• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.356-359
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• 2000

A two-stage fed-batch fermentation was carried out to increase xylitol productivity by Candida tropicalis. The first stage for cell growth was performed in the pH-stat and continuous fed-batch modes. The higher cell growth and lower ethanol production obtained in the fed-batch mode where the growth medium was fed when pH of culture broth increased over 5.7. And also the effect of oxygen transfer on xylitol production was investigated by changing agitation speed under 0.5 vvm of aeration. The maximum xylitol productivity and yield were obtained at 500 rpm of agitation.

• KSBB Journal
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• v.17 no.1
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• pp.93-99
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• 2002

Two-stage fed-batch culture of Candide tropicalis that was designated primarily to cultivate the cell in the glucose medium (1st stage) and then produced the xylitol from xylose medium (2nd stage) was developed to improve a xylitol yield and productivity. In the growth stage, glucose was automatically supplied to the fermentor by pH-stat mode when the pH was up 5.7, When a feeding medium was added in order to reach the glucose and yeast extract concentrations up to 100 and 40 g/L, respectively, a high cell concentration and a relatively low ethanol concentration were obtained in 18.5 h culture. In the production stage, initial xylose concentration of 150 g/L was the most favorable for obtaining the final xylitol concentration and productivity. The addition of mineral salts was also enhanced a xylitol production. But the aeration rate was not significantly affected a xylitol production. When the addition of 16 g yeast extract and 232.5 g xylose powder at the production stage was used, xylitol yield and productivity were significantly increased. With these conditions, xylitol concentration, yield and productivity of 108.9 g/L, 74%) and 3.3 g/L·h, respectively, were obtained in a final volume of 1.58 L. The further addition of 16 g yeast extract and 232.5 g xylose powder increased the working volume partly (1.67 L) and resulted in a relatively high xylitol concentration, yield and productivity of 193 g/L, 70% and 3.6 g/L·h, respectively.

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.4
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• pp.632-638
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• 2007

The purpose of this study was to investigate the effect of xylitol chewing gums on mutans streptococci (MS) counts in saliva. Sixty two children 6 to 11 years old were randomly assigned into one of three groups. Stimulated saliva specimens were plated in duplicate on conventional selective culture (mitis salivarius kanamycin bacitracin agar) for mutans streptococci. Polymerase chain reaction (PCR) amplication was performed to identify MS. After the 4-month period a significant decrease of the MS counts occurred in the group B (two gum 3 times a day; P < 0.05) but not in group A (one gum 3 times a day) and control group (didn't receive xylitol gum). According to qualitative evaluations, xylitol use did reduce the levels of MS in mixed dentition children. It has been suggested that a daily intake of 2 tablet for 3 times a day (about 10g) is needed in order to obtain a clinical anticariogenic effect.

• International Journal of Oral Biology
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• v.38 no.3
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• pp.127-134
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• 2013

Xylitol is a sugar alcohol with a variety of functions including bactericidal and anticariogenic effects. However, the cellular mechanisms underlying the role of xylitol in bone metabolism are not yet clarified. In our present study, we exploited the physiological role of xylitol on osteoclast differentiation in a co-culture system of osteoblastic and RAW 264.7 cells. Xylitol treatment of these co-cultures reduced the number of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells induced by 10 nM $1{\alpha},25(OH)_2D_3$ in a dose-dependent manner. A cell viability test revealed no marked cellular damage by up to 100 mM of xylitol. Exposure of osteoblastic cells to xylitol decreased RANKL, but not OPG, mRNA expression in the presence of $10^{-8}M$ $1{\alpha},25(OH)_2D_3$ in a dose-dependent manner. Furthermore, bone resorption activity, assessed on bone slices in the coculture system, was found to be dramatically decreased with increasing xylitol concentrations. RANKL and OPG proteins were assayed by ELISA and the soluble RANKL (sRANKL) concentration was decreased with an increased xylitol concentration. In contrast, OPG was unaltered by any xylitol concentration in this assay. These results indicate that xylitol inhibits $1{\alpha},25(OH)_2D_3$-induced osteoclastogenesis by reducing the sRANKL/OPG expression ratio in osteoblastic cells.

