AlkaliphilicBacillusspecies show potential application in concrete crack repair by virtue of rapid spore production and germination then extracellular calcite formation
Abstract:Aims: Characterization of alkaliphilic Bacillus species for spore production and germination and calcite formation as a prelude to investigate their potential in microcrack remediation in concrete. Methods and Results: Conditions, extent and timing of endospore production was determined by dark-field light microscopy; germination induction and kinetics were assessed by combining reduction in optical density with formation of refractile bodies by phase-contrast microscopy. Bacillus pseudofirmus was selected fro… Show more
“…After 28 days of healing, the selected cracks of the three bacteria-based concrete specimens were almost completely healed (the crack widths were 0.32~0.56 mm), while those of the control specimen were barely healed (the crack width was 0.27 and 0.46 mm). A beige deposit could be visibly observed at the surface of the bacteria-based specimens, which was consistent with studies using pure cultures 15 , 23 , 39 . Figure 6 Microscopic images of four types of crack-healing processes.…”
Current studies have employed various pure-cultures for improving concrete durability based on microbially induced carbonate precipitation (MICP). However, there have been very few reports concerned with microbial consortia, which could perform more complex tasks and be more robust in their resistance to environmental fluctuations. In this study, we constructed three microbial consortia that are capable of MICP under aerobic (AE), anaerobic (AN) and facultative anaerobic (FA) conditions. The results showed that AE consortia showed more positive effects on inorganic carbon conversion than AN and FA consortia. Pyrosequencing analysis showed that clear distinctions appeared in the community structure between different microbial consortia systems. Further investigation on microbial community networks revealed that the species in the three microbial consortia built thorough energetic and metabolic interaction networks regarding MICP, nitrate-reduction, bacterial endospores and fermentation communities. Crack-healing experiments showed that the selected cracks of the three consortia-based concrete specimens were almost completely healed in 28 days, which was consistent with the studies using pure cultures. Although the economic advantage might not be clear yet, this study highlights the potential implementation of microbial consortia on crack healing in concrete.
“…After 28 days of healing, the selected cracks of the three bacteria-based concrete specimens were almost completely healed (the crack widths were 0.32~0.56 mm), while those of the control specimen were barely healed (the crack width was 0.27 and 0.46 mm). A beige deposit could be visibly observed at the surface of the bacteria-based specimens, which was consistent with studies using pure cultures 15 , 23 , 39 . Figure 6 Microscopic images of four types of crack-healing processes.…”
Current studies have employed various pure-cultures for improving concrete durability based on microbially induced carbonate precipitation (MICP). However, there have been very few reports concerned with microbial consortia, which could perform more complex tasks and be more robust in their resistance to environmental fluctuations. In this study, we constructed three microbial consortia that are capable of MICP under aerobic (AE), anaerobic (AN) and facultative anaerobic (FA) conditions. The results showed that AE consortia showed more positive effects on inorganic carbon conversion than AN and FA consortia. Pyrosequencing analysis showed that clear distinctions appeared in the community structure between different microbial consortia systems. Further investigation on microbial community networks revealed that the species in the three microbial consortia built thorough energetic and metabolic interaction networks regarding MICP, nitrate-reduction, bacterial endospores and fermentation communities. Crack-healing experiments showed that the selected cracks of the three consortia-based concrete specimens were almost completely healed in 28 days, which was consistent with the studies using pure cultures. Although the economic advantage might not be clear yet, this study highlights the potential implementation of microbial consortia on crack healing in concrete.
“…This has limited our understanding of alternative pathways, and the factors affecting efficient calcite precipitation in nonureolytic bacteria are not clear. Studies on self-healing concrete using alkaliphilic nonureolytic bacteria such as Bacillus pseudofirmus and Bacillus cohnii have shown great promise and have led to similar levels of self-healing at the laboratory scale as ureolytic bacteria (19,20). To fully assess the potential of MICP for industrial and environmental use, detailed understanding of the microorganism, mechanism of precipitation, and application is therefore important.…”
Microbially induced calcite precipitation (MICP) has not only helped to shape our planet’s geological features but is also a promising technology to address environmental concerns in civil engineering applications. However, limited understanding of the biomineralization capacity of environmental bacteria impedes application. We therefore surveyed the environment for different mechanisms of precipitation across bacteria. The most fundamental difference was in ureolytic ability, where urease-positive bacteria caused rapid, widespread increases in pH, whereas nonureolytic strains produced such changes slowly and locally. These pH shifts correlated well with patterns of precipitation on solid medium. Strikingly, while both mechanisms led to high levels of precipitation, we observed clear differences in the precipitate. Ureolytic bacteria produced homogenous, inorganic fine crystals, whereas the crystals of nonureolytic strains were larger and had a mixed organic/inorganic composition. When representative strains were tested in application for crack healing in cement mortars, nonureolytic bacteria gave robust results, while ureolytic strains showed more variation. This may be explained by our observation that urease activity differed between growth conditions or by the different natures and therefore different material performances of the precipitates. Our results shed light on the breadth of biomineralization activity among environmental bacteria, an important step toward the rational design of bacterially based engineering solutions.
IMPORTANCE Biomineralization triggered by bacteria is important in the natural environment and has many applications in industry and in civil and geotechnical engineering. The diversity in biomineralization capabilities of environmental bacteria is, however, not well understood. This study surveyed environmental bacteria for their ability to precipitate calcium carbonate minerals and investigated both the mechanisms and the resulting crystals. We show that while urease activity leads to the fastest precipitation, it is by no means essential. Importantly, the same quantities of calcium carbonate are produced by nonureolytic bacteria, and the resulting crystals appear to have larger volumes and more organic components, which are likely beneficial in specific applications. Testing both precipitation mechanisms in a self-healing concrete application showed that nonureolytic bacteria delivered more robust results. Here, we performed a systematic study of the fundamental differences in biomineralization between environmental bacteria, and we provide important information for the design of bacterially based engineering solutions.
“…Com intuito de estabelecer uma alternativa sustentável e rentável, a MICP tem sido estudada para aplicação em cicatrização de fissuras em concreto (SHARMA et al, 2017). Zhong e Islam (1995) utilizaram a consolidação de misturas de areia, compostas por bactérias, nutrientes e um material de preenchimento para remediação de rachaduras em granito.…”
RESUMOA biomineralização é uma alteração química em um ambiente através de atividade microbiana que resulta na precipitação de minerais, sendo um fenômeno amplamente distribuído na natureza. Na precipitação de carbonato de cálcio induzida microbiologicamente (MICP, do inglês microbially induced calcium carbonate precipitation), a urease apresenta papel importante ao hidrolisar a ureia, por uma grande variedade de micro-organismos capazes de produzir elevados níveis desta enzima. Existem diferentes polimorfos do cristal de carbonato de cálcio e a estrutura que é formada depende do tipo da fonte de cálcio utilizada, período de incubação e atividades metabólicas referentes à espécie microbiana avaliada. A MICP é uma alternativa promissora e ambientalmente amigável para as tecnologias de remediação atuais e convencionais capazes de resolverem problemas ambientais em campos multidisciplinares. Várias aplicações como aumento da qualidade e da melhoria das propriedades de materiais de construção, remoção de metais potencialmente tóxicos e radionucleotídeos e sequestro de dióxido de carbono atmosférico têm sido discutidas. PALAVRAS-CHAVE: Biomoneralização, carbonato de cálcio, construção civil, MICP, urease.
CALCIUM CARBONATE BIOPRECIPITATION BY UREOLYTIC BACTERIA AND ITS APPLICATIONSABSTRACT Biomineralization is a chemical change in environment through the microbial activity that results in the precipitation of minerals, being a phenomenon widely spread in nature. In microbially induced carbonate precipitation (MICP), ureases plays an important role in hydrolyzing urea by a large variety of microorganisms capable of producing high levels of this enzyme. There are different polymorphs of calcium carbonate crystal and the structure that is formed depends on the type of calcium used, the incubation time and metabolic activities of the evaluated microbrial species.
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