• KSBB Journal
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• v.32 no.3
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• pp.206-211
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• 2017

The physical method used to prevent a landslide has the risk of environmental pollution. Calcite forming bacteria (CFB) have been received increasing attention as a novel and environmental friendly strategy for the soil improvement. In this study, we selected 11 CFB strains with high calcite production. We also examined survivability and calcite productivity of the strains under various stress conditions to select strains with high resistance to various stresses. Two strains was selected by environment stress. Sphingobacterium sp. KJ-32 and Viridibacillus arenosi B-25 precipitate calcite more than other strains at pH 5 and $15^{\circ}C$ respectively. Bio-consolidated soil cakes were made using various calcium salts (calcium chloride, calcium acetate, calcium lactate, calcium gluconate) with mixed culture of 2 strains. Among them, the calcite made using calcium chloride was the largest. These observations demonstrate that this bio-consolidation technology has the potential for eco-friendly prevention of landslide and soil improvement.

• KSBB Journal
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• v.29 no.5
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• pp.323-327
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• 2014

Microbially induced calcite precipitation is a naturally occurring biological process in which microbes produce calcite on the surface of the microorganisms by urease activity. In order to collect calcite forming bacteria (CFB) in Korea, we isolated 343 putative CFB strains from various environments over three year period (2011~2013) and selected 100 CFB strains. Average of calcite productivity was 10.56 mg/mL. And average of ammonium concentration by urease activity was $8.00{\mu}M$. Two useful CFB strains of the others were analyzed by 16S rRNA and identified as Sporosarcina sp. and Viridibacillus arenosi. The CFB strains presented in this study are indigenous microorganisms in Korea and they are expected to be applicable to a variety of environments in the country.

• Journal of Microbiology and Biotechnology
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• v.27 no.7
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• pp.1331-1335
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• 2017

In this study, the feasibility of introducing calcite-forming bacteria into concrete pavements to improve their mechanical performance was investigated. Lysinibacillus sphaericus WJ-8, which was isolated in a previous study and is capable of exhibiting high urease activity and calcite production, was used. When analyzed via scanning electron microscopy (SEM) and X-ray diffraction, WJ-8 showed a significant amount of calcite precipitation. The compressive strength of cement mortar mixed with WJ-8 cells and nutrient medium (urea with calcium lactate) increased by 10% compared with that of the controls. Energy dispersive x-ray spectroscopy analyses confirmed that the increase in strength was due to the calcite formed by the WJ-8 cells.

• KSBB Journal
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• v.29 no.3
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• pp.188-192
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• 2014

Calcite forming bacteria (CFB) have been received increasing attention as a novel and environmental friendly strategy for the healing of concrete crack. Among the CFB, spore forming bacteria were proposed to overcome concrete condition (high pH, hydration heat, deicer). In this study, Lysinibaclillus sphaericus WJ-8 (WJ-8) isolated from concrete pavement was characterized. The WJ-8 was able to precipitate calcite at 10 mg/mL. When observed by scanning electron microscopy, WJ-8 showed spore formation and maximum spore yield was approximately 97.9%. Also response of spores against various environment stresses was examined. Approximately 83~97% of spores maintained their survivability at each three conditions ($60^{\circ}C$, 3 M NaCl and pH 12).

• Journal of Microbiology and Biotechnology
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• v.23 no.9
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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.

• KSBB Journal
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• v.27 no.4
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• pp.268-272
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• 2012

Microbially induced calcite precipitation (MICP) has been explored for protection and consolidation of construction materials such as concrete. In this study, we isolated 54 calcite forming bacteria from concrete pavement and selected 5 isolates which showed high specific urease activity. Also response of the 5 strains against various environmental stresses was examined. BC 4 and BC 5 showed 35% and 26% viability at heat stress ($50^{\circ}C$), respectively. BC 1 and BC 4 maintained 60.4% and 70.4% viability upon osmotic stress (1 M NaCl), respectively. Among the 5 isolates BC 4 had the highest viability upon alkaline stress (pH 10).

• Journal of Microbiology and Biotechnology
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• v.20 no.4
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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.

• Microbiology and Biotechnology Letters
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• v.39 no.3
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• pp.287-293
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• 2011

The purpose of this study was to isolate and characterize fungal deteriogens, which induce discoloration of the cement tunnel, and calcite forming bacteria (CFBs), which have antifungal activity against fungal deteriogens. Isolation of mold, bacteria and yeast was performed using several solid media and partially identified using internal transcribed spacer (ITS); 5.8S rRNA gene sequencing and 16s rDNA sequencing. A total of 19 microbial strains were identified with the most widely distributed fungal strain being Cladospirum sphaerospermum. In addition, five bacteria derived from the tunnel were identified as CFBs. Amongst the latter, Bacillus aryabhatti KNUC205 exhibited antifungal activity against Cladospirum sphaerospermum KNUC253 and Aspergillus niger KCTC6906 as concentrated filtered supernatants.

• Journal of Microbiology and Biotechnology
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• v.22 no.7
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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 the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.395-402
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• 2017

Recently, many researches on crack healing and repairing technique using bacteria which can produce vital-reacted calcite have been proposed. This study is for a basic research on repair material with slime formation through bacteria and deals with durability evaluation for coating materials containing bacteria-forming slime. For the work, 4 types of bacteria (Rhodobacter capsulatus, Rhodopseudomonas palustris, Bacillus thuringiensis, and Bacillus subtilis) and 2 types of nutrient conditions are considered, and several tests covering strength evaluation under sulfate condition, accelerated chloride diffusion, and UV (Ultrasonic Velocity) measurement are performed. Strength improvement in coating materials containing bacteria is evaluated in spite of even exposure to sulfate attack to 7 days. Chloride diffusion coefficient and UV properties are also improved except for the case of Rhodopseudomonas palustris. With resistance of slime to long term exposure and aerobic conditions for bacteria longevity, the proposed bacteria shows an engineering feasibility for repair material of RC structure exposed harsh environment.