Understanding the importance of endosporulation methods for generating endospores that can resist harsh conditions and produce calcite in bio self-healing of concrete
Understanding the importance of endosporulation methods for generating endospores that can resist harsh conditions and produce calcite in bio self-healing of concrete
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DOI：
10.1051/matecconf/202337802004
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发表时间：
2023
影响因子：
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通讯作者：
Seyed Ali Rahmaninezhad;M. H. Khaneghahi;Y. Farnam;C. Schauer;Ahmad R. Najafi;Reva M. Street;Amir Sadighi;Divya Kamireddi;Christopher M. Sales
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作者：
Seyed Ali Rahmaninezhad;M. H. Khaneghahi;Y. Farnam;C. Schauer;Ahmad R. Najafi;Reva M. Street;Amir Sadighi;Divya Kamireddi;Christopher M. Sales
用于混凝土生物自愈过程的营养细胞在混凝土硬化过程和使用寿命期间经常面临威胁性的环境条件，例如极端温度、pH、盐度、剪切应力和饥饿。这些情况最终会导致细胞死亡。由于内生孢子可能长时间保持休眠，并且可以在不适宜的条件下存活、萌发和生长，因此它们是引入到混凝土中用于微生物诱导方解石沉淀的合适的细菌表型。本研究调查了不同的内孢子形成方法如何影响内孢子形成率（即，在内孢子形成期间转化为内生孢子的营养细胞的分数），以及萌发率（即，萌发后转化为营养细胞的内生孢子的分数）和萌发的内生孢子在面对混凝土的苛刻条件（特别是冷冻和循环）后的微生物诱导的方解石沉淀（MICP）性能。这项研究的结果表明，热冲击后，细胞在碱性条件下孵育，导致孢子形成和发芽率增加。还观察到，冷冻和解冻循环对内生孢子的方解石产生的影响可以忽略不计，而营养细胞暴露于这些苛刻条件不仅导致生物量和方解石产生减少，而且导致每质量细胞产生的方解石质量减少，如通过热重分析（TGA）所确定的。这项研究的结果为改进内孢子形成和萌发方法提供了关键见解，以有效地将其用于混凝土中的生物自愈应用。
Vegetative cells used for the concrete bio self-healing process often face threatening environmental conditions such as extreme temperature, pH, salinity, shear stress, and starvation during the hardening process and the service life of the concrete. These conditions can eventually lead to cell death. Since endospores are likely to remain dormant for prolonged periods and can survive, germinate, and grow under inhospitable conditions, they are a suitable bacterial phenotype to introduce into concrete for microbial-inducing calcite precipitation. This study investigated how different endosporulation methods affect the endosporulation ratio (i.e., the fraction of vegetative cells that are converted to endospores during endosporulation), as well as the germination ratio (i.e., the fraction of endospores that are converted to vegetative cells following germination) and the microbial-induced calcite precipitation (MICP) performance of germinated endospores after facing harsh conditions of concrete, specifically, freeze and that cycling. Results from this study show that thermal shock followed by cell incubation in alkaline conditions leads to increased sporulation and germination ratios. It was also observed that freeze and thaw cycling had negligible effects on calcite production by endospores, while exposure of vegetative cells to these harsh conditions led to not only less biomass and calcite production but also to a lower mass of calcite produced per mass of cells, as determined by thermogravimetric analysis (TGA). The results from this study provide key insights into improving methods for endosporulation and germination to effectively use them for bio self-healing applications in concrete.