Enzymatic degradation of epichlorohydrin crosslinked starch microspheres by alpha-amylase

Purpose. The influence of chemical parameters on the sensitivity to enzymat ic degradation by alpha-amylase of starch microspheres crosslinked by epich lorohydrin was studied. Methods. Starch microspheres were prepared using epichlorohydrin as a cross linking agent. Their swelling degree, reflecting the number of glycerol die ther bridges in the polymeric network, and the number of non-crosslinking m onoglycerol ether groups corresponding to a side-reaction of epichlorohydri n with starch were determined. Degradation rates of the microspheres in pre sence of porcine alpha-amylase were deter mined by a microvolumetric method . Results. Degradation by alpha-amylase was surface-controlled and could be m odulated by the introduction in the polymeric network of: (i) nonhydrolysab le alpha-1,6 bonds related to the presence of amylopectin in the raw starch , (ii) glycerol diether and, (iii) monoether groups, all of these being lik ely to block, the activity of alpha-amylase. In the case of highly cross-li nked microspheres, the number of glycerol monoether pendent chains had a pr edominant effect on the degradation rate which ranged between 10(-2) and 10 (-5) min(-1). Conclusions. It was possible to modulate simultaneously the swelling. degre e and the enzymatic degradability of starch microspheres by adjusting the c hemical parameters during the crosslinking reaction.