Biomineralization Induced by Colletotrichum acutatum: A Potential Strategy for Cultural Relic Bioprotection

Abstract

Colletotrichum acutatum is a fungus capable of biomineralization reported in our previous study. In this paper, we compared the ability of this fungus to induce mineralization under different calcium sources, pH levels, and differing carbon availability. Here we found that organic acids, the alkalinity of the environment, and low carbon conditions were major factors influencing calcium carbonate precipitation. High performance liquid chromatography showed that citric acid was a metabolite produced by C. acutatum, and that other organic acids including formic, propionic, α-ketoglutaric, lactic, and succinic acids can be used by this fungus to promote CaCO3 formation. Based on these findings, the mechanism of the biomineralization induced by C. acutatum should be divided into three processes: secreting organic acid to dissolve limestone, utilizing the acid to increase the alkalinity of the microenvironment, and chelating free calcium ions with extracellular polymeric substances or the cell surface to provide a nucleation site. Interestingly, we found that hydroxyapatite rather than calcium carbonate could be produced by this fungus in the presence of phosphate. We also found that the presence of acetic acid could inhibit the transformation of vaterite to calcite. Further, we evaluated whether the proliferation of C. acutatum could influence the deterioration of stone relics. We found that low carbon conditions protected calcium carbonate from dissolution, indicating that the risk of degradation of limestone substrates caused by C. acutatum could be controlled if the fungi were used to consolidate or restore stone monuments. These results suggest that C. acutatum-induced biomineralization may be a useful treatment for deteriorated stone relics.

Microbe‐Mediated Extracellular and Intracellular Mineralization: Environmental, Industrial, and Biotechnological Applications

“…The EPS consist of high‐molecular‐weight polysaccharides and proteins, as well as macromolecules such as DNA, lipids, and humic substance secreted by the microbes as natural polymers. The EPS have a strong correlation with nucleation [ 135 ] because of the presence of polysaccharides and proteins that contain carboxyl, phosphate, amine, and hydroxyl groups. [ 136 ] They play an important role in microbial mineralization by sequestering metal cations via binding to those charged groups.…”

“…This process prevents the degradation of CaCO 3 and may be used for preservation of deteriorated stone relics. [ 135 ] Calcium carbonate precipitation induced by Cupriavidus metallidurans , a Gram‐negative, motile, non‐spore‐forming, rod‐shaped bacterium known for its ability to resist toxic heavy metals, may be used for the restoration and preservation of ornamental stones by deposition of a compact vaterite layer on the marble substrate. [ 290 ]…”

An indigenous inland genotype of the black yeast Hortaea werneckii inhabiting the great pyramid of Giza, Egypt

“…The ability of the isolated fungi from the mentioned examples to dissolve calcium carbonate has been reported (e.g., genera Aspergillus, Aureobasidium, and Cladosporium; Trovão et al, 2020 ; Santo et al, 2021 ) that confirmed their ability to damage and affect stone structures. Fungus-assisted degradation of limestone initiated with the secretion of organic acids to dissolve the stone substrate and increase the alkalinity of the microhabitat, then produce extracellular polymeric substances to chelate-free calcium ions in a process known as biomineralization (e.g., fungus Colletotrichum acutatum ; Li et al, 2018 ). In some reports, the biomineralization of cultural heritage sites by fungal biofilms was reported to contribute to the rock coating development ( Gadd and Dyer, 2017 ).…”

Escherichia colitemplated iron oxide biomineralization under oscillation

“…[4][5][6][7] BCM has found wide applications in electrode materials, sewage treatments, ecological restoration, cultural relics restoration, nano-drug carriers and cancer treatments. [8][9][10][11][12][13] Due to the importance of biomineralization in both basic theories and practical applications, biomimetic mineralization attracted attentions of scientists from a broad range of disciplines including biology, chemistry, and materials science. These researches are mainly focused on roles of cell components or compositions in templating or regulating biomimetic mineralization 14 and fall into two categories of mineralization systems, that is, in vitro mineralization under functions of specic biomolecules or in vivo mineralization promoting by intact cells or organisms.…”