Studies on Regulation and Formation Process of Higher-Order Structure of Bacterial Cellulose

Crysta Lis of native cellulose are composites of two allomorphs，celluloses I_&lt；alpha&gt；and I_&lt；beta&gt；.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.About10-16cellulose 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_&lt；alpha&gt；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_&lt；alpha&gt；.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 4óC，and ribbons of cellulose I at 28ºC.The crystalline structure and higer-order structure of cellulose are controlled by changing the culture temperature.3.The reflections corresponding to I_&lt；alpha&gt；were obtained by selected-area electron diffraction of one ribbon assembry.But the distribution of I_&lt；alpha&gt；and I_&lt；beta&gt；is not determined yet.4.From these results we have proposed the crystallization mechanism for celluloses I_&lt；alpha&gt；and I_&lt；beta&gt；。

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>.