Exploring filamentous fungi for survival and biomineralization in concrete

Concrete is the second most widely used material in the world after water, consuming large amounts of natural resources like limestone, gravel, and sand. The global production of cement, which is the key ingredient for concrete, is responsible for around 1.6 billion metric tons of carbon dioxide, one of the top three sources of anthropogenic CO2 emissions. Reducing the carbon and material footprint of concrete while meeting global demand is therefore a major challenge. Recently, the usage of microorganisms has emerged as an area of increasing interest for an eco-friendlier concrete industry. For instance, microbial-induced calcium carbonate precipitation (MICP) in traditional concrete can improve the durability or recyclability of concrete. A prerequisite for this is detailed knowledge of the behaviour of microorganisms in concrete. In this study, we investigated the tolerance of three filamentous fungi – Trichoderma reesei, Aspergillus niger, and Mortierella alpina - towards different concrete compositions and evaluated their biomineralization potential. T. reesei had high expression levels of genes associated with MICP pathways and corresponding enzyme activities. Embedding in concrete revealed that T. reesei survived in up to 8% cement content. Hyphal-associated calcium deposits were visualized using Alizarin Red S staining, and SEM–EDX analysis indicated calcium- and carbon-rich mineral signatures consistent with calcium carbonate-like phases. Together, these findings provide a systematic evaluation of fungal survival in concrete and contribute to a better understanding of the biological feasibility of T. reesei in concrete environment.