Isolation of alkaliphilic calcifying bacteria and their feasibility for enhanced CaCO₃ precipitation in bio‐based cementitious composites

Abstract

Microbially induced calcite precipitation (MICP), secreted through biological metabolic activity, secured an imperative position in remedial measures within the construction industry subsequent to ecological, environmental and economical returns. However, this contemporary recurrent healing system is susceptible to microbial depletion in the highly alkaline cementitious environment. Therefore, researchers are probing for alkali resistant calcifying microbes. In the present study, alkaliphilic microbes were isolated from different soil sources and screened for probable CaCO 3 precipitation. Non-ureolytic pathway (oxidation of organic carbon) was adopted for calcite precipitation to eliminate the production of toxic ammonia. For this purpose, calcium lactate Ca(C 3 H 5 O 3 ) 2 and calcium acetate Ca (CH 3 COO) 2 were used as CaCO 3 precipitation precursors. The quantification protocol for precipitated CaCO 3 was established to select potent microbial species for implementation in the alkaline cementitious systems as more than 50% of isolates were able to precipitate CaCO 3 . Results suggested 80% of potent calcifying strains isolated in this study, portrayed higher calcite precipitation at pH 10 when compared to pH 7. Ten superlative morphologically distinct isolates capable of CaCO 3 production were identified by 16SrRNA sequencing. Sequenced microbes were identified as species of Bacillus, Arthrobacter, Planococcus, Chryseomicrobium and Corynebacterium. Further, microstructure of precipitated CaCO 3 was inspected through scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermal gravimetric (TG) analysis. Then, the selected microbes were investigated in the cementitious mortar to rule out any detrimental effects on mechanical properties. These strains showed maximum of 36% increase in compressive strength and 96% increase in flexural strength.Bacillus, Arthrobacter, Corynebacterium and Planococcus genera have been reported as CaCO 3 producers but isolated strains have not yet been investigated in conjunction with cementitious mortar. Moreover, species of Chryseomicrobium and Glutamicibacter were reported first time as calcifying strains.

Development of Immediate Release Tablets Containing Calcium Lactate Synthetized from Black Sea Mussel Shells

“…The thermal curves (TGA-DTA-DTG) of the synthesized calcium lactate are shown in Figure 5. As reported in the literature, four mass loss steps are included in the thermal decomposition of calcium lactate pentahydrate [24,25]…”

Bacterial Carbonate Precipitation Using Active Metabolic Pathway to Repair Mortar Cracks

“…Autogenous healing is achieved due to anhydrous cement particles which cause secondary hydration via water infiltration through micro-cracks, whereas autonomous healing is achieved by using super absorbent polymer (SAP), admixtures, and microbes [ 5 , 6 ]. Microbially induced calcite precipitation (MICP) takes place using calcifying bacteria through metabolic activity [ 5 ]. Autonomous concrete crack-repairing techniques are further divided into two major categories.…”

“…Autonomous concrete crack-repairing techniques are further divided into two major categories. One method involves mixing bio-suspension into fresh concrete before cracks form, resulting in self-healing concrete [ 2 , 5 , 7 ]. Other concrete repair approaches include manually applying bio-suspension to existing cracks on concrete surfaces that lack a self-healing process [ 1 ].…”

“…The use of calcifying microorganisms in microbial precipitation has substantially enhanced the durability and mechanical strength of concrete [ 5 ]. The microbial pathway’s ability to repair the cementitious system is based on metabolic activity producing calcium carbonate, which is governed by nucleation sites, high concrete alkalinity, calcium ions, and dissolved inorganic chemicals.…”

“…The microbial pathway’s ability to repair the cementitious system is based on metabolic activity producing calcium carbonate, which is governed by nucleation sites, high concrete alkalinity, calcium ions, and dissolved inorganic chemicals. Furthermore, bacteria’s ability to precipitate bio-calcite is influenced by bacterial strain, pH, temperature, the precipitation process, and nutrient supply [ 5 ]. Calcium carbonate (CaCO 3 ) precipitation is produced by bacteria that are either autotrophic or heterotrophic [ 8 ].…”