Convertion Of Spent Mushroom Substrate To Biofertilizer Using Co-inoculation Of Salt-and Alkaline-tolerant Phosphate-solubilizing Fungus, Potassium Solubilizing And Nitrogen Fixing Bacteria

Potassium-solubilizing microorganism K3and N2-fixing microorganism N1were isolated from farm waste compost （FWC）. K3showed high insoluble potassiumsolubilization ability, which was4.10mg/L. N1also showed high N2-fixing ability,which was1.81×10^-2mol/L. Based on the combination of morphological classificationand sequence analysis of16S rDNA, K3and N1were respectively identified asBacillus and Azotobacter chroococcum. K3and N1showed great resistance againstdifferent environmental stresses like55℃,14%NaCl concentration,1.2mol/L NH4+concentration, pH5-9condition and50℃,11%NaCl concentration,0.8mol/L NH4+concentration, pH4^-10condition, respectively. These results showed that two strainswith good tolerance had more application.Strain FL7was cultivated in the optimal medium to study the relationshipsbetween P solubilization, pH and organic acid production.852.8mg/Ltotal organicacids can be produced and pH can be reduced to3.8after60h, meanwhile, the solublephosphate content reached816.16mg/L. This finding suggested that pH decrease hada positive correlation with the insoluble P solubilization. Organic acids could result inpH decline, which proves that the production of organic acids is an importantmechanism for solubilizing Ca3（PO4）2. HPLC analysis showed that P. farinose FL7produced acetic and succinic acids in the culture medium containing glucose as thesole carbon source （Table5）, which is consistent with the report of Fomina et al.（2004） that secretion of succinic acid and acetic acid by the majority of fungal strainsduring solubilization of zinc P and pyromorphite.Optimization of medium compost and fermentation conditions were studied, amaximum sum biomass of48.87×10⁸cfu/g predicated by the model equation wasachieved at water content74.8%and rotational speed231rpm. Subsequentexperiment demonstrated48.62×10⁸cfu/g biomass could be reached, which contained2.4×10⁸cfu/g FL7,25.22×10⁸cfu/g K3,21×10⁸cfu/g N1.Biofertilizers with spent mushroom substrate as the carrier were testified by potexperiments, SMS biofertilizer produced by P. farinose signifcantly improved thegrowth of soybean. The available P was all above200mg P kg^-1soil for ten different soils tested with the addition of the biofertilizer. Biomass of strain FL7after theexperiments were also measured, the results showed the strain FL7could increase to210⁶cfu/g soil, suggesting it can survive well in soils under the testing conditionsand dissolve the insoluble phosphorus. Available P in soils was significantly increased.Therefore, strain FL7can play an important role in improving P bioavailability. Theresults also showed that the P. farinose biofertilizer signifcantly improved the wholedried plant weight. A noteworthy observation from this result is that the similarimprovement of plant growth was achieved by using biofertilizer with or withoutinsoluble P, indicating the biofertilizer could be used alone with high efficiencywithout extra insoluble P.SMS biofertilizer produced by three microorganism also improved the growth ofsoybean. The available P, K was above359mg P kg^-1soil and1200mg K kg^-1soilrespectively for soil tested with the addition of the biofertilizer. The total N was100mg N kg^-1soil soil more than the soil without biofertilizer addition. The resultindicated the biofertilizer could dissolve insoluble P, K, and fix N2very well.