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

生物矿化生物体通过在矿物形成过程中筛选进化优化的生物聚合物，对其无机成分施加巨大的控制。这通常会导致多功能材料的出现，其中一些材料在使用“廉价”块状材料（碳酸钙、磷灰石或二氧化硅）的同时，显示出技术相关性能的优越组合，例如伴随的高硬度和韧性。虽然在过去，（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已经被许多研究者认识到，但从生物矿化原理中收集到的知识转移到胶结建筑材料的科学领域仍然难以捉摸。这种失败的原因是多方面的，从建筑材料固有的成本压力问题，到生物控制下矿化过程的不完整机制理解，以及胶凝材料（即混凝土）的复杂矿物学和凝结行为。这一建议旨在弥合这两个科学学科之间的差距。在一项合作努力中，我们建议研究由构成水泥混合物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产生的，它代表了一种生产复杂生物聚合物的成本效益手段，可以根据分子量分布、分支度和电荷密度进行基因定制。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）的相互作用将被探索，重点放在聚合物对多晶材料的特定多晶形态、单个晶体形态和结构的影响上。对于后一种混合材料，力学试验应作为获得力学性能改善的建筑材料的基准。从长远来看，这种受生物学启发的方法可能会为经济轻型建筑材料铺平道路，从而省去钢筋加固。

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.