Living sand: Microbial nanocellulose and chitin-rich mycelia enhance granular material properties

Natural fibers, principally those formed of polysaccharides, are critical to impart adequate mechanics and water dynamics to soils. In this study, we hypothesize that fiber producing microbes such as bacterial nanocellulose and mycelium could induce life into granular materials, with the potential to reduce erodibility while improving water retention. Herein, the structures formed from the growth of such aerobic microbes in the porous network of sand granules are studied. This approach introduces both organic matter and microbial biomass, which we show can dramatically enhance water retention and cohesion between sand grains. Ex-situ prepared bacterial nanocellulose sheets were also evaluated for their ability to reduce water permeability and to act as geotextiles when layered into sand. In addition, two mycelium producing strains were also evaluated for their in-situ growth. In total, three strains were studied: two mycelium producing strains (Schizophyllum commune Empa strain 750, Schizophyllum commune strain H-48a), and one nanocellulose producing bacterium (Komagataeibacter medellinensis). The microstructures formed were studied by scanning electron microscopy and the growth kinetics evaluated across microbial systems. Overall, we show that the use of polysaccharides producing microbes can form bio-integrative structures with a porous granular media such as sandy soils.