1996 Fiscal Year Final Research Report Summary
Studies on Regulation and Formation Process of Higher-Order Structure of Bacterial Cellulose
| Project/Area Number |
07660436
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
生物資源科学
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
HIRAI Asako Kyoto University, Institute for Chemical Research, Asssociate Instructor, 化学研究所, 教務職員 (20156623)
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| Co-Investigator(Kenkyū-buntansha) |
TSUJI Masaki Kyoto University, Institute for Chemical Research, Asssociate Professor, 化学研究所, 助教授 (60172003)
HORII Fumitaka Kyoto University, Institute for Chemical Research, Professor, 化学研究所, 教授 (70124758)
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| Project Period (FY) |
1995 – 1996
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| Keywords | bacterial cellulose / cellulose I_<alpha> / cellulose I_<beta> / microfibril / CMC / transmission electron microscopy / electron diffraction / high resolution solid state NMR |
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| Research Abstract |
Crystaリs of native cellulose are composites of two allomorphs, celluloses I_<alpha> and I_<beta>.In this paper we have examined the crystallization process and formation process of higher-order structure of bacterial cellulose. The results obtained are as given bellow :
1.About 10-16 cellulose chains which form a sub-elementary fibril are extruded out from the Acetobacter xylinum cell and aggregate with each other to form smaller-size microfibrils. Such microfibrils further aggregate into a larger-size microfibril as ribbon assembly. Polymeric additives such as carboxymethyl cellulose sodium salt (CMC) and xyloglucan (XG) induced the formation of thinner, splayd microfibrils in stead of the ribbon assembly and also reduced the mass fraction of I_<alpha> Among polymeric additives CMC was the most effecive and there were recognized optimal DP and DS for addition of them. The average size of microfibril reduced with increasing concentration of CMC.The reduction of the size was highly correlated with the decrease in mass fraction of I_<alpha>.
2.Two different colony types, rough and smooth colonies, were isolated from A.xylinum. The smooth colony produced the band material composed of cellulose II at 4ﾟC,and ribbons of cellulose I at 28ﾟC.The crystalline structure and higer-order structure of cellulose are controlled by changing the culture temperature.
3.The reflections corresponding to I_<alpha> were obtained by selected-area electron diffraction of one ribbon assembly. But the distribution of I_<alpha> and I_<beta> is not determined yet.
4.From these results we have proposed the crystallization mechanism for celluloses I_<alpha> and I_<beta>.
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