a diffusional limitation. • Structural stability of the SBA-15 material after immobilization. • Decrease of the activity after the addition of glutaraldehyde.