Tuning engineered microbial co-cultures to produce novel and functionalisable cellulose-elastin composites (Cellulastin)

植物组装世界上最丰富的生物聚合物，纤维素，并通过掺入不同的化合物，如木质素，果胶或半纤维素，将其编织成机械坚固的复合材料。因此，它的抗压强度增强，但也出现了新的特性，例如木质素作为密封剂，以保护植物免受水分入侵。一些特殊的细菌也能够组装纤维素。然而，它们缺乏掺入额外化合物的能力。随着合成生物学的兴起，有可能设计这些细菌来模仿植物组装纤维素基复合材料的方式，并创造出增强的、可持续的生物聚合物。未经改性的细菌纤维素已经是一种非凡的聚合物，如今被广泛应用，例如在医学中作为皮肤替代品或在食品工业中作为填充剂。为了扩大其应用范围并改进现有产品，可以通过改变细胞生长培养基组成或通过合成后化学修饰对其进行生物修饰。这两种方法都造成了相当大的工作量。不管改性的可能性，细菌纤维素保持非弹性。在一定的力阈值以上，单个纤维素纤维失去其稳定性，并且纤维素纤维分解成其组分。弹性蛋白样多肽（ELP），弹性和环境响应性聚合物，似乎非常适合补充细菌纤维素，以克服弹性的限制。它们在不改变纤维素的高拉伸强度的情况下拉伸和再折叠的能力可以改善共聚物的延展性。此外，ELP支架结构可以以位点特异性方式掺入额外的蛋白质以增加额外的特征，例如生物传感、药物递送或生物功能化。拟议项目挑战目前的细菌纤维素生产，旨在交联细菌纤维素网内的ELP。通过将纤维素生产菌Komagataeibacter rhaeticus与蛋白质分泌菌如酿酒酵母（Saccharomyces cerevisiae）共培养，产生了一种有前途的新型复合材料“纤维素”。这两种生物都分泌不同的生物聚合物，理想地融合成具有巨大潜力的新的有前途的复合材料。特别地，ELP对环境刺激的响应可用于提供独特的性质。这种方法将使从头合成的智能共聚物组成的高度可调的，可持续的，交织的网络纤维素和ELP。

Plants assemble the world’s most abundant biopolymer, cellulose, and weave it into a mechanically robust composite material by incorporation of different compounds, such as lignin, pectin or hemicellulose. Consequently, its compressive strength is enhanced, but also new characteristics emerge, e.g. lignin acts as a sealant to protect plants from water intrusion. Some specialised bacteria are also capable of assembling cellulose. However, they lack the ability to incorporate additional compounds. With the rise of synthetic biology it became possible to engineer these bacteria to mimic the way plants assemble cellulose-based composites and create enhanced, sustainable biopolymers. Unmodified bacterial cellulose, already an extraordinary polymer, is used in a broad range of applications today, e.g. in medicine as skin replacement or in food industry as bulking agent. To extend its application range and improve already existing products, it can be biologically modified by altering the cell growth medium composition or by post-synthesis chemical modifications. Both methods impose a considerable workload. Regardless of the modification possibilities, bacterial cellulose remains inelastic. Above a certain force threshold, single cellulose fibres lose their stability, and the cellulose fibers disintegrate into their components. Elastin-like polypeptides (ELPs), elastic and environment-responsive polymers, appear to be highly suited to complement bacterial cellulose to overcome the limitation of elasticity. Their capability to stretch and refold without altering the high tensile strength of cellulose could improve the ductility of the copolymer. Moreover, an ELP scaffolding structure can incorporate additional proteins in a site-specific manner to add additional features, such as biosensing, drug delivery, or biofunctionalisation. The proposed project challenges the current bacterial cellulose production and aims to crosslink ELPs within the bacterial cellulose mesh. By co-cultivating the cellulose producing strain Komagataeibacter rhaeticus with a protein secreting strain, e.g. Saccharomyces cerevisiae, a promising new composite material, “Cellulastin”, is created. Both organisms secrete different biopolymers which ideally fuse into a new and promising composite material with immense potential. Especially, the response to environmental stimuli of ELPs can be utilised to provide unique properties. This approach will enable the de novo synthesis of smart copolymers consisting of highly tunable, sustainable, and interwoven networks of cellulose and ELPs.