X. Li

AIMS: Production of isomaltulose by newly isolated Klebsiella sp. LX3. METHODS AND RESULTS: The bacterial isolate LX3, which transforms sucrose to isomaltulose and trehalulose, has been isolated from a soil sample in Singapore. Morphological and biochemical analysis, as well as 16s rRNA sequence demonstrated that the isolate could represent a new member of genus Klebsiella. The strain has several interesting features. The immobilized cells of Klebsiella sp. LX3 convert more than 99% of sucrose to products that consist of more than 87% of isomaltulose, 11.6% of trehalulose, and <1% of glucose. CONCLUSIONS: The production of isomaltulose synthase in isolate LX3 is inducible by its substrate sucrose and the sugars containing a fructofuranosyl group. SIGNIFICANCE AND IMPACT OF STUDY: It would be useful for future biotechnological applications to understand the structural features or motifs of the isomaltulose synthases that determine the sucrose conversion efficiency and the ratio of the conversion products.

AIMS: Isolation and characterization of the xanthan-degrading Microbacterium sp. XT11. METHODS AND RESULTS: The bacterial isolate XT11, capable of fragmenting xanthan, has been isolated from soil sample. Morphological and biochemical analyses, as well as 16S rRNA gene sequence comparisons, demonstrated that strain XT11 should be grouped in the genus Microbacterium, and represented a new member in this family. Xanthan could be degraded by the xanthan-degrading enzyme released from strain XT11. It has been shown that xantho-oligosaccharides fragmented from xanthan had both elicitor activity and antibacterial effect against Xanthomonas campestris pv. campestris. CONCLUSIONS: The xanthan-degrading enzyme produced by the newly isolated XT11 could fragment xanthan to form oligosaccharides. SIGNIFICANCE AND IMPACT OF THE STUDY: Xanthan-degrading products would be useful for potential application in the control of black rot of cruciferous plants caused by X. campestris pv. campestris and, as an oligosaccharide elicitor, in making these plants resistant to disease.

Certain factors affecting the production of cell‐associated α‐galactosidase by Bacillus sp. JF2 were investigated. The intention was to maximize α‐galactosidase activity of potential commercial application, by consecutive optimization of growth media and conditions. The highest α‐galactosidase activity was obtained when grown on melibiose, whereas sucrose inhibited the production of α‐galactosidase. α‐Galactosidase production was optimally active at pH 7·5 and 55°C. It was identified that a soy effluent stream could be used as the best carbon source for α‐galactosidase by Bacillus sp. JF2.

AIMS: To isolate and characterize an oxalate-degrading Pandoraea sp. OXJ-11. METHODS AND RESULTS: A new bacterium Pandoraea sp. OXJ-11 was isolated from soil samples, which can grow in the medium with oxalate as the sole carbon and energy source. The isolate OXJ-11 is Gram-negative straight rod. It occurs singly and is motile by means of a double polar flagellum. Catalase is positive and nitrate is not reduced. It grows aerobically and the optimum growth temperature and the optimum pH are at 30 degrees C and pH 6.0, respectively. The polyphasic taxonomic data along with 16S rRNA sequence comparison demonstrate that the isolate OXJ-11 should belong to the genus Pandoraea and represent a new member in this family. CONCLUSIONS: Oxalate could be degraded and the oxalate-degrading enzyme activity was detected when the isolate OXJ-11 grew in the medium with oxalate as carbon source. SIGNIFICANCE AND IMPACT OF THE STUDY: Oxalate-degrading Pandoraea sp. OXJ-11 would be beneficial to the potential application in the control of sclerotinia stem rot in economically important plants caused by fungus Sclerotinia sclerotiorum, and in making plants resistant to the white mold disease by oxalate-degrading enzyme transgene.

&nbsp;Macrolide antibiotics are widely used for treatment of community-acquired infectious diseases, but its side effects have not been thoroughly investigated, especially on the intestinal tract. Erythromycin, roxithromycin and azithromycin are macrolide antibiotics sharing similar&nbsp;chemical&nbsp;structure&nbsp;and their side effects on intestinal microflora of BALB/c mice were tested in this study. The bacterial composition of microflora was determined by 16S rRNA gene analysis conducted by polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE). The dominant bands were selected and sequenced to determine each individual bacteria. The total amount of 16S rRNA gene was reduced after macrolide antibiotics were administrated, and the specific pattern of bacterial composition was identified from each drug treatment.&nbsp;Bacteroides&nbsp;sp.&nbsp;and&nbsp;Clostridium butyricum str.&nbsp;were dominant intestinal organisms in all three drug-treated mice. This study reveals a significant change of bacterial composition of microflora on the tested mice for macrolide antibiotics. &nbsp; Key words:&nbsp;Macrolide antibiotics, side effects, intestinal microflora, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE).&nbsp;