Department of Life Science and Environmental Biochemistry/Life and Industry Convergence Research Institute, Pusan National University, Miryang 50463, Republic of Korea.
Department of Biomaterials Science, Pusan National University, Miryang 50463, Republic of Korea.
Sci Total Environ. 2022 Jan 1;802:149841. doi: 10.1016/j.scitotenv.2021.149841. Epub 2021 Aug 22.
Biocalcification is a natural biochemical process, which has been regarded as a promising method for sequestering heavy metals or carbon dioxide in the environment, healing cracks in concrete structures, and stabilizing soil. One of the key factors in this process is calcium carbonate-producing bacteria. The purpose of this study was to maximize the production of calcium carbonate by alkaliphilic Bacillus psychrodurans LC40 isolated from a limestone cave, by manipulating the medium composition for fast and non-detrimental crack healing, and to investigate the mechanism of its production. Strain LC40 could grow well in the strongly alkaline region (pH 9.5-11), indicating its alkaliphilic nature. The optimal medium for calcium carbonate production contained 2% tryptone, 1.5% urea, 0.15% NaHCO, and 150 mM calcium formate (pH 6). Using this medium, the yield of calcium carbonate at 72 h was approximately 8.6-fold higher than that obtained through Urea-CaCl medium. In this culture, the urease and carbonic anhydrase activities were observed simultaneously, and the pH of the medium was found to have increased to 9.4, leading to maximum calcium carbonate production. This suggests that this pH value is achieved by the synergistic action of the two enzymes, resulting in a high calcium carbonate yield. The crystals were characterized by FESEM, EDS and XRD, which confirmed the production of rhombohedral and spherical calcium carbonate crystals containing vaterite and calcite. Strain LC40 completely healed a 0.75 mm wide crack in a very short time of 3 days using the optimized medium as a cementation solution. Our findings indicate that B. psychrodurans LC40 could be a promising candidate for the development of eco-friendly biosealant applicable to environmentally stressed concrete structures.
生物钙化是一种自然的生化过程，已被视为一种有前途的方法，可以用于环境中重金属或二氧化碳的固定、混凝土结构裂缝的愈合以及土壤的稳定。这个过程的关键因素之一是产生碳酸钙的细菌。本研究的目的是通过操纵培养基组成来最大限度地提高从石灰岩洞分离出的嗜碱芽孢杆菌（Bacillus psychrodurans）LC40 的碳酸钙产量，以实现快速且无损的裂缝愈合，并研究其产生机制。菌株 LC40 可以在强碱区域（pH 9.5-11）中良好生长，表明其具有嗜碱性。碳酸钙产量的最佳培养基含有 2%胰蛋白胨、1.5%尿素、0.15%NaHCO 和 150mM 甲酸钠（pH 6）。使用该培养基，碳酸钙的产量在 72 小时时约为使用 Urea-CaCl 培养基时的 8.6 倍。在该培养物中，同时观察到脲酶和碳酸酐酶的活性，并且发现培养基的 pH 值增加到 9.4，导致最大的碳酸钙产量。这表明该 pH 值是由两种酶的协同作用达到的，从而产生了高的碳酸钙产量。FESEM、EDS 和 XRD 对晶体进行了表征，证实了菱形和球形碳酸钙晶体的产生，其中含有文石和方解石。使用优化的培养基作为胶结溶液，菌株 LC40 在非常短的 3 天内完全愈合了 0.75mm 宽的裂缝。我们的研究结果表明，嗜碱芽孢杆菌 LC40 可能是一种有前途的候选物，可用于开发适用于环境胁迫混凝土结构的环保型生物密封剂。
