• Journal of Microbiology and Biotechnology
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• 제22권11호
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• pp.1568-1574
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• 2012

Microbiological calcium carbonate precipitation (MCCP) has been investigated for its ability to improve the durability of cement mortar. However, very few strains have been applied to crack remediation and strengthening of cementitious materials. In this study, we report the biodeposition of Bacillus subtilis 168 and its ability to enhance the durability of cement material. B. subtilis 168 was applied to the surface of cement specimens. The results showed a new layer of deposited organic-inorganic composites on the surface of the cement paste. In addition, the water permeability of the cement paste treated with B. subtilis 168 was lower than that of non-treated specimens. Furthermore, artificial cracks in the cement paste were completely remediated by the biodeposition of B. subtilis 168. The compressive strength of cement mortar treated with B. subtilis 168 increased by about 19.5% when compared with samples completed with only B4 medium. Taken together, these findings suggest that the biodeposition of B. subtilis 168 could be used as a sealing and coating agent to improve the strength and water resistance of concrete. This is the first paper to report the application of Bacillus subtilis 168 for its ability to improve the durability of cement mortar through calcium carbonate precipitation.

• 한국미생물·생명공학회지
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• 제40권3호
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• pp.169-179
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• 2012

미생물에 의한 탄산칼슘침전은 생물 화학적으로 풍화, 침식된 시멘트 건축구조물 표면의 미학적 복원 및 수분침투 방지를 목적으로 응용되었다. 이 기술의 두드러진 장점이 보고된 후 유럽과 미국을 중심으로 미생물을 이용한 건축공학적 응용가능성에 대한 연구가 활발히 이루어져 왔다. 견고하고 원재료와의 호환성이 뛰어난 이 기술은 다양한 탄산칼슘형성세균의 선별 또는 배양 및 적용방법의 개발로 그 관심이 촉발되었다. 본 총설의 목적은 친환경적 건축소재에 대한 관심이 높아지고 그 필요성이 대두되고 있는 현 시점에서 미생물 탄산칼슘형성 매카니즘과 그 관련 기술들을 검토해 보고자 한다. 본론에선 시멘트 건축물 표면코팅 효과에 대한 방법론적 연구사례들을 조사하였고, 시멘트 구조물의 내구성 증진을 위한 미생물의 첨가에 대한 연구사례들도 함께 살펴보았다. 부가적으로 향후 미생물의 다기능성을 이용한 자기수복 스마트 콘크리트 개발에 대한 개념을 살펴보고 그 미래를 전망하였다.

• Journal of Microbiology and Biotechnology
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• 제20권4호
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• pp.782-788
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• 2010

Microbiological calcium carbonate precipitation (MCP) has been investigated for its ability to improve the compressive strength of mortar. However, very few studies have been conducted on the use of calcite-forming bacteria (CFB) to improve compressive strength. In this study, we discovered new bacterial genera that are capable of improving the compressive strength of mortar. We isolated 4 CFB from 7 environmental concrete structures. Using sequence analysis of the 16S rRNA genes, the CFB could be partially identified as Sporosarcina soli KNUC401, Bacillus massiliensis KNUC402, Arthrobacter crystallopoietes KNUC403, and Lysinibacillus fusiformis KNUC404. Crystal aggregates were apparent in the bacterial colonies grown on an agar medium. Stereomicroscopy, scanning electron microscopy, and X-ray diffraction analyses illustrated both the crystal growth and the crystalline structure of the $CaCO_3$ crystals. We used the isolates to improve the compressive strength of cement-sand mortar cubes and found that KNUC403 offered the best improvement in compressive strength.

• Journal of Microbiology and Biotechnology
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• 제22권7호
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• pp.1015-1020
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• 2012

Antifungal cement mortar or microbiological calcium carbonate precipitation on cement surface has been investigated as functional concrete research. However, these research concepts have never been fused with each other. In this study, we introduced the antifungal calcite-forming bacteria (CFB) Bacillus aryabhattai KNUC205, isolated from an urban tunnel (Daegu, South Korea). The major fungal deteriogens in urban tunnel, Cladosporium sphaerospermum KNUC253, was used as a sensitive fungal strain. B. aryabhattai KNUC205 showed $CaCO_3$ precipitation on B4 medium. Cracked cement mortar pastes were made and neutralized by modified methods. Subsequently, the mixture of B. aryabhattai KNUC205, conidiospore of C. sphaerospermum KNUC253, and B4 agar was applied to cement cracks and incubated at $18^{\circ}C$ for 16 days. B. aryabhattai KNUC205 showed fungal growth inhibition against C. sphaerospermum. Furthermore, B. aryabhattai KNUC205 showed crack remediation ability and water permeability reduction of cement mortar pastes. Taken together, these results suggest that the $CaCO_3$ precipitation and antifungal properties of B. aryabhattai KNUC205 could be used as an effective sealing or coating material that can also prevent deteriorative fungal growth. This study is the first application and evaluation research that incorporates calcite formation with antifungal capabilities of microorganisms for an environment-friendly and more effective protection of cement materials. In this research, the conception of microbial construction materials was expanded.

• Journal of Microbiology and Biotechnology
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• 제23권9호
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• pp.1269-1278
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• 2013

Crack remediation on the surface of cement mortar using microbiological calcium carbonate ($CaCO_3$) precipitation (MICP) has been investigated as a microbial sealing agent on construction materials. However, MICP research has never acknowledged the antifungal properties of calcite-forming bacteria (CFB). Since fungal colonization on concrete surfaces can trigger biodeterioration processes, fungi on concrete buildings have to be prevented. Therefore, to develop a microbial sealing agent that has antifungal properties to remediate cement cracks without deteriorative fungal colonization, we introduced an antifungal CFB isolated from oceanic islands (Dokdo islands, territory of South Korea, located at the edge of the East Sea in Korea.). The isolation of CFB was done using B4 or urea-$CaCl_2$ media. Furthermore, antifungal assays were done using the pairing culture and disk diffusion methods. Five isolated CFB showed $CaCO_3$ precipitation and antifungal activities against deteriorative fungal strains. Subsequently, five candidate bacteria were identified using 16S rDNA sequence analysis. Crack remediation, fungi growth inhibition, and water permeability reduction of antifungal CFB-treated cement surfaces were tested. All antifungal CFB showed crack remediation abilities, but only three strains (KNUC2100, 2103, and 2106) reduced the water permeability. Furthermore, these three strains showed fungi growth inhibition. This paper is the first application research of CFB that have antifungal activity, for an eco-friendly improvement of construction materials.