• Applied Biological Chemistry
• /
• v.41 no.4
• /
• pp.209-212
• /
• 1998

Methylan, a polysaccharide produced from Methylobacterium organophilum, was chemically modified by adding diethylaminoethyl (DEAE) group to the backbone of methylan. The structure of DEAE-methylan was determined by measuring its nitrogen content obtained from an elemental analysis. From the analysis of mass spectrum, the DEAE group in DEAE-methylan was also confirmed by determining diethylaminoethene as a separate form of DEAE. Mercury adsorption of DEAE-methylan was higher than that of native methylan. This fact was valid for a variety of pH, reaction times, metal concentrations, and polysaccharide concentrations. In particular, native methylan and DEAE-methylan adsorbed 16% (w/w) and 18% (w/w) for mercury after 30 min at pH 7, respectively. The increase in mercury adsorption of DEAE-methylan may be resulted from mercury adsorption by the lone pair electron of nitrogen atom in DEAE group.

• Applied Biological Chemistry
• /
• v.38 no.3
• /
• pp.191-195
• /
• 1995

Production of a high viscosity exoploysaccharide, methylan, by Methylobacterium organophilum from methanol was carried out in fed-batch cultures and the rheological properties of methylan fermentation broth were studied. Bacterial biomass showed little influence on viscosity, but the accumulation of methylan caused the increase of viscosity. With proceeding fermention, the viscosity at the same concentration of methylan was significantly increased and methylan solution showed slightly higher pseudoplasticity. The composition changes of methylan were investigated at various fermentation times. Contents of total sugar, reducing sugar and methylan were decreased but contents of acids(pyruvic acid, uronic acid and acetic acid) were increased with the culture time. It was considered that the increased content of acids resulted in the increase of the hyrodynamic domain in the solution due to charge repulsion. Consequently, the solution viscosity increased in propotion to the acids contents of methylan. Cell growth and methylan production were severely decreased by the limitation of dissolved oxygen. However, the cellular activity for methylan production was almost constant regardless of the level of dissolved oxygen. As a result, the high speed of agitation increased the methylan production, the specific production rate of methylan, and the methylan yield of the cell.

• Korean Journal of Food Science and Technology
• /
• v.29 no.6
• /
• pp.1151-1157
• /
• 1997

The chemical identities of purified polysaccharide, methylan, were analyzed by various chemical methods. The polysaccharide contained 79%(w/w) sugar, 6% protein, and 16% organic acids such as uronic acid, pyruvic acid, and acetic acid. With proceeding fermentation, the acids content in methylan increased from 10% at 34 hr to 17% at 72 hr, and the viscosity of methylan in the same concentration also increased. The correlation between viscosity and acid content in methylan was studied using chemically or biologically modified methylan. Methylan with a high content of pyruvic acid exhibited a high apparent and an intrinsic ·viscosity. When the pyruvic acid content of methylan with the same content of uronic acid was increased 1%, apparent viscosity and intrinsic viscosity increased 290 cp and 6 dL/g, respectively. Methylan with a high content of uronic acid exhibited a high apparent and an intrinsic viscosity. When the uronic acid content of methylan with the same content of pyruvic acid was increased 1%, apparent viscosity and intrinsic viscosity increased 85 cp and 1.5 dL/g, respectively. It was found that the increased viscosity of methylan resulted from the increased content of organic acids in methylan, and pyruvic acid was more an important factor contributed to the increase of methylan viscosity than uronic acid.

• Microbiology and Biotechnology Letters
• /
• v.26 no.3
• /
• pp.244-249
• /
• 1998

An extracellular polysaccharide, methylan, was produced under the specific conditions by Methylobacterium organophilum from methanol. The specific growth rate of cells was approximately constant regardless of C/N ratio and the specific product yield was maximum at a C/N ratio of 30. Methylan production was suppressed by the deficiency of mineral ions such as Mn$^{++}$ or Fe$^{++}$ ion. The optimal pH for cell growth and methylan production was 7. Whereas the optimal temperature for cell growth was found to be 37$^{\circ}C$, that for methylan production was 3$0^{\circ}C$. The methanol concentration above 4% completely inhibited the cell growth. The initial methanol concentration for the maximal production of methylan was 0.5% (v/v) and above this concentration, methylan production was markedly inhibited. To overcome the substrate toxicity and inhibition for both cell growth and methylan production, a fed-bach culture of intermittent feeding within 5 g/l methanol was conducted under the optimal culture condition. Methylan production of was stimulated by nitrogen limitation and methylan was accumulated up to 8.7 g/1 and cell mass also increased up to 12.4 g/l.

• The Microorganisms and Industry
• /
• v.18 no.1
• /
• pp.59-63
• /
• 1992

값이 저렴한 메탈올로부터 새로운 고점도성 생물고분자인 다당류의 생산과 활용은 산업적으로도 매우 흥미있는 분야이다. 본고에서는 최근 본 연구실에서 개발한 메탄올 자화세균(facultative methylotroph)인 Methylobacterium organophilum이 생산하는 신규의 고점성 다당류인 메틸란(methylan)의 생산 및 그 특성과 응용에 관하여 고찰하고자 한다.

• KSBB Journal
• /
• v.10 no.2
• /
• pp.170-175
• /
• 1995

The effect of nitrogen source on production of a high viscosity exopolysaccharide, methylan, from methanol by Mentylobacterium organophilum was investigated in fed-batch culture. During the fermentation, cells continued to grow even after the nitrogen source added to the medium was depleted and methylan production was stimulated under the condition which ammonium ion was depleted. Cell growth increased proportionally to the initial concentration of ammonium ion in the medium, but methylan production was significantly inhibited at the high concentration of ammonium ion. As the initial concentration of ammonium ion increased, the specific growth rate, the specific product formation rate and the specific substrate consumption rate decreased due to the inhibitory effect of excess ammonium ions. In order to reduce the inhibitory effect by high concentration of ammonium ion. The control of ammonium ion concentration within the desired level(usually $0.45g/\ell$) was necessary. When ammonium ion concentration was maintained below $0.15g/\ell$ by exponential feeding, methylan production could be increased up to $12.5g/\ell$.

• KSBB Journal
• /
• v.10 no.2
• /
• pp.176-182
• /
• 1995

The environmental and physiological factors affecting the production of exopolysaccharide (Methylan) and Poly-${\beta}$-hydroxybutyrate(PHB) by Methylobacterium organophilum were investigated. The maximum PHB content was obtained at $38^{\circ}C$ whereas maximum polysaccharide concentration was $3.54g/\ell$ at $30^{\circ}C$. Optimum pH was pH 7-8 for PHB production and pH 6-7 for polysaccharide production, respectively. Under the condition of $Mo^{2+}, Mg^{2+} or Mn^{2+}$ limitation with nitrogenlimitation, the PHB accumulation was increased, whereas the polysaccharide production was decreased as compared with that of solenitrogenlimitation. Under the condition of sole K+ limitation, cell growth was significantly inhibited and no polysaccharide was produced. However, the PHB content was as high as 60% of dry cell weight. Effect of C/N ratios (methanol/ammonium) in the feeding solution was examined for the simultaneous production of polysaccharide and PHB. The higher ratio of C/N showed the lower cell growth, higher content of PHB in cells, and higher yield of polysaccharide.