Integrated Use of Maize Bran Residue for One-Step Phosphate Bio-Fertilizer Production

The development of bio-fertilizer inoculants is important and desirable. Two phosphate-solubilizing Bacillus subtilis strains were inoculated onto maize bran residue (MBR), which was used as bio-fertilizer carrier and a primary source of nutrients in a medium used for semi-solid fermentation. Water holding capacity, swelling capacity, scanning electron microscopy, and shelf-life assays demonstrated that ground MBR had satisfactory properties for a bio-fertilizer carrier. The maximal soluble phosphorus (P) reached 642.7 ± 0.43 mg l^-1 in an orthogonal test under the following optimal conditions: a pH of 7.0, a cultivation temperature of 31 °C, a medium water content of 160%, and a filling capacity of 500 g l^-1. The bio-fertilizer produced by MBR improved the growth of wheat (Triticum aestivum L.) and Chinese cabbage (Brassica rapa pekinensis) with respect to plant height (by up to 18.36%) and the lengths of roots (by up to 34.03%, 27.22%, separately) in a pot experiment. This study integrated the production and storage of a bio-fertilizer to realize the one-step production of a solid bio-fertilizer using MBR.