Preliminary Study On Thermostable And Inorganic Phosphorus-Solubilizing Microorganisms In Composting

Composting, as one of the main treatment of municipal solid waste resource utilization, has been widespread concern in society, but because of selective compositions in the garbage and lack of appropriate composting technology, which results in many problems, such as higher costs of operation and management, long compost fermentation cycle and products with low content of nutrient elements. This has seriously hampered the promotion and application of composting technology in China. Based on this, this study will focus on inoculating efficient high-temperature solubilizing inorganic phosphorus bacteria, study its characteristics and the growth of dynamic characteristics, and through the best ratio of solubilizing compound agents and solubilizing conditions optimization, to enhance the activity of compost inoculated with agents to promote the conversion of insoluble phosphate, the phosphorus-rich organic compost.To improve conversion efficiency of the phosphorus content and the insoluble phosphate, we selected nine