Evidence of structural changes of an enzymatic extract entrapped into alginate beads

In this work, we analyzed the structural changes of araujiain entrapped into alginate beads. Araujiain is an enzymatic preparation containing three known enzymatic fractions with each fraction individually presenting a similar catalytic performance. Fluorescence and infrared spectroscopy, thermal analysis and residual catalytic activity studies were carried out. A small red shift in the spectrum of araujiain was observed after the entrapment process. Changes in the polarity around the tryptophan (Trp) residues were associated with an enzyme conformational change. From the Fourier transform infrared spectroscopy (FTIR) analysis, it was demonstrated that interactions between the enzyme extract and Ca alginate caused different structural behavior in araujiain. According to the diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) study, it was possible to conclude that a secondary structure with a high a-helical character was responsible for the highest activity of entrapped araujiain. Finally, from thermal analysis measurements, it was proved that entrapment of araujiain augments the thermal stability of both the enzyme extract and Ca alginate, indicating a possible interaction between enzyme extract and its support. (C) 2012 Elsevier B.V. All rights reserved.