• Microbiology and Biotechnology Letters
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• v.34 no.2
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• pp.109-114
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• 2006

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.

• Journal of Microbiology and Biotechnology
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• v.14 no.5
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• pp.952-958
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• 2004

Of 23 psychrotrophic bacteria isolated from the west Pacific deep-sea sediments, 19 were assigned to the $\gamma$-Proteobacteria, 3 to the <$\beta$-Proteobacteria, and 1 to the Gram-positive bacteria, as determined by their 16S rDNA sequences. Ten psychrotrophs, affiliated to the Psychrobacter, Pseudoalteromonas, and Pseudomonas genera in the $\gamma$-Proteobacteria group, were screened for lipolytic bacteria. The majority of the lipolytic isolates had growth temperatures between 4-$30^\circ{C}$, and all of them were neutrophilic, aerobic, or facultatively anaerobic, and some were able to produce multiple kinds of ectohydrolytic enzymes. The deep-sea strains Psychrobacter sp. wp37 and Pseudoalteromonas sp. wp27 were chosen for further lipase production analysis. Both strains had the highest lipase production when grown at 10 to $20^\circ{C}$; their highest lipase production occurred at the late-exponential growth stage; and the majority of the enzymes were excreted to the outside of the cells. Lipases from both strains had the same optimal reaction temperature and pH (20-$30^\circ{C}$, pH 7-8) and could retain about 60% of their highest activity at $4^\circ{C}$. Furthermore, SDS-PAGE and an in-gel activity test showed that they had the same high molecular mass of about 85 kDa.