Volume 19 Part 1 Article 59
Title: Water-Soluble Polysaccharides from Pleurotus pulmonarius are resistant to human digestion system
Author: Kimteck Leow and Ahmad Rosma
Water-soluble polysaccharides were extracted from Pleurotus pulmonarius which will be formulated for food ingredient with prebiotic functionality. To enable food or food component to act as prebiotic, it must first be resistant to acid hydrolysis in the stomach and remain non-digestible by human digestive enzymes. In this study, the in vitro digestibility of the water-soluble polysaccharides (WSP) from Pleurotus pulmonarius was investigated against mammalian gastric and pancreatic juices. The WSP was prepared by hot water extraction method and was partially purified via protein removal process. The digestibility of the WSP was determined by calculating the degree of its hydrolysis (based on amount of released reducing sugars) when subjected to artificial human gastric and porcine pancreatic juices. The WSP contained 54.0 % of polysaccharides in which total glucan constituted 31.3 % and non-glucan polysaccharides constituted the remaining 22.7 %. The total glucan was found consisted of 23.5 % of β-glucan and 7.8 % of α-glucan. The WSP was found contaminated with minimal amount of protein (1.94%) and the moisture content of WSP was relatively low (8.70 %). The FT-IR spectra of the WSP was also identical to the FT-IR spectra of the purified β-glucan. Compared to the commercial reference prebiotics [Fructo-oligosaccharide (FOS) and Inulin], which were less stable in the strong acidic environment; the mushroom water-soluble polysaccharides showed much higher degree of resistance to artificial human gastric juice. WSP was highly resistant to both weak (pH 3-5) and strong acidic environment (pH 1-2) and its resistance was not affected by pH of the artificial human gastric juice. In contrast, the resistance of both FOS and Inulin substrates were significantly lower in strong acidic environment (pH 1 and pH 2) than in weak acidic environment (pH 3, pH 4 and pH 5). Under small intestine environment, the corresponding order for hydrolysis by porcine pancreatic juice was WSP > FOS > Inulin. In conclusion, the mushroom WSP is resistant to acid hydrolysis in the stomach and almost non-digestible by human digestive enzymes. The resistance of the tested substrates towards artificial human digestion system followed the order: WSP > Inulin > FOS. The finding also suggests that the WSP from Pleurotus pulmonarius fulfil the first prebiotic criteria.