From ureolytic limitations to mycelial paradigms: A critical review of actinobacteria-mediated self-healing in cementitious composites

The object of research is the transition from conventional ureolytic biomineralization to Actinobacteria-mediated self-healing paradigms in cementitious composites. The purpose of this work is to analyze the physiological, metabolic, and structural advantages of natively alkaliphilic Actinobacteria, specifically Streptomyces species, as an alternative to conventional strains that generate hazardous ammonium byproducts and require complex encapsulation. Method. A comprehensive bibliometric analysis and systematic literature screening were conducted to evaluate microbial agents, metabolic pathways, delivery systems, and mechanical recovery metrics. The methodology encompassed the extraction and synthesis of quantitative and qualitative findings from peer-reviewed literature to compare conventional ureolytic methods with emerging Actinobacteria-mediated paradigms. Results. The analysis reveals that natively alkaliphilic Actinobacteria possess inherent physiological adaptations that eliminate the requirement for chemical neutralization or synthetic carriers, with robust endospores ensuring long-term viability within high pH environments. Crucially, the three-dimensional mycelial networks of these filamentous microorganisms' function as autonomous structural scaffolds, guiding uniform calcite crystallization and physically bridging wide cracks without inducing localized clogging. Furthermore, non-ureolytic metabolic routes, such as organic acid degradation, facilitate ammonia-free biomineralization, while concurrent Polyketide Synthase (PKS) gene cluster activity synthesizes antimicrobial compounds, offering a dual-functional mechanism that seals voids and prevents biodeterioration. Despite these advantages, significant knowledge gaps persist regarding genome-resolved metagenomic profiling of Polyketide Synthase pathways and the extended mechanical stability of calcite-mycelium composites. Future research must transition from descriptive taxonomic profiling to targeted metabolomic analyses and macro-scale validation. The proposed integrative framework, converging inherent alkaliphily, mycelial scaffolding, and non-ureolytic biomineralization coupled with polyketide-mediated antimicrobial defense, establishes a foundational methodology for developing autonomous, environmentally benign, and structurally robust bioengineered infrastructure.

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