Cellulose Production Of Acetobacter Xylinum Nust4.2

Bacterial cellulose (BC), a kind of biological material, is produced by some microorganisms. In comparison with natural cellulose, BC has high purities and other superior properties. Therefore BC has been one of the most active topics in the materials field.Nowadays domestic research on BC only rests on the level of laboratory, which lags behind far away from abroad where BC has been applied in many fields. In this paper, the culture medium of a cellulose-producing strain-Acetobacter xylinum NUST4.2 was optimized. 12.8L stirred-tank reactors were used for BC production. This strain's anti-variability and production performance in this reactor were studied. Structure and physical properties of BC synthesized under different culture conditions were studied. These investigations could establish foundation for the future industrialization. The main results were as follows:1. The optimum components were determined through homogeneous design and monofactorial experiment, including 25 g· L-1 glucose, 25 g· L-1 sucrose, 18 g· L-1 corn steep liquor, 2 g· L-1 (NH4)2SO4, 2 g· L-1 KH2PO4, 0.3 g· L-1 MgSO4 ·7H2O, 16 mg· L-1 FeSO4· 7H2O, 16 mg L-1 MnSO4 ·H2O, 4.8 mg·L-1 niacinamide and 0.48 mg·L-1 biotin. The BC production was 8.86 g·L-1.2. Acetobacter xylinum NUST4.2's productivity was examined by fed-batch and repeated fed-batch culture method in the 12.8L stirred-tank reactor. Using repeated fed-batch culture method, Acetobacter xylinum NUST4.2 had better activity and higher cellulose productivity.3. The physical and chemical properties of BC were proved by X-ray diffraction (XRD), Fourier transform-infrared spectrum (FT-IR) and transmission electron microscopic (TEM). The result of tests was as follows: the product was I type cellulose, and the proportion of I a was 80% or so. Crystallinity index was between 70%-80%. BC diameter was among 10nm-80nm. Young modulus, tensile strength, thermal stability and water-absorption capacity were tested. These results showed that BC produced by Acetobacter xylinum NUST4.2 had in-twisting network structure of many fiber ribbons. Furthermore the BC had higher crystallinity, higher Youngs modulus, stronger water absorption and better thermal stability, which indicated that BC was a superior biomaterial.