Abstract：
Bacterial cellulose (BC), a nanostructured material, is renowned for its excellent properties. However, its production by bacteria is costly due to low medium utilization and conversion rates. To enhance the yield of BC, this study aimed to increase BC yield through genetic modification, specifically by overexpressing bcsC and bcsD in Gluconacetobacter xylinus, and by developing a modified culture method to reduce medium viscosity by adding water during fermentation. As a result, BC yields of 5.4, 6.2, and 6.8 g/L were achieved from strains overexpressing genes bcsC, bcsD, and bcsCD, significantly surpassing the yield of 2.2 g/L from wild-type (WT) strains. In the modified culture, the BC yields of all four strains increased by >1 g/L with the addition of 20 mL of water during fermentation. Upon comparing the properties of BC, minimal differences were observed between the WT and pbcsC strains, as well as between the static and modified cultures. In contrast, BC produced by strains overexpressing bcsD had a denser microstructural network and exhibited demonstrated higher tensile strength and elongation-to-break. Compared to WT, BC from bcsD overexpressed strains also displayed enhanced crystallinity, higher degree of polymerization and improved thermal stability.
摘要：
细菌纤维素(BC),一种纳米结构的材料，以其优异的性能而闻名。然而,由于培养基利用率和转化率低，细菌生产的成本很高。为了提高BC的产量，这项研究旨在通过基因改造来提高BC产量，特别是通过在木葡糖醋杆菌中过表达bcsC和bcsD，并通过开发一种改良的培养方法，通过在发酵过程中添加水来降低培养基粘度。因此,从过表达基因bcsC的菌株获得5.4、6.2和6.8g/L的BC产量，bcsD,和bcsCD,显着超过野生型（WT）菌株2.2g/L的产量。在改良的文化中，在发酵过程中添加20mL水，所有四个菌株的BC产量增加>1g/L。在比较BC的属性后，在WT和pbcsC菌株之间观察到最小差异，以及静态和修改后的文化之间。相比之下,过表达bcsD的菌株产生的BC具有更致密的微结构网络，并表现出更高的拉伸强度和断裂伸长率。与WT相比，来自bcsD过表达菌株的BC也显示出增强的结晶度，较高的聚合度和改善的热稳定性。
