Investigation of the prebiotic properties of the yam bean (Pachyrhizus erosus (l.) urban) tuber extract

Abstract

Yam bean tubers have been found to possess various kinds of fructans including inulin and fructooligosaccharide, which are well-known prebiotics. However, the prebiotic effects of yam bean tuber have not been established. This study was aimed to investigate the prebiotic properties of the yam bean tuber extract. The sample was prepared by extracting the edible tubers of yam bean with 85% ethanol. The prebiotic effects of the yam bean tuber extract (1, 2, 3%) were evaluated by monitoring bacterial growth and acid production of the probiotics, Lactobacillus plantarum and Lactobacillus acidophilus. The results showed that yam bean tuber extract produced significant concentration-dependent increases in the growth and acid-producing activity of L. plantarum (p<0.05). The specific growth rate and generation time of L. plantarum was significantly modified by the yam bean tuber extract at the highest concentration tested (3%) (p<0.05). The extract also caused a significant pH decrease in the L. acidophilus incubation media (p<0.05). However, the growth kinetics, specific growth rate and generation time of L. acidophilus did not change significantly. The extract did not substantially influence the growth kinetics, specific growth rate, and generation time of Escherichia coli, the pathogenic bacteria. The effects of the yam bean tuber extract on the growth and acid production of bacteria were similar to those of the commercial inulin at the same concentrations tested. These results indicate the prebiotic properties of the yam bean tuber extract in certain probiotics, specifically L. plantarum.