Characterization of a Novel CaCO3-Forming Alkali-Tolerant Rhodococcus erythreus S26 as a Filling Agent for Repairing Concrete Cracks.

Seunghoon Choi,O-Mi Lee,Sungjin Park,Minjoo Park,Kwang Min Lee,Hong-Joo Son,Yerin Kim

doi:10.3390/molecules26102967

Seunghoon Choi, O-Mi Lee + Show 5 more

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https://doi.org/10.3390/molecules26102967

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Abstract

Biomineralization, a well-known natural phenomenon associated with various microbial species, is being studied to protect and strengthen building materials such as concrete. We characterized Rhodococcus erythreus S26, a novel urease-producing bacterium exhibiting CaCO3-forming activity, and investigated its ability in repairing concrete cracks for the development of environment-friendly sealants. Strain S26 grown in solid medium formed spherical and polygonal CaCO3 crystals. The S26 cells grown in a urea-containing liquid medium caused culture fluid alkalinization and increased CaCO3 levels, indicating that ureolysis was responsible for CaCO3 formation. Urease activity and CaCO3 formation increased with incubation time, reaching a maximum of 2054 U/min/mL and 3.83 g/L, respectively, at day four. The maximum CaCO3 formation was achieved when calcium lactate was used as the calcium source, followed by calcium gluconate. Although cell growth was observed after the induction period at pH 10.5, strain S26 could grow at a wide range of pH 4–10.5, showing its high alkali tolerance. FESEM showed rhombohedral crystals of 20–60 µm in size. EDX analysis indicated the presence of calcium, carbon, and oxygen in the crystals. XRD confirmed these crystals as CaCO3 containing calcite and vaterite. Furthermore, R. erythreus S26 successfully repaired the artificially induced large cracks of 0.4–0.6 mm width.

Highlights

Calcium carbonate (CaCO3 ) formation is a representative example of bacterial mineralization occurring because of the involvement of various bacterial genera in a wide range of natural environments; this process is known as bacterially induced CaCO3 precipitation (BICP) [1]
From the viewpoint of eco-friendliness and cost reduction, new cementitious materials for repairing structural cracks such as BICP, which is known as the Molecules 2021, 26, 2967 and the environment [5]
We described an environment-friendly and efficient microbiological method for sealing cracks using R. erythreus S26 as a concrete healing agent

Summary

Introduction

Calcium carbonate (CaCO3 ) formation is a representative example of bacterial mineralization occurring because of the involvement of various bacterial genera in a wide range of natural environments; this process is known as bacterially induced CaCO3 precipitation (BICP) [1]. The most promising among them is the use of BICP to repair damaged concrete structures and historically important stone cultural heritages [4]. Various processes, such as physicochemical weathering, biological corrosion, ground subsidence, and human activity, cause cracks in concrete and stone structures. From the viewpoint of eco-friendliness and cost reduction, new cementitious materials for repairing structural cracks such as BICP, which is known as the Molecules 2021, 26, 2967 and the environment [5]. From the viewpoint of eco-friendliness and cost reduction, new cementitious materials for repairing structural cracks such as BICP, which is known as the self-healing technique, have gained attention.

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