Abstract
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.
Highlights
Calcium carbonate (CaCO3) precipitation is a common and circumstantial behavior for sequestration of large amounts of carbon on earth, which accounts for 41.9% of the total carbon[1]
Concrete durability was clearly improved by these pure cultures; there were very few reports concerned with microbial consortia, i.e., multiple interacting microbial populations, which can be more robust in their resistance to environmental fluctuations, perform more complicated tasks and endure more changeable environments than individual populations can[16]
Since microbial consortia can perform more complex tasks and survive in more changeable environments than can uniform populations, the implementation of microbial consortia on crack healing in concrete will be of increasing interest
Summary
Calcium carbonate (CaCO3) precipitation is a common and circumstantial behavior for sequestration of large amounts of carbon on earth, which accounts for 41.9% of the total carbon[1]. Boquet et al showed that almost all kinds of bacteria can mediate the precipitation of CaCO3 if given suitable conditions[3] This was mainly ascribed to their ability to create an alkaline environment through various metabolic activities, such as sulfate reduction, iron reduction, urea hydrolysis, denitrification, methane oxidation and photosynthesis[2]. MICP through ureolysis has certain drawbacks, such as the secondary pollution introduced by the ammonia generated and the limited ureolysis efficiency caused by anaerobic/anoxic conditions To prevent these issues, promising results have been obtained with non-ureolytic bacteria, i.e., B. cohnii, B. pseudofirmus, B. subtilis and B. alkalinitrilicus[14,15]. These bacteria can metabolize organic compounds (e.g., acetate and lactate), instead of urea, as the electron donor to induce the precipitation of CaCO3. Concrete durability was clearly improved by these pure cultures; there were very few reports concerned with microbial consortia, i.e., multiple interacting microbial populations, which can be more robust in their resistance to environmental fluctuations, perform more complicated tasks and endure more changeable environments than individual populations can[16]
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