*3.7.1.3 Precipitation characterization study CaCO3 by Staphylococcus aureus in the presence of microspheres*

The effect of microspheres on the precipitation of the CaCO3, from the microorganism, a kinetic medium, was studied in *St. aureus* solutions in the presence of CaCl2.2H2O, urea, and microspheres. Taking samples at regular intervals, and by characterization of infrared spectroscopy (FT-IR), the existence of the mineral is studied. The microspheres used for this study are water traps.

**Table 10** describes the composition of the solutions of the microorganism in a nutrient solution LB for the kinetic precipitation study of CaCO3.

The development of the microorganism in LB nutrient material with the above quantities of materials. In this particular case, however*, St. Aureus*, which develops, is placed in the stirring incubator for about 24 days in certain conditions (37°C, 100 rpm). At regular


### **Table 10.**

*Quantities of materials used for the kinetic precipitation study of CaCO3 from microorganism solution to LB nutrient material in the presence of micro-water traps.*

### **Figure 18.**

*(A) FT-IR spectrum of CaCO3 kinetic precipitation study by St. aureus in LB nutrient material in the presence of water traps. (B) X-ray radiance spectrum for St. aureus sample in the presence of water microtraps after precipitation of CaCO3.*

intervals, a sample is isolated, centrifuged, sterilized, and eventually characterized via FT-IR, for development certification of CaCO3. In other words, in order to identify the carbonic ion peaks in the FT-IR spectra of the isolated samples, a comparative study is carried out between the sample spectra, the microorganism, and the CaCO3 in LB nutrient. It has emerged that CaCO3, in LB solution, has peaks of 712, 873, and 1409 cm−1 (**Figure 18A**), while the peaks corresponding to the microorganism are as follows: the peak at 1018 cm−1 is attributed to polysaccharides compounds, the peak at 1260 cm−1 in the asymmetric vibration of the bond PO2, at 3274 cm−1 we observe the vibration of N-H, while at 2838 cm−1, we observe the symmetrical vibration of the CH2 bond.

Based on the FT-IR spectrum of **Figure 18**, it appears that CaCO3 is precipitated by *St. aureus* in the LB nutrient material in the presence of water traps. This is demonstrated by the appearance of a peak at 1529 cm−1 where it belongs to the carbonate display area 1530–1320 cm−1. The remaining peaks of the sample spectrum are attributed to components of the microorganism itself and the nutrient LB. Further characterization of CaCO3 precipitation by *St. aureus* in the presence of micro water traps was carried out using the XRD method (**Figure 18B**). According to the X-ray spectrum of the sample, the existence of CaCO3 is certified by the coexistence of all three of its crystalline forms: (a) calcite, C with crystalline levels (006) and (113) and (b) baterite, V (110) and aragonite, A (111).

### **4. Conclusions**

The purpose of this work is the synthesis and characterization of an economical and easily manageable material, which will have an impact on microorganisms by attributing to specific conditions of CaCO3, a mineral that allows the healing of cracks in building materials. More specifically, the composition of microspheres of various types such as PMMA has been studied and their interaction with microorganisms, Gram-positive and Gram-negative, which under appropriate conditions cause CaCO3 precipitation. According to the literature, the most appropriate bacterium in the study of such a case is bacillus (Gram positive, alkalophilic, spore-like bacterium). Due to the inability to find bacillus bacterium, the study was carried out on two types of bacteria, *Escherichia coli* (Gram negative) and *Staphylococcus aureus* (Gram positive). More specifically, however, St. aureus was investigated as it *Self-Healing of Concrete through Ceramic Nanocontainers Loaded with Corrosion Inhibitors… DOI: http://dx.doi.org/10.5772/intechopen.93514*

is a Gram-positive bacterium. The first system studied is water traps. Microspheres of 1 μm size were made, with a uniform size distribution, and from the water absorption study, it was shown that they can respond to aqueous stimuli by increasing their size due to swelling. Such a system could be used to absorb the seeds of the microorganism. The water traps were then coated with SiO2 in order to give the water traps a durable shell, so that in the future when added to the concrete, it protects the adsorbed bacterium from the extreme environment of cement. In the second microsphere synthesis system, the development of an organic (PMMA) and an inorganic (SiO2) transport microsystem is observed. Both types of microspheres were synthesized in aqueous environment, which is chosen by industry for the production of a material, as an economical composition. This contrasts with the composition of the water microtraps and their coatings as the composition was carried out in organic solvent (acetonitrile), which is economically unprofitable for production. The composition of the PMMA and SiO2 microspheres led to production of approximately 1 μm in size, with a uniform size distribution.

The third system concerns the synthesis of microspheres with polyurea shells for the purpose of encasing a substance inside them. Successful synthesis of urea shell capsules was observed when PEG and Triton-x were used as an emulsifier. This shell has useful properties for the industry, as it has great durability and is stable. In the second part of the work, the ability of *Escherichia coli* and *Staphylococcus aureus* to precipitate CaCO3 was studied. The submersion of the mineral is certified by visual characterization as well as by FT-IR spectroscopy. After it has been shown that microspheres are toxic not only to humans (average MTT method) but also to bacteria (visual reculture control after vaccination in a petri dish), it was studied whether they affect the microorganism's submersion of CaCO3. As observed from the data of this study, microorganism remains metabolically active, which leads to precipitation of the mineral, in the presence of microspheres under specific incubation conditions.

Although the bacterium-sphere interaction mechanism has been fully studied, this study shows that the synthesis of micro-bacteria transport systems for the purpose of self-feeding building materials is a promising way to protect the bacterium within cement. Bibliographically, it has been observed that the viability of seeds of the genus Bacillus within cement decreases over time. Thus, the composition of a material where it can protect the bacterium in such an environment, is promising in the field of self-healing. In this way, the performance of the bacterium in precipitation increases, and more effective healing of the crack will be observed. More objective for the composition of such a material is the resulting product to be as manageable and easy to implement as possible, in order to become industrially competitive.
