LDH/SBA-15 nanocomposite containing nitrogen-fixing bacteria as an efficient biofertilizer

Nitrogen from air can be available for actinobacteria microorganisms having the ability to reduce nitrogen to ammonia for plant growth promotion. In this work, a nitrogen fixing bacterium of the genus Streptomyces sp. was immobilized in an LDH/SBA-15 nanocomposite to generate a bio-nanocomposite able to promote the growth of lettuce plants. The bio-nanocomposite was formed by impregnating the bacterium on a material composed of layered double hydroxide (LDH) nanoparticles homogeneously distributed over the external surface of the SBA-15 component forming a spongy agglomerates with sizes ranging from 0.5 to 2 µm. The bio-nanocomposite with a specific surface area of 375 m2/g was very effective since the lettuce plants achieved a length of 36 mm in only 14 days, while the individual LDH and SBA-15 materials, with or without microorganisms, were almost inactive. The high effectiveness of the novel bio-nanocomposite was attributed to the mode of LDH dispersion over the SBA-15 surface, which leads to weak microorganism-inorganic materials interactions, and to the LDH contribution to the bacteria nutrition.