Novel bio-fertilizer based on nitrogen-fixing bacterium immobilized in a hydrotalcite/alginate composite material

The bacterium Streptomyces sp. is a common genus of the actinomycetes class found in soils and rhizospheres. This bacterium can produce substances with bio-stimulant capacity through the fixation of nitrogen from the air. In this work, the Streptomyces sp. bacterium was immobilized on a ZnMgAl-hydrotalcite clay and embedded in calcium alginate beads to generate a novel bio-composite that functions as a bacterial reservoir and as a controlled release material for bacteria to be used as a bio-fertilizer.The results showed that the novel bacterium-hydrotalcite/alginate bio-composite was very efficient as a bio-fertilizer showing a plant length of 64 mm in only 14 days of growing, which corresponds to an increase of ca. 760% in the lettuce plant growth in comparison with the materials without bacteria. In short, the present results demonstrate that the hydrotalcite and alginate served as an excellent container to keep the bacteria alive, providing nutrients to them and controlling their delivery.