Release of Methanol and Depolymerization of Highly Methyl Esterified Apple Pectin with an Endopolygalacturonase from Aspergillus nigerand Pectin Methylesterases from A. nigeror from Orange

Abstract

In order to obtain a better understanding of pectin hydrolysis during enzymatic clarification of apple juice, de-esterification of highly methyl esterified pectins (degree of methoxylation 100 or 95) was studied using two pectin methylesterases (PME) from fungus or plant, and the depolymerization of these pectins with an endopolygalacturonase (PG) from Aspergillus niger. The behaviour of three markers was studied: (a) released methanol, (b) hydrodynamic volume of the polysaccharide, and (c) tri-, di- and monogalacturonic acids, which are final products of hydrolysis. The combination of PME from A. nigerand PG led to a progressive degradation of the pectin chains. In contrast, the combination of PME from orange and PG first increased methanol release but later the esterase activity seemed to be rapidly inhibited by polymeric and oligomeric chains. Depolymerization of the pectin chain was correlated with the content of released methanol whatever the origin of the PME but, for the same amount of released methanol, the PG action was more effective on pectin de-esterified with fungal PME.