ISOLATION OF BACTERIA ASSOCIATED TO CONCRETE: FUTURE STUDIES ON THE PRODUCTION OF BIOCONCRETE

The biomineralization has been gaining attention of researchers because it consists of a natural processof the metabolism from some microorganisms, resulting in the precipitation of minerals, such as calcium carbonate (CaCO3), which can promote the solidification of materials. Among its sustainable applications, production of bioconcrete by these microorganisms stands out, which can support civil construction through the improvement of cement materials quality, treating concrete cracks, strengthening soil and slopes, as well as fortificating foundations, bridges and dams against natural catastrophes. In this context, the present study aimed to isolate and identify microorganisms capable of living associated to concrete and that may be compatible to bioconcrete production. Concrete samples consisting of blocks of approximately 15 centimeters werepacked in sterile vials and scrapped with the aidof spatulas. The scraped concrete was added to Erlenmeyers with the nutritive liquid medium (NB) and this suspension was kept for 7 days under 37 ºC and 150 rpm for bacterial growth. Serial dilutions were performed (10-1, 10-2 and 10-3) and 50 μL of each dilution were inoculated in solid NA culture medium. After 5 days of incubation, bacterial colonies were purified and preserved in 20% glycerol at -20 ºC. Morphological analyzes (macro and microscopic –Gram staining) as well as biochemical tests (catalase activity –3% hydrogen peroxide) were performed. Six strains were isolated (named BC1 to BC6), and colonies colors varied from yellow to orange. Five bacteria showed Gram-negative characteristics (red) while one bacteria (BC6) showed Gram-positive characteristic (purple). The morphology of bacilluswas identified within all bacteria colonies, being the isolates BC1 and BC4 characterized as coccobacillus andisolate BC5 characterized as streptobacillus. All six isolates were shown to be catalase positive in biochemical tests. The genus Bacillus has been frequently related to concrete biomineralization processes, among them Bacillus thuringiensis, B. subtilis e B. pasteurii species. Results demonstrate that the isolates can live associated to concrete, and strengthens future studies on the detailing of their role in this microenvironment as well as encourage future commercial applications.