Enzymatic Degradation of Starch—Usage of β‐Cyclodextrin for Inactivation of Pullulanase

Abstract

AbstractThe cyclic oligosaccharide β‐cyclodextrin (β‐CDx) is investigated regarding its ability on principle to reduce the debranching activity of pullulanase (PUL) or even terminate the enzymatic hydrolysis process of starch polymers completely. For this purpose, dissolved β‐CDx (aqueous solution) is mixed with the diluted PUL compound (solution) and conditioned (stirred at 40 °C for various durations [0, 20, 40, and 60 min; at 26.75 nmol β‐CDx U−1] and at various β‐CDx dosages [5.35, 13.375, 26.75, and 53.5 nmol β‐CDx U−1; reaction time 60 min]). The PUL‐CDx‐mixtures are subsequently added to a 2.5% w/w starch solution (related to the initial specific debranching activity; 1593.6 NPUN g−1/557.8 U g−1) and gently stirred for 20 min at 40 °C before final thermal inactivation. The obtained samples are diluted and characterized molecularly, i.e., by means of size exclusion chromatography (SEC). An increasing β‐CDx dosage reduces the degree of molecular degradation systematically reflecting a successively reduced enzyme activity. However, the reaction time (PUL‐CDx‐mixture) has no impact on the enzyme's activity since the starch degradation is marginally and the SEC‐chromatograms similar to the one of the initial starch. Restrictions of the enzyme inhibiting effect of β‐CDx are found terminating the hydrolysis process in a starch suspension.