Abstract:
Microbial induced carbonate precipitation (MICP) through the ureolysis metabolic
pathway is one of the most studied topics in biocementation due to its high efficiency. Although
excellent outcomes have proved the potential of this technique, microorganisms face some
obstacles when considering complicated situations in the real field, such as bacterial adaptability
and survivability issues. This study made the first attempt to seek solutions to this issue from the
air, exploring ureolytic airborne bacteria with resilient features to find a solution to survivability
issues. Samples were collected using an air sampler in Sapporo, Hokkaido, a cold region where
sampling sites were mostly covered with dense vegetation. After two rounds of screening, 12 out
of 57 urease-positive isolates were identified through 16S rRNA gene analysis. Four potentially
selected strains were then evaluated in terms of growth pattern and activity changes within a
range of temperatures (15°C–35°C). The results from sand solidification tests using
two Lederbergia strains with the best performance among the isolates showed an improvement
in unconfined compressive strength up to 4–8 MPa after treatment, indicating a high MICP
efficiency. Overall, this baseline study demonstrated that the air could be an ideal isolation
source for ureolytic bacteria and laid a new pathway for MICP applications. More investigations
on the performance of airborne bacteria under changeable environments may be required to
further examine their survivability and adaptability.
