Zhou Ling-Li, Sun Dong-Ping, Wu Qing-Hang, Yang Jia-Zhi, Yang Shu-Lin
Bioengineering Department, Institute of Chemical Engineering, Nanjing University of Science & Technology, Nanjing 210094, China.
Wei Sheng Wu Xue Bao. 2007 Oct;47(5):914-7.
Acetobacter xylinum NUST4.2 has been applied in the studies to examine the production, structure and thermal property of bacterial cellulose (BC) produced in stationary culture and in the stirred tank reactor. These differences are as follows: BC yield reached 7.5 g/L in stationary culture for 6 days and its productivity was 0.052 g/L/h. BC production reached 3.13 g/L in the stirred tank reactor for 72h and its productivity was 0.043 g/L/h. SEM showed that there was almost no difference between network structure built of entangled cellulose ribbons produced in static culture and in the reactor. But the cellulose ribbons produced in static culture were a much more entangled and denser network with curved and overlapping cellulose ribbons in comparison with that one produced in the stirred tank reactor. Also the thickness of the cellulose ribbons seems to differ between the two BC samples, with the one from static culture distinguished by the slightly thinner ribbons. FT-IR revealed that there was no effect of stirring on the chemical structure of BC, but intermolecular hydrogen bond of cellulose was weakened. Furthermore, BC synthesized in static culture displayed I(alpha)-rich cellulose. XRD results indicated that no remarkable change in the cellulose crystallographic form of the BC samples. Nevertheless, BC produced in static culture was characterized by a higher crystallinity, higher I(alpha) content and higher crystalline size than cellulose that was produced in the reactor. All of these results revealed that stirring in the reactor interfere strongly in the process of nascent microfibrils crystallization, favoring the formation of smaller size microfibrils and increased I(beta), the more stable allomorph. Compared with cotton cellulose, the changes of thermal decomposition behavior in the BC samples were that BC produced in static culture displayed better thermal stability, but BC produced in the stirred reactor displayed better flame retarding.
木醋杆菌NUST4.2已应用于相关研究，以考察在静置培养和搅拌罐反应器中生产的细菌纤维素（BC）的产量、结构和热性能。这些差异如下：在静置培养6天时，BC产量达到7.5 g/L，其生产率为0.052 g/L/h。在搅拌罐反应器中培养72小时时，BC产量达到3.13 g/L，其生产率为0.043 g/L/h。扫描电子显微镜（SEM）显示，静置培养和反应器中由缠结的纤维素带构建的网络结构几乎没有差异。但与搅拌罐反应器中产生的纤维素带相比，静置培养中产生的纤维素带形成的网络更加缠结和致密，纤维素带弯曲且相互重叠。此外，两个BC样品中纤维素带的厚度似乎也有所不同，静置培养得到的样品中纤维素带略薄。傅里叶变换红外光谱（FT-IR）显示，搅拌对BC的化学结构没有影响，但纤维素的分子间氢键被削弱。此外，静置培养合成的BC显示富含I(α)型纤维素。X射线衍射（XRD）结果表明，BC样品的纤维素晶体形式没有显著变化。然而，与反应器中生产的纤维素相比，静置培养生产的BC具有更高的结晶度、更高的I(α)含量和更大的晶体尺寸。所有这些结果表明，反应器中的搅拌强烈干扰了新生微纤丝的结晶过程，有利于形成尺寸更小的微纤丝并增加更稳定的同质异形体I(β)。与棉纤维素相比，BC样品热分解行为的变化是，静置培养生产的BC具有更好的热稳定性，但搅拌反应器中生产的BC具有更好的阻燃性。
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