Digestion and fermentation of pullulan.

Abstract

The hydrolysis in the digestive tract of pullulan, a microbial polysaccharide, was examined by an in vitro digestion method. Pullulan was partially hydrolyzed by salivary and pancreatic amylases without glucose formation. No hydrolysis was observed using artificial gastric juice. Small-intestinal enzymes hydrolyzed pullulan to lower molecules, producing a small amount of glucose (2.7%). Micro-bial fermentation of pullulan in the large intestine was examined using an in vitro fecal culture system. Pullulan was fermented to short-chain fatty acids (mainly acetic, propionic and n-butyric acids) as the hindgut fermentation products. Under anaerobic incubation, the carbon recovery of short-chain fatty acids was 47.8%. The behavior of pullulan in the digestive tract was thus clarified using this diges-tion method and fecal culture system.