Yam has been recognized as healthy food due to its various biological activities, such as anti-obesity, antimicrobial, anticancer and immuno-stimulation activities, and its consumption has been increased during last decades. In this study, to investigate low-temperature, long-term storage of yam and to develop processed yam products, yam-putrefactive psychrotrophic bacteria were isolated from rotted yam and identified based on BBL identification system, fatty acid analysis in cell membrane and 16S rDNA sequence analysis. The putrefaction activity of isolated thirteen bacteria was evaluated using yam-slices (NaOCl-treated, autoclaved yam and without treatment), and YAM-10 and YAM-12 were identified as major psychrotrophic putrefactive bacteria. Both YAM-10 (Pseudomonas cepacia) and YAM-12 (Pseudomonas rhodesiae) bacteria grew well at 4$sim$12$^{circ}C$ and showed strong activity of polymer degrading enzymes, especially amylase, carboxy methyl cellulase and xylanase, at 20$^{circ}C$. But they failed to grow at acidic pH (<5) or alkaline pH (>10). Our results suggested that the control of psychrotrophic Pseudomonas sp. by pH change and inhibition of polymer degrading enzymes, such as amy-lase, are necessary to long-term storage of yam.