• Journal of Microbiology and Biotechnology
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• v.31 no.9
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• pp.1311-1322
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• 2021

Microbially induced calcium carbonate precipitation (MICP) has recently become an intelligent and environmentally friendly method for repairing cracks in concrete. To improve on this ability of microbial materials concrete repair, we applied random mutagenesis and optimization of mineralization conditions to improve the quantity and crystal form of microbially precipitated calcium carbonate. Sporosarcina pasteurii ATCC 11859 was used as the starting strain to obtain the mutant with high urease activity by atmospheric and room temperature plasma (ARTP) mutagenesis. Next, we investigated the optimal biomineralization conditions and precipitation crystal form using Plackett-Burman experimental design and response surface methodology (RSM). Biomineralization with 0.73 mol/l calcium chloride, 45 g/l urea, reaction temperature of 45℃, and reaction time of 22 h, significantly increased the amount of precipitated calcium carbonate, which was deposited in the form of calcite crystals. Finally, the repair of concrete using the optimized biomineralization process was evaluated. A comparison of water absorption and adhesion of concrete specimens before and after repairs showed that concrete cracks and surface defects could be efficiently repaired. This study provides a new method to engineer biocementing material for concrete repair.

• 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.

• KSBB Journal
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• v.28 no.3
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• pp.165-169
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• 2013

In this study, 52 ureolytic bacterial strains were newly isolated from various environments. From these, 2 strains (TB-15 and TB-22) were selected based on their high urease activity. XRD spectra clearly showed presence of various sequestration products such as calcite and strontianite in samples. TB-22 showed 20~30% higher survivability upon Sr concentration (20 mM) than Sporosarcina pasteurii KCTC 3558. TB-15 and TB-22 showed 80~90% higher survivability at pH 6 than S. pasteurii. The results demonstrated that the 2 isolates colud be good candidates for the bioremediation of Sr contaminated sites.

• Geosystem Engineering
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• v.21 no.5
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• pp.291-296
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• 2018

The aim of this work is to study the effect of aggregate type on the physico-mechanical properties and microstructure of bio-mortar (BM). Three different aggregates such as sand, dolomite and basalt were used. BM was prepared by mixing aggregates with bacterial cells (Sporosarcina Pasteurii) and one equimolar (1 M) of $urea/CaCl_2.2H_2O$. The results proved that the chemical composition and physical properties of aggregates play an important role in the microbial precipitation rate as well as size, morphology and crystallinity of the precipitated calcite, which strongly reflects on the properties of the prepared BM. The BM containing dolomite gave the highest compressive strength and lowest water absorption.

• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.501-511
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• 2009

This study was conducted to develop self-healing ability of concrete so that inspection could be available even in the event of minute cracks without complex works at any time for more economic concrete structure maintenance and longevity. A completely different method has been carried out in comparison with many of similar researches on self-healing concrete. This is a basic study on the development of self-healing concrete using microbial biomineralization. Compounds were generated except for cells by precipitation reaction of CaC$O_3$ during the microbial metabolism and we examined the use as a binder that hardens the surface of sand using biomineralization that Sporosarcina pasteurii precipitates CaC$O_3$. In result, the formation of new mineral and hardening of sand surface could be verified partly, and it was available for cracks to be repaired by calcite with organic (microorganism) and inorganic (CaC$O_3$) complex structure through the basic experiment a little bit. Therefore the use of biomineralization by this sort of microbial metabolism for concrete structure helps to develop absolute repair-concrete like this concrete with microorganism. The effect of microbial application will be one of the most important research tasks having influence on not only repair for concrete structure but also development of new materials able to reduce environmental problems.

• Journal of the Korean Geotechnical Society
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• v.32 no.5
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• pp.5-13
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• 2016

A calcium source is necessary for calcite precipitation within soil particles by microbial decomposition of urea and a calcium chloride is usually used. The harmful environmental impact of calcium chloride on road, ground and plants is severe. In this study, an eggshell with vinegar is investigated for an environmental-friendly calcium source. Urea-decomposing microorganism and eggshell or calcium chloride as a calcium source are mixed with Ottawa sand to precipitate calcite. Then, the cemented sand with calcite is tested for calcite precipitation, permeability and unconfined compressive strength. A specimen is prepared by loose Ottawa sand in a size of 5 cm in diameter and 10 cm in height. A urea solution with Sporosarcina pasteurii and two different calcium sources is injected into the specimen once a day for 30 days. Calcite precipitated at average of 7.2% on the specimen with eggshell as a calcium source, which was 1.2 times more than that with calcium chloride. The permeability of a specimen with eggshell was at average of 3.82E-5 cm/s, which was 7.7 times lower than that with calcium chloride. Unconfined compressive strength of a specimen with eggshell was at average of 387 kPa, which was 1.2 times higher than that with calcium chloride. As more calcite precipitated, the strength increased while the permeability decreased, regardless of calcium sources.

• 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.

• Journal of Microbiology and Biotechnology
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• v.22 no.3
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• pp.385-389
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• 2012

The application of microorganisms in the field of construction material is rapidly increasing worldwide; however, almost all studies that were investigated were bacterial sources with mineral-producing activity and not with organic substances. The difference in the efficiency of using bacteria as an organic agent is that it could improve the durability of cement material. This study aimed to assess the use of biofilm-forming microorganisms as binding agents to increase the compressive strength of cement-sand material. We isolated 13 alkaliphilic biofilmforming bacteria (ABB) from a cement tetrapod block in the West Sea, Korea. Using 16S RNA sequence analysis, the ABB were partially identified as Bacillus algicola KNUC501 and Exiguobacterium marinum KNUC513. KNUC513 was selected for further study following analysis of pH and biofilm formation. Cement-sand mortar cubes containing KNUC513 exhibited greater compressive strength than mineral-forming bacteria (Sporosarcina pasteurii and Arthrobacter crystallopoietes KNUC403). To determine the biofilm effect, Dnase I was used to suppress the biofilm formation of KNUC513. Field emission scanning electron microscopy image revealed the direct involvement of organic-inorganic substance in cement-sand mortar.

• Journal of Microbiology and Biotechnology
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• v.17 no.1
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• pp.96-103
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• 2007

Plant growth-promoting rhizobacteria (PGPR) have the potential to be used as microbial inoculants to reduce disease incidence and severity and to increase crop yield. Some of the PGPR have been reported to be able to enter plant tissues and establish endophytic populations. Here, we demonstrated an approach to screen bacterial endophytes that have the capacity to promote the growth of pepper seedlings and protect pepper plants against a bacterial pathogen. Initially, out of 150 bacterial isolates collected from healthy stems of peppers cultivated in the Chungcheong and Gyeongsang provinces of Korea, 23 putative endophytic isolates that were considered to be predominating and representative of each pepper sample were selected. By phenotypic characterization and partial 16S rDNA sequence analysis, the isolates were identified as species of Ochrobacterium, Pantoea, Pseudomonas, Sphingomonas, Janthinobacterium, Ralstonia, Arthrobacter, Clavibacter, Sporosarcina, Acidovorax, and Brevundimonas. Among them, two isolates, PS4 and PS27, were selected because they showed consistent colonizing capacity in pepper stems at the levels of $10^6-10^7CFU/g$ tissue, and were found to be most closely related to Pseudomonas rhodesiae and Pantoea ananatis, respectively, by additional analyses of their entire 16S rDNA sequences. Drenching application of the two strains on the pepper seedlings promoted significant growth of peppers, enhancing their root fresh weight by 73.9% and 41.5%, respectively. The two strains also elicited induced systemic resistance of plants against Xanthomonas axonopodis pv. vesicatoria.