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Nanoscale Characterization of Fungal-Induced CaCO3 Precipitation : Implications for Self-Healing Concrete

Tuyishime, J R Marius LU ; Hammer, Edith C LU orcid ; Pla-Ferriol, Martí LU ; Thånell, Karina LU ; Alwmark, Carl LU ; van Velzen, Sophie LU ; Floudas, Dimitrios LU ; Platakyte, Rasa LU orcid ; Obst, Martin and Zou, Hanbang LU (2025) In ACS applied materials & interfaces 17(26). p.37648-37656
Abstract

Cracks in concrete compromise structural integrity by exposing steel reinforcement to corrosion agents, shortening its service life. Fungal-induced calcium carbonate (CaCO3) precipitation via urea hydrolysis offers a fast and robust self-healing mechanism to seal the cracks, extending the lifespan while reducing the carbon (C) footprint of concrete infrastructure. However, current studies rely on bulk-scale analytical methods, which lack the spatial resolution and chemical sensitivity to distinguish and map CaCO3 polymorphs at the nanoscale. This study combined scanning electron microscopy (SEM) and synchrotron-based scanning transmission X-ray microscopy (STXM) with near-edge X-ray absorption fine structure... (More)

Cracks in concrete compromise structural integrity by exposing steel reinforcement to corrosion agents, shortening its service life. Fungal-induced calcium carbonate (CaCO3) precipitation via urea hydrolysis offers a fast and robust self-healing mechanism to seal the cracks, extending the lifespan while reducing the carbon (C) footprint of concrete infrastructure. However, current studies rely on bulk-scale analytical methods, which lack the spatial resolution and chemical sensitivity to distinguish and map CaCO3 polymorphs at the nanoscale. This study combined scanning electron microscopy (SEM) and synchrotron-based scanning transmission X-ray microscopy (STXM) with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to characterize fungal CaCO3 polymorphs at the nanoscale. CaCO3 biominerals precipitated by three urease-positive fungi were sectioned into 75-200 nm thin layers. STXM data were collected from at least two spots per section, focusing on Ca (L-edge) and C (K-edge) chemical speciation and elemental quantitative mapping. Calcite, the thermodynamically most stable polymorph, was identified as the predominant mineral phase precipitated by all fungi species, while aragonite and non-CO3-Ca species (CaCl2 or Ca adsorbed onto extracellular polymeric substances (EPS)) occurred as minor components. In fungal species 2, we observed nanoscale heterogeneity in Ca phases across five analyzed spots, three dominated by calcite with minor contributions of other Ca species, while the others showed mixed CaCO3/non-CO3 phases, as confirmed by NEXAFS spectra. These findings suggest that biomineralization in the fungal micro and nanoenvironment is influenced by localized physicochemical and metabolic conditions that shape mineral phases. C NEXAFS spectra further supported the Ca data, showing C-specific spectral features in the calcite-rich regions across all samples. This underscores STXM's capability to resolve complexities and mechanisms of fungal CaCO3 formation (e.g., mineral phase composition, fungal organic-mineral interactions, and spatial heterogeneity). Overall, this study provides critical nanoscale insights into fungal CaCO3 precipitation, thus providing valuable guidance in optimizing fungal systems in self-healing concrete applications.

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author
; ; ; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
ACS applied materials & interfaces
volume
17
issue
26
pages
9 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • pmid:40542343
  • scopus:105008926483
ISSN
1944-8244
DOI
10.1021/acsami.5c07137
language
English
LU publication?
yes
id
8c345474-a914-46b6-8cb4-49b00cb1e120
date added to LUP
2025-07-10 09:34:02
date last changed
2025-08-12 11:13:37
@article{8c345474-a914-46b6-8cb4-49b00cb1e120,
  abstract     = {{<p>Cracks in concrete compromise structural integrity by exposing steel reinforcement to corrosion agents, shortening its service life. Fungal-induced calcium carbonate (CaCO<sub>3</sub>) precipitation via urea hydrolysis offers a fast and robust self-healing mechanism to seal the cracks, extending the lifespan while reducing the carbon (C) footprint of concrete infrastructure. However, current studies rely on bulk-scale analytical methods, which lack the spatial resolution and chemical sensitivity to distinguish and map CaCO<sub>3</sub> polymorphs at the nanoscale. This study combined scanning electron microscopy (SEM) and synchrotron-based scanning transmission X-ray microscopy (STXM) with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to characterize fungal CaCO<sub>3</sub> polymorphs at the nanoscale. CaCO<sub>3</sub> biominerals precipitated by three urease-positive fungi were sectioned into 75-200 nm thin layers. STXM data were collected from at least two spots per section, focusing on Ca (L-edge) and C (K-edge) chemical speciation and elemental quantitative mapping. Calcite, the thermodynamically most stable polymorph, was identified as the predominant mineral phase precipitated by all fungi species, while aragonite and non-CO<sub>3</sub>-Ca species (CaCl<sub>2</sub> or Ca adsorbed onto extracellular polymeric substances (EPS)) occurred as minor components. In fungal species 2, we observed nanoscale heterogeneity in Ca phases across five analyzed spots, three dominated by calcite with minor contributions of other Ca species, while the others showed mixed CaCO<sub>3</sub>/non-CO<sub>3</sub> phases, as confirmed by NEXAFS spectra. These findings suggest that biomineralization in the fungal micro and nanoenvironment is influenced by localized physicochemical and metabolic conditions that shape mineral phases. C NEXAFS spectra further supported the Ca data, showing C-specific spectral features in the calcite-rich regions across all samples. This underscores STXM's capability to resolve complexities and mechanisms of fungal CaCO<sub>3</sub> formation (e.g., mineral phase composition, fungal organic-mineral interactions, and spatial heterogeneity). Overall, this study provides critical nanoscale insights into fungal CaCO<sub>3</sub> precipitation, thus providing valuable guidance in optimizing fungal systems in self-healing concrete applications. </p>}},
  author       = {{Tuyishime, J R Marius and Hammer, Edith C and Pla-Ferriol, Martí and Thånell, Karina and Alwmark, Carl and van Velzen, Sophie and Floudas, Dimitrios and Platakyte, Rasa and Obst, Martin and Zou, Hanbang}},
  issn         = {{1944-8244}},
  language     = {{eng}},
  month        = {{07}},
  number       = {{26}},
  pages        = {{37648--37656}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{ACS applied materials & interfaces}},
  title        = {{Nanoscale Characterization of Fungal-Induced CaCO3 Precipitation : Implications for Self-Healing Concrete}},
  url          = {{http://dx.doi.org/10.1021/acsami.5c07137}},
  doi          = {{10.1021/acsami.5c07137}},
  volume       = {{17}},
  year         = {{2025}},
}