Effects of chemical modification on the stability of invertase before and after immobilization

Invertase from baker's yeast immobilized by coupling the amino acid side-chain amino groups or glycosyl residues to the matrix has been studied for its resistance to heat and urea-induced denaturation, to understand the influence of the nature of immobilization procedure on these processes. The possible role of chemical modifications and/or carbohydrate depletion to which the enzyme was subjected was also examined by investigating the properties of soluble modified enzyme. The immobilized preparations obtained were Sp-INV by direct coupling of invertase to Sepharose, Sp-PEA-INV by coupling of periodate and ethanolamine-treated invertase to Sepharose, Sp-PEDA-INV by coupling of periodate and ethylenediamine-treated invertase to Sepharose, and Sp-PEDA-2-4-6-trinitrobenzene sulfonic acid (TNBS)-INV by coupling of TNBS followed by periodate and ethylenediamine-treated invertase to Sepharose. All of the immobilized preparations exhibited higher stability against heat and urea-induced inactivation as compared to native invertase, Among the procedures employed for immobilization of invertase, the Sp-PEDA-INV preparation exhibited highest yield of immobilization, eta value, and thermal and storage stability. The yield of immobilization and stabilization was followed by Sp-PEA-INV, Sp-INV, and Sp-PEDA-TNBS-INV preparations.