Microbially induced calcium carbonate precipitation and biofilms for microbial applications in biomineralized concrete.

MALDONADO TORALES, MANUELA; MANRRIQUE HUGHES, IVÁN JEREMÍAS; MARZARI, MARÍA JOSEFINA; GUILARDUCCI, ANABELA; CRESPO, KARINA; PARAJE, MARÍA GABRIELA.

Chapadmalal

Congreso; XVIII Congreso de la Sociedad Argentina de Microbiología General.; 2023

samige

Biofilm is defined as a structured community of microbial cells firmly attached to a surfaceand embedded in a 3D extracellular matrix composed of extracellular polymeric substances(EPS). The EPS can protect cells from environmental challenges, promote adhesion todifferent substrates, and provide a microenvironment conducive to biomineralization. Theformation of biotic calcium carbonate (CaCO3) is also known as microbial induced CaCO3precipitation (MICP). To achieve uniform and durable cementation in MICP is necessary tooptimize the fixation capacity and cell viability of bacteria.The present study investigated the ability of Lysinibacillus sphaericus to form biofilms invitro and in situ on cement mortar mixed. The biofilm-forming ability was measured bydetermination of the adhesion on glass, plastic tube, and polystyrene abiotic surfaces andstained with crystal violet. Biofilm formation was investigated at 24, 48, 72 h, and 7 days,the effect of temperature was evaluated at 25 ºC or 37 ºC. The influence of the reductionconditions was assayed in thioglycollate medium (TG), and the formation within Tryptic SoyBroth (TSB) and Luria-Bertani (LB) broth was also studied.When assays were performed on glass and plastic tubes, an increase in biofilm formationwas seen at 37 ºC with respect to 25 ºC. For this condition, the glass tube produced betterbiofilm formation. Quantitative analysis showed that the L. sphaericus cells attached to 96-well plates exhibited good biofilm formation after 72 h and remained up to 7 h. To determinethe optimal temperature for biofilm formation, the L. sphaericus attached to polypropylenewas studied at different temperatures and observed that was more efficient at 37 ºC than at25 ºC. We compared biofilm formation in TSB, LB, and in TG, respectively. The totalproduction of biofilm with TSB medium was found to be approximately the same for LB at37 °C. However, incubation in a TG broth resulted in significantly less biofilm formation.CaCO3 precipitation was produced by L. sphaericus on cement mortar and we found thatthe crystal structure of CaCO3 generated fluorescence radiation in the UV by laser-inducedfluorescence. This technique is used as a diagnostic tool in biology and art with successfulresults thanks to its capability to perform remote, non-destructive, and non-invasivequalitative analyses. Mortar samples without bacterial inoculation were set up as a control.MICP has proved to be better than many conventional technologies because of its ecofriendly nature, self-healing, and energy-efficient technology where microbes are used forremediation of building materials and enhancement in the durability characteristics.Furthermore, biofilms can increase the bridge formation in the void spaces between thesand particles, providing additional nucleation sites for calcium carbonate crystallization,thereby enhancing the effective biocementation and ultimately the mechanical strength ofthe specimen.