Prospects to Enhance Biological and Mechanical Performance in Living Building Materials

Living building materials (LBMs) are produced by integrating viable microorganisms into inert structural scaffolds. Our framework takes advantage of microbially induced calcium carbonate precipitation (MICP) and has potential for recycling and self-healing, features that depends on the microorganism survival under LBM dehydrated conditions. Cyanobacteria is exposed to desiccation stress under nonaquatic ambient conditions. By introducing a desiccation protectant, the small sugar trehalose, LBMs cells were able to survive in the dried state for several days, with no negative effect on mechanical properties. We genetically engineered Synechococcus 7002 strains to synthetize trehalose, by introducing treZ and treY genes from Anabaena sp. PCC 7120, a moderate desiccation tolerant aquatic organism, under regulation of two strong promoters, a native constitutive and an IPTG inducible. Our novel LBM is composed of sand, hydrogel (gelatin) for binding aggregates, and live bacteria, capable of inducing calcium carbonate precipitation. Cyanobacteria has been shown to induce precipitation of calcite, dependent on photosynthesis, with the advantage of capturing and storing CO₂. Comparison between biotic and abiotic MICP show greater structural properties, especially superior fracture energy for biotic MICP samples. Autotrophic and heterotrophic bacterial MICP pathways, through either ureolysis or photosynthesis, were successful in mechanically enhancing the LBM, including material compression strength and flexural energy. We also tailored several LBM design factors in an effort to expand the multifunctionality of our building materials. This study shows that LBMs are an exciting new class of materials with a range of features that can be tailored for adaptation to the in-service application. This project is funded by DARPA: Engineering Living Materials Program.