Enzymatic degradation of epichlorohydrin crosslinked starch microspheres by α-amylase

Purpose. The influence of chemical parameters on the sensitivity to enzymatic degradation by alpha-amylase of starch microspheres crosslinked by epichlorohydrin was studied. Methods. Starch microspheres were prepared using epichlorohydrin as a crosslinking agent. Their swelling degree, reflecting the number of glycerol diether bridges in the polymeric network, and the number of non-crosslinking monoglycerol ether groups corresponding to a side-reaction of epichlorohydrin with starch were determined. Degradation rates of the microspheres in presence of porcine alpha-amylase were deter mined by a microvolumetric method. Results. Degradation by alpha-amylase was surface-controlled and could be modulated by the introduction in the polymeric network of: (i) nonhydrolysable 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 likely to block, the activity of alpha-amylase. In the case of highly cross-linked microspheres, the number of glycerol monoether pendent chains had a predominant effect on the degradation rate which ranged between 10(-2) and 10(-5) min(-1). Conclusions. It was possible to modulate simultaneously the swelling. degree and the enzymatic degradability of starch microspheres by adjusting the chemical parameters during the crosslinking reaction.