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

Abstract

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.