Tailoring cementitious materials with genetically, engineered microbial exopolysaccharides, a biologically inspired approach towards high-performance construction materials

生物矿化生物通过在矿物形成过程中释放进化优化的生物聚合物，对其无机成分施加巨大的控制。这往往导致多功能材料的出现，其中一些材料表现出与技术相关的性能的卓越组合，例如伴随的高硬度和高韧性，同时使用“廉价”的块状材料(CaCO3、磷灰石或二氧化硅)。尽管在过去，许多研究人员已经认识到(承重)生物矿物(如骨、牙齿、贝壳)和高性能建筑材料之间的潜在技术联系，但从生物矿化原理收集的知识转移到水泥建筑材料科学领域仍然难以捉摸。失败的原因是多方面的，从建筑材料固有的成本压力问题，到对生物控制下的矿化过程的不完全机械理解，以及胶凝材料(即混凝土)的复杂矿物学和凝结性能。这项建议旨在弥合这两个科学学科之间的差距。在一项合作工作中，我们建议研究由组成水泥混合物的组成成分的多糖和主要矿物相组成的杂化材料的形成。微生物胞外多糖是在悬浮细胞培养中生产的，这是一种成本效益高的方法，可以生产复杂的生物聚合物，可以根据分子量分布、支化度和电荷密度进行遗传定制。应探讨这些聚合物与与建筑材料相关的无机相(碳酸钙、硫酸盐和水合铝酸钙)的相互作用，重点放在聚合物对多晶材料的特定晶型、单个晶体形态和织构的影响。对于后一种混合材料，力学测试应该作为基准，以获得显示出更好的力学性能的建筑材料。从长远来看，这种受生物启发的方法可能会为经济的轻型建筑材料铺平道路，这种材料将不需要钢筋。

Biomineralizing organisms exert vast control on their inorganic components by secerning evolutionary optimized biopolymers during mineral formation. This often leads to multifunctional materials, some of which show superior combinations of technically relevant properties, such as a concomitant high hardness and toughness, while employing “inexpensive” bulk materials (CaCO3, apatite or silica). Although in the past, the potential technological link between (load-bearing) biominerals (e.g. bone, teeth, shells) and high-performance construction materials had been realized by numerous investigators, the knowledge transfer gleaned from biological mineralization principles into the scientific field of cementitious construction materials as yet has remained elusive. The reasons for this failure are manyfold, ranging from the problem of cost pressure, which is immanent to construction materials, to the incomplete mechanistic understanding of mineralisation processes under biological control as well as the complex mineralogy and setting behaviour of cementitious materials (i.e. concrete).This proposal aims at bridging the gap between the two scientific disciplines. In a collaborative effort we propose to study the formation of hybrid materials that are composed of polysaccharides and major mineral phases that constitute components of cement mixtures. Microbial exopolysaccharides are being produced in suspension cell cultures, which represents a cost-efficient means to produce complex biopolymers that can be genetically tailored in terms of molecular weight distribution, branching degree and charge density. The interactions of these polymers with inorganic phases relevant to construction materials (calcium carbonate, sulphate, and calcium aluminate hydrate) shall be explored with the focus laid upon the polymers’ influence exerted on the particular polymorph, individual crystal morphology and the texture of polycrystalline materials. For the latter hybrid materials, mechanical tests should serve as benchmark for deriving construction materials that show improved mechanical properties. As a long-term perspective, this biologically inspired approach might pave the way towards economic light-construction materials that will dispense with steel reinforcements.