• Journal of Microbiology and Biotechnology
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• v.11 no.4
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• pp.564-569
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• 2001

This study was carried out in order to investigate the characteristics of xylitol fermentation by a xylitol dehydrogenase defective mutant PXM-4 of P stipitis CBS 5776 and to determime optimum conditions for the high yield ofxylitol production from xylose. Gluconic acid was selected as a co substrate for the xylitol fermentation, since gluconic acid neither blocked xylose transport nor repressed xylose reductase expression. An increase of gluconic acid concentration reduced the rates of xylitol production and cell growth by decreasing medium pH, and the optimal concentration of gluconic acid was determined to be 20 gll with approximately 100% xylitol conversion yield. A fed-batch cell culture resulted in a 44.8 g/l xylitol concentration with 100% yield, based on the amount of xylose consumed.

• International Journal of Oral Biology
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• v.38 no.4
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• pp.175-180
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• 2013

Xylitol is a five-carbon sugar alcohol that reduces the incidence of caries by inhibiting the growth of oral streptococci, including Streptococcus mutans. Since xylitol is transported via the fructose phosphotransferase system, we hypothesized that it could also affect the growth of other oral bacteria strains. We tested the effects of xylitol against non-periodontopathogenic oral bacteria frequently found in healthy subjects as well as periodontopathogens including Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia. With 5% xylitol, Streptococcus vestibularis and Gemella morbillorum showed marked growth inhibition. With 10% xylitol, all of the tested periodontopathogens and Actinomyces naeslundii showed marked growth inhibition, whereas the growth inhibition of Neisseria mucosa, Neisseria sicca and Veillonella parvula was mild only. Xylitol is a widely used sweetener and the concentration used in our experiment is easily achieved in the oral cavity. If xylitol reduces the growth of periodontopathogens more preferentially, it could also reduce the prevalence of these pathogens and have clinical utility in the prevention or treatment of periodontal disease.

• Applied Biological Chemistry
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• v.39 no.3
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• pp.172-176
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• 1996

Effect of culture conditions such as pH, temperature, agitation speed and oxygen transfer rate on xylitol production from xylose by Candide parapsilosis ATCC 21019 mutant was investigated in a jar fermentor. The initial concentration of xylosr was fixed at 50 g/l in this experiment. When pH was increased, cell growth and xylose consumption rate were increased, but maximum xylitol production was shown in the range of pH 4.5 and 5.5 with a yield of 0.68 g/g-xylose. The optimal temperature for xylitol production was determined to be $30^{\circ}C$. Considering the importance of dissolved oxygen tension, for xylitol production, the effect of oxygen transfer rate coefficient $(k_La)$ on fermentation parameters was carefully evaluated in the range of $20{\sim}85\;hr{-1}\;of\;k_La$ (corresponding to $100{\sim}300$rpm of agitation speed). The xylitol production was maximized at $30\;hr^{-1}\;of\;k_La$(150 rpm). A higher oxygen transfer rate supported better cell growth with lower xylitol yield. It was determined that maximum xylitol concentration, xylitol yield and productivity was 35.8 g/l, 71.6% and $0.58\;g/l{\sim}hr^{-1}$, respectively, at $30\;hr^{-1}\;of\;k_La$ In order to further increase xylitol productivity, ferementation using the concentrated biomass(20 g/l) was carried out at the conditions of pH 4.5, $30^{\circ}C$ and $30\;hr\;1$ of oxygen transfer rate. The final xylitol concentration of 40 g/l was obtained at 18 hours of culture time. From this result, it was calculated that xylitol yield was 80ft on the basis of xylose consumption and volumetric productivity was $2.22\;g/l{\sim}hr$ which was increased by $3{\sim}4$ fold compared with $0.5{\sim}0.7\;g/l-hr$ obtained in a normal fermentation condition.

• Journal of dental hygiene science
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• v.11 no.5
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• pp.411-416
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• 2011

Streptococcus mutans (S. mutans) is the major causative bacteria in dental caries. Xylitol is effective anticarious natural sugar substitute by inhibiting the virulence of S. mutans. However, long-term xylitol consumption leads to the emergence of the xylitol-resistant (XR) strains which means xylitol is no more inhibited their growth. We therefore confirmed the general characteristics and the virulence factors of the xylitol-sensitive (XS) and XR S. mutans for different concentrations of xylitol. S. mutans KCTC 3065 was maintained in TYE medium containing 0.4% glucose with 1% xylitol during 30 days at $37^{\circ}C$, 10% $CO_2$ to form XR strain. The strains were transferred to new medium every 24 hr and the same procedures without xylitol were repeated for the formation of XS S. mutans. Both XS and XR were cultured in different concentrations of xylitol (0%, 0.1% and 1%) then, cell growth, acid production and mRNA expression of gtf genes were analyzed. Xylitol reduced the cell growth of XS S. mutans in dose-dependent manner, but not reduced that of XR. Xylitol inhibited acid production of XS in dose-dependent manner, but not inhibited that of XR. Xylitol reduced the gtfB and gtfD mRNA expression of XS S. mutans which genes synthesized soluble and insoluble extracellular polysaccharides, but not reduced that of XR. These results indicate that the virulence of XR S. mutans is different characters of XS strains, which suggests XR strains may have different cariogenicity of XS strains. Further study is needed to explain the mechanism related to extracellular polysaccharide in the XR strains.

• Journal of Life Science
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• v.27 no.12
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• pp.1403-1409
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• 2017

In this study, the xylitol dehydrogenase (XYL2) gene was expressed in Saccharomyces cerevisiae as a host cell for ease of use in the degradation of lignocellulosic biomass (xylose). To select suitable expression systems for the S.XYL2 gene from S. cerevisiae and the P.XYL2 gene from Pichia stipitis, $pGMF{\alpha}-S.XYL2$, $pGMF{\alpha}-P.XYL2$, $pAMF{\alpha}-S.XYL2$ and $pAMF{\alpha}-P.XYL2$ plasmids with the GAL10 promoter and ADH1 promoter, respectively, were constructed. The mating factor ${\alpha}$ ($MF{\alpha}$) signal sequence was also connected to each promoter to allow secretion. Each plasmid was transformed into S. cerevisiae $SEY2102{\Delta}trp1$ strain and the xylitol dehydrogenase activity was investigated. The GAL10 promoter proved more suitable than the ADH1 promoter for expression of the XYL2 gene, and the xylitol dehydrogenase activity from P. stipitis was twice that from S. cerevisiae. The xylitol dehydrogenase showed $NAD^+$-dependent activity and about 77% of the recombinant xylitol dehydrogenase was secreted into the periplasmic space of the $SEY2102{\Delta}trp1/pGMF{\alpha}-P.XYL2$ strain. The xylitol dehydrogenase activity was increased by up to 41% when a glucose/xylose mixture was supplied as a carbon source, rather than glucose alone. The expression system and culture conditions optimized in this study resulted in large amounts of xylitol dehydrogenase using S. cerevisiae as the host strain, indicating the potential of this expression system for use in bioethanol production and industrial applications.

• KSBB Journal
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• v.15 no.1
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• pp.35-41
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• 2000

We tried to prepare encapsulated whole cell cyclodextrin glucanotransferase(CGTase) in order to produce glycosyl-xylitol using xylitol as glucosyl acceptor. The organic nitrogen source was more effective for the production of CGTase from Bacillus macerans IFO 3490 than the inorganic one. Most of the CGTase which had been produced during cultivation was excreted to the growth medium. B. macerans cells inocculated in the capsule failed to grow to the high cell density. Adsorbents such as activated charcoal, Sephadex and Amberite resins could not adsorb efficiently the CGTase from the broth solution. We obtained successfully the encapsulated whole cell CGTase by immobilizing the concentrated broth solution in the calcium alginate capsules. The encapsulated whole cell CGTase carried out the transglycosylation reaction which converts xylitol into glucosyl-xylitol using dextrin as glucosyl donor.