• Journal of Nutrition and Health
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• v.35 no.9
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• pp.903-911
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• 2002

The effects of dietary levan, high-molecular-weight $\beta$-2,6-linked fructose polymer, on adiposity, serum leptin and UCP expression in rats fed high fat diet were studied. The adipose tissue hormone, leptin has been proposed to be involved in the regulation of food intake and energy expenditure. Uncoupling protein (UCP), a mitochondrial protein that uncouples the respiratory chain from oxidative phosphorylation, generates heat instead of ATP, thereby increase energy expenditure. To determine whether the dietary levan may have the anti-obesity effect, 4 wk old Sprague Dawley male rats fed high fat diet for 6 wks to induce obesity, and subsequently fed one of three diets for further 6 wks: 1) high fat (40% of calories) diet without levan 2) with 3% (w/w) levan 3) with 5% levan. For the comparison, control group fed AIN-76A diet. Visceral and peritoneal fat masses were lower in high fat diet with levan groups compared to high fat diet group. The effect of levan was dose-dependent. Adipocyte size was significantly reduced in the levan diet groups compared to the no levan diet group. Serum cholesterol level was not affected by levan containing diet, while the serum HDL cholesterol level was higher in leven diet groups. In addition, serum triglyceride level was markedly reduced by levan containing diet, thus lower than that of control group. Serum leptin was reduced by levan containing diet and lower in 5% levan group compared to 3% levan group (p < 0.001), as a result, serum leptin and insulin levels of 5% levan group were reduced to level of control group. Futhermore, the serum leptin level reflected the adiposity. The expression of UCP 1, and UCP 2 in brown adipose tissue was up-regulated by levan containing diet. In conclusions, levan containing diet reduced adiposity and serum triglyceride but increased UCP expression in the obese rats fed high fat diet. (Korean J Nutrition 35(9) : 903~911, 2002)

• Journal of Microbiology and Biotechnology
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• v.31 no.5
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• pp.696-704
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• 2021

Levan is an industrially important, functional biopolymer with considerable applications in the food and pharmaceutical fields owing to its safety and biocompatibility. Here, levan-type exopolysaccharide produced by Pantoea agglomerans ZMR7 was purified by cold ethanol precipitation and characterized using TLC, FTIR, ¹H, and ¹³C NMR spectroscopy. The maximum production of levan (28.4 g/l) was achieved when sucrose and ammonium chloride were used as carbon and nitrogen sources, respectively, at 35℃ and an initial pH of 8.0. Some biomedical applications of levan like antitumor, antiparasitic, and antioxidant activities were investigated in vitro. The results revealed the ability of levan at different concentrations to decrease the viability of rhabdomyosarcoma and breast cancer cells compared with untreated cancer cells. Levan appeared also to have high antiparasitic activity against the promastigote of Leishmania tropica. Furthermore, levan had strong DPPH radical scavenging (antioxidant) activity. These findings suggest that levan produced by P. agglomerans ZMR7 can serve as a natural biopolymer candidate for the pharmaceutical and medical fields.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.849-852
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• 2001

The preparation, characterization and drug release behaviour of hydrocortisone(HC) loaded levan acetate microparticles were investigated. Hydrophobic levan acetate was prepared by chemical modification of hydrophilic levan and micro particles were made by dialysis method or solvent evaporation method. The morphology of levan acetate was observed by SEM and drug release profiles were investigated at pH 7.4 and pH 1.2. Newly synthesised levan acetate can be used for carrier of drugs.

• Journal of Microbiology and Biotechnology
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• v.14 no.4
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• pp.796-804
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• 2004

We found previously that dietary high fat caused obesity, and levan supplementation to the regular diet reduced adiposity and serum lipids. In the present study, we examined the effects of levan [high-molecular-mass $\beta$-(2,6)-linked fructose polymer] supplement on the development of obesity and lipid metabolism in rats fed with high-fat diet. Thus, to determine whether the dietary levan may have the anti-obesity and hypolipidemic effects, 4-wk-old Sprague Dawley male rats were fed with high-fat diet for 6 wk to induce obesity, and subsequently fed with 0, 1, 5, or 10% levan supplemented high-fat diets (w/w) for another 4 wk. For the comparison, a normal control group was fed with AIN-76A diet. Supplementation with levan resulted in a significant reduction of high-fat-induced body weight gain, white fat (i.e., epididymal, visceral, and peritoneal fat) development, adipocyte hypertrophy, and the development of hyperinsulinemia and hyperlipidemia in a dose-dependent manner. Serum triglyceride and free fatty acid levels were greatly reduced by levan supplementation. Serum total cholesterol level was reduced, whereas the HDL cholesterol level was increased by dietary levan. The expression of uncoupling protein (UCP) was increased by dietary high fat, and was further induced by levan supplementation. The mRNA level of UCP1, 2, and 3 in brown adipose tissue (BAT) and UCP3 in skeletal muscle was upregulated in rats fed with dietary levan. In conclusion, upregulated UCP mRNA expression may contribute to suppression of development of obesity through increased energy expenditure. The present results suggest that levan supplementation to the diet is beneficial in suppressing diet-induced obesity and hyperlipidemia.

• Food Science and Biotechnology
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• v.16 no.3
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• pp.482-484
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• 2007

To investigate production and hydrolysis of levan, the levansucrase enzymes from Zymomonas mobilis ATCC 10988 and Rahnella aquatilis ATCC 33071 were used. The optimum temperature of R. aquatilis levansucrase for levan formation was $37^{\circ}C$, whereas that of Z. mobilis was $4^{\circ}C$, under the experimental conditions. Both levansucrases also catalyzed the reverse levan hydrolysis reaction. Levan hydrolysis reactions from both levansucrases were temperature dependent; high temperature ($20^{\circ}C$) was more favorable than low temperature ($4^{\circ}C$) by 4 times. Fructose was the only product from hydrolysis reaction by both levansucrases, showing that both levansucrases mediated the hydrolysis reaction of exo-enzyme acting. In both enzymes, initial levan hydrolysis activity was almost accounted to 1% of initial levan formation activity. The results allow the estimation of the fructose release rate in enzyme processing conditions.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.6
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• pp.582-586
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• 2005

In this Study, we have attempted to determine the effects of dietary fructose polymers (fructan), high molecular-weight ${\beta}-(2,6)-linked$ levan, and low-molecular-weight ${\beta}-(2,1)-linked$ inulin, on two intestinal enzymes $({\beta}-glucuronidase\;and\;{\beta}-glucosidase)$. As a preliminary experiment, when intestinal microflora were cultured in anaerobic media harboring levan or its oligosaccharides, bacterial cell growth was observed in the levanoligosaccharide-supplemented media, but not in the levan-supplemented media, indicating that levan's size is important for the utilization by intestinal bacteria of levan as an energy Source. In our animal study, the intake of a levan-rich diet was determined to significantly attenuate the activity of the harmful enzyme $({\beta}-glucuronidase$, but d id not affect the activity of ${\beta}-glucosidase$.

• 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.

• Korean Journal of Community Nutrition
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• v.8 no.6
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• pp.986-992
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• 2003

This study was performed to investigate the effects of a levan diet on the body fat accumulation and serum lipid composition of 29 Korean women over a period of up to 12 weeks (n=13 for the control group, n=16 for the levan group). The subjects ate an uncooked diet (6 g) with 400$m\ell$ of tap water twice a day. The mean body weight and height measurements of the subjects (levan group) at the outset were 66.0$\pm$8.8kg and 156.7$\pm$5.3cm, respectively. The subjects showed a significant reduction in weight, body fat mass, anthropometric measurements and skinfold thickness during the experimental period. The waist hip ratio (WHR) was 0.88$\pm$0.03 at the outset, and fell to 0.82$\pm$0.05 after 4 weeks. The intake of levan was also influenced on the levels of serum Fe, leptin, lipoprotein lipase, HDL-cholesterol, LDL-cholesterol, and triglyceride. The serum glucose levels were within the normal range during the experimental period. The initial serum triglyceride level was 121mg/dl, but fell to 103mg/dl after 4 weeks of levan supplementation. The current study demonstrates that a levan diet is effective in controlling weight, body fat, HDL-cholesterol, LDL-cholesterol, and triglyceride levels.

• Journal of Microbiology and Biotechnology
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• v.14 no.6
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• pp.1232-1238
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• 2004

To investigate the production and characteristics of thermostable levan sucrase from Rahnella aquatilis ATCC 33071, the levan sucrase gene from R. aquatilis was cloned and expressed in Escherichia coli without induction system. Expression of levansucrase gene in E. coli had no notable or detrimental effect on the growth of host strain, and the recombinant levan sucrase exhibited levan synthesis activity. Levansucrase was secreted to the periplasm in E. coli, and addition of $0.5\%$ glycine yielded further secretion of levansucrase to the growth medium and resulted in an increase of total levansucrase activity. Furthermore, the cellular levansucrase was evaluated for the production of levan by using toluene­permeabilized whole-cells. The levansucrase was thermostable at $37^{\circ}C$. The molecular size oflevan was $1{\times}\;10^{6}$ Da, as determined by HPLC, and the degree of polymerization of levan varied with incubation temperatures: Low incubation temperature was preferable for the production of high-molecular size levan. The present study demonstrated that the mass production of levan and levan oligosaccharides can be achieved by glycine supplementation to the growth medium or by toluene­permeabilized whole-cells.

• Journal of Nutrition and Health
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• v.35 no.9
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• pp.912-918
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• 2002

In nature, two different types of fructose polymers (fructan) are generally found in dietary fibers; these are the fructose homopolymers levan, which is of high molecular weight and is $\beta$-(2,6)-linked, and inulin, which is of low molecular weight and is $\beta$-(2,1)-linked. The effects of levan and inulin on the intestinal physiology of rats were compared. Sprague Dawley rats were fed one of three diets for 3 weeks: a control diet, a basal diet containing 7% of levan, and a basal diet containing 7% of inulin. Cecal enlargement, together with the lowering of cecal pH, occurred in rats fed on the levan and inulin diets (p < 0.05). The levan and inulin diets resulted in a two-fold increase in the amount of short-chain fatty acids in the cecum, when compared to the control diet. The number of total microbes and of lactic acid-producing bacteria in the feces were higher in rats fed the fructan diets than those in rats fed control diet (p < 0.05). The levan diet also significantly increased the cecal $\alpha$-galactosidase activity by 3.8-fold, when compared to the control diet, indicating that levan stimulated the growth of Bifidobacteria in the cecum. These results show that the intake of levan and inulin stimulated the growth of lactic acid-producing bacteria in the cecum and thereby improved intestinal conditions in rats. (Korean J Nutrition 35(9) : 912~918,2002)