The process of microbially induced carbonate precipitation (MICP) is known to effectively improve engineering properties of building materials and so does silk fibroin (SF). Thus, in this study, an attempt was taken to see the improvement in sand, that is, basic building material coupled with MICP and SF. Urease producing Bacillus megaterium was utilized for MICP in Nutri-Calci medium. To improve the strength of SF itself in bacterial solution, it was cross-linked with genipin at the optimized concentration of 3.12 mg/mL. The Fourier transform infrared (FTIR) spectra confirmed the crosslinking of SF with genipin in bacterial solution. In order to understand how such cross-linking can improve engineering properties, sand moulds of 50 mm³ dimension were prepared that resulted in 35% and 55% more compressive strength than the one prepared with bacterial solution with SF and bacterial solution only, respectively with higher calcite content in former one. The FTIR, SEM, x-ray powder diffraction spectrometry and x-ray photoelectron spectroscopy analyses confirmed higher biomineral precipitation in bacterial solution coupled with genipin cross-linked SF. As the process of MICP is proven to replace cement partially from concrete without negatively influence mechanical properties, SF cross-linked with genipin can provide additional significance in developing low-carbon cement-based composites.

中文翻译：

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京尼平交联自组装丝素蛋白补充建筑材料中微生物碳酸盐沉淀

众所周知，微生物诱导碳酸盐沉淀（MICP）过程可以有效改善建筑材料的工程性能，丝素蛋白（SF）也是如此。因此，在本研究中，我们尝试观察沙子（即基本建筑材料与 MICP 和 SF 的结合）的改进。利用产生脲酶的巨大芽孢杆菌在 Nutri-Calci 培养基中进行 MICP。为了提高SF本身在菌液中的强度，将其与优化浓度3.12 mg/mL的京尼平进行交联。傅里叶变换红外 (FTIR) 光谱证实了 SF 与细菌溶液中京尼平的交联。为了了解这种交联如何改善工程性能，制备了 50 mm ³维的砂模，其抗压强度比用 SF 细菌溶液和仅用 SF 细菌溶液制备的砂模分别高出 35% 和 55%。前一种方解石含量较高。FTIR、SEM、X 射线粉末衍射光谱和 X 射线光电子能谱分析证实，与京尼平交联 SF 结合的细菌溶液中存在较高的生物矿物质沉淀。由于 MICP 工艺已被证明可以部分替代混凝土中的水泥，且不会对机械性能产生负面影响，因此与京尼平交联的 SF 在开发低碳水泥基复合材料方面具有额外的意义。