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，并通过结合不同的化合物，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，它的抗压强度得到增强，但也出现了新的特性，例如木质素作为密封剂保护植物免受水侵入。一些特殊的细菌也能组装纤维素。然而，它们缺乏吸收其他化合物的能力。随着合成生物学的兴起，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，成为可能。未经改性的细菌纤维素，已经是一种非凡的聚合物，今天被广泛应用，例如在医学上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和改进现有产品，可以通过改变细胞生长介质的组成或通过合成后的化学修饰对其进行生物修饰。这两种方法都会带来相当大的工作量。不管改性的可能性如何，细菌纤维素仍然是无弹性的。超过一定的力阈值，单个纤维素纤维失去稳定性，纤维素纤维分解成它们的组成部分。弹性蛋白样多肽（Elastin-like polypeptides, ELPs）是一种具有弹性和环境响应性的聚合物，非常适合作为细菌纤维素的补充材料，以克服其弹性的局限性。它们的拉伸和再折叠能力不会改变纤维素的高抗拉强度，从而提高共聚物的延展性。此外，ELP支架结构可以以特定位点的方式结合额外的蛋白质，以增加额外的功能，如生物传感、药物传递或生物功能化。提出的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。通过将产纤维素菌株Komagataeibacter rhaeticus与产蛋白质菌株如酿酒酵母（Saccharomyces cerevisiae）共培养，创造了一种很有前途的新型复合材料“Cellulastin”。这两种生物分泌不同的生物聚合物，理想地融合成一种具有巨大潜力的新型有前途的复合材料。特别是，elp对环境刺激的反应可以被用来提供独特的性能。这种方法将使智能共聚物的合成成为可能，这些共聚物由高度可调的、可持续的、交织的纤维素和elp网络组成。

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.