Characterization of glucomannan from Amorphophallus oncophyllus and its prebiotic activity in vivo

Porang (Amorphophallus oncophyllus) is local perennial plant rich in glucomannan. The aim of this study was to extract and characterize glucomannan from porang tuber and to evaluate its potency as prebiotic in vivo. The research consisted of the following steps, i.e. extraction of glucomannan, evaluation of its physico-chemical properties, and in vivo study. Extraction was done by immersing porang fluor with water at 55 °C followed by coagulating glucomannan using ethanol. Solubility, water holding capacity, viscosity, degree of acetylation, degree of polymerization (DP), and purity of the glucomannan were evaluated. In vivo study was done using thirty-two Wistar rats which were divided into four groups. Each group was treated for 14 days with standard AIN 93 (standard), porang glucomannan, commercial konjac glucomannan, and inulin diet as source of fiber. Bacterial population and chemical properties of digesta were analyzed after intervention. The results of the study indicated that the yield of glucomannan from porang flour was 18.05% with 92.69% purity. Compared to commercial glucomannan, porang glucomannan showed higher solubility (86.4%) and degree of acetylation (13.7%), but lower viscosity (5400 cps), WHC (34.5 g/g), and DP (9.4). Diet supplemented with porang glucomannan inhibited the growth of Escherichia coli, enhanced the production of total SCFA, and reduced pH value of cecal content. The study indicated that glucomannan from porang may be used as functional food.