Cyanobacteria as an eco-friendly bioresource for EPS production with crack healing capacity in concrete

Abstract

Cyanobacteria, alike microalgae, are photosynthetic microorganisms found in different environmental conditions. These photosynthetic bacteria are also considered promising solutions for cracking problem in concretes. These photosynthetic organisms precipitate CaCO3 crystals in concrete microcracks and pores, thus sealing the cracks and increasing the strength gain of the concrete blocks. Cyanobacteria Lyngbya sp., Phormidium sp., and microalgae Chlorella vulgaris were studied initially. Lyngbya sp., Phormidium sp., and Chlorella vulgaris have the additional property of secreting the exopolysaccharide (EPS). EPSs are an important class of biopolymers with great ecological importance. Because of their high charge density and capacity to act as mineralization nucleation sites, cyanobacterial exopolysaccharides are currently receiving more attention. Using the three strains stated above, this study investigates the impact of physiochemical factors on biomass concentration and exopolysaccharide synthesis and creates mathematical models. Using Central Composite Design (CCD), it is possible to study the interactions between the many parameters, including nitrate concentration, starting media pH, light intensity, and temperature. The biochemical characteristics of the leftover biomass are assessed after exopolysaccharide extraction, and because of its high carbohydrate and fat content, it can be used to produce biofuel. The study of checking the microbial crack healing capacity and strength gain of the concrete using these three cyanobacterial strains is being studied. Based on the outcome, the best species was chosen. Further microstructural analyses, such as X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to support the calcium carbonate precipitation.