• Journal of Microbiology and Biotechnology
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• v.16 no.1
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• pp.102-108
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• 2006

The IscA gene, encoding a levansucrase of 424 amino acids (aa) residues, was cloned from the genomic DNA of Pseudomonas aurantiaca S-4380, and overexpressed in Escherichia coli. The recombinant levansucrase overexpressed in E. coli was then used to produce levan from sucrose. Levan crystals with 98% purity could be obtained from the reaction mixture with $62\%$ yield using an alcohol precipitation method. The molecular weight of the levan was $7\times10^5$ daltons. Methylation studies showed that the levan was branched: main linkage C-2,6; branched linkage C-2,1; and degree of branching $6\%$. Three bacterial levans from different strains were incubated with levan fructotransferase (LFTase) from Arthrobacter ureafaciens K2032, which produced $di-\beta-D-fructofuranose$ dianhydride IV (DFA IV); final conversion yields from the levans to DFA IV were $39\%$ in Zymomonas mobilis, $53\%$ in Serratia levanicum, and $59\%$ in P. aurantiaca S-4380 levansucrase. The levan from P. aurantiaca S-4380 levansucrase gave the highest conversion yield of levan to DFAIV so far reported.

• Preventive Nutrition and Food Science
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• v.13 no.1
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• pp.1-6
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• 2008

Di-D-fructose-2,6':6,2'-dianhydride (DFA-IV) is a disaccharide consisting of two fructose residues that are prepared from levan by levan fructotransferase. Levan is a homopolysaccharide composed of D-fructofuranosyl residues joined by $\beta$-(2,6) and $\beta$-(2,1) linkages. We compared the immunomodulatory effects of levan with DFA-IV. Tumoricidal activity, phagocytosis and nitric oxide (NO) production were examined in levan- and DFA-IV-treated RAW264.7 cells. The NO production, tumoricidal and phagocytic activities were significantly increased in both treated cells. The results indicate that levan has significantly greater effects on tumoricidal activity than DFA-IV at low concentrations (1 ${\mu}g/mL$) and its effect on NO production shows a similar pattern. These results suggest that tumoricidal activity induced by both samples is mediated by NO production.