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  • Authors: Duong Van Hop; Yayoi Sakiyama; Chu Thi Thanh Binh; Misa Otoguro; Dinh Thuy Hang; Shinji Miyadoh; Dao Thi Luong; Katsuhiko Ando (2011-04-07)

  • Actinomycetes were isolated from 109 soil and 93 leaf-litter samples collected at five sites in Vietnam between 2005 and 2008 using the rehydration-centrifugation (RC) method, sodium dodecyl sulfate-yeast extract dilution method, dry-heating method and oil-separation method in conjunction with humic acid-vitamin agar as an isolation medium. A total of 1882 strains were identified as Vietnamese (VN)-actinomycetes including 1080 (57%) streptomycetes (the genus Streptomyces isolates) and 802 (43%) non-streptomycetes. The 16S ribosomal RNA gene sequences of the VN-actinomycetes were analyzed using BLAST searches. The results showed that these isolates belonged to 53 genera distributed among 21 families. Approximately 90% of these strains were members of three families: Streptomycetaceae...

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  • Authors: Dao Thi Luong; Vi Dai Lam; Tran Thi Le Quyen; Ha Thi Hang; Pham Duc Ngoc; Duong Van Hop (2011-09-09)

  • A bacterial strain YS24 produced high level of extracellular protease was isolated from soil sample collected at Yen Son - Tuyen Quang. Based on the colony observation, cell morphology and the analysis of 16S rDNA nucleotide sequence, the strain YS24 was identified as Bacillus subtilis. The highest levels of extracellular protease production and bacterial growth were obtained by using medium V9 (g/l): Glucose-5; peptone-7.5; MgSO4.7H20-5; K2HPO4-5; FeSO4.7H20-0.1. Enzyme production corresponded with bacterial growth and reached a maximal level of 1,390 U/ml when the bacterium was cultured on the orbital shaker under following condition: at speed of 200 rpm, inoculum size of 7% , temperature of 40-45°C, medium pH of 7.0 -8.0 and incubation time in 48 hours. The best carbon source was...

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  • Authors: Phan Thi Phuong Hoa; Nguyen Duc Quang; Yayoi Sakiyama; Duong Van Hop; Dinh Thuy Hang; Trinh Hoang Ha; Nguyen Thi Van; Nguyen Thi Kim Quy; Nguyen Thi Anh Dao (2012-08-03)

  • Bacterial blight disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the major diseases in rice culture of Northen Vietnam, as well as other rice-growing regions of the world. In this study, we isolated and screened for actinomycete strains from Vietnam with the ability to inhibit Xoo isolates from northern Vietnam. From 90 actinomycete strains taken from soil in northern Vietnam in 2010, we screened for their antagonistic activity against 10 races of Xoo causing rice bacterial blight disease. Three actinomycete strains were found to inhibit all 10 Xoo races. Among the three strains, a strain namely VN10-A-44 was shown not to have the ability to produce toxic compounds and was selected for further study. The strain was identified as Streptomyces virginiae by 16S ribosoma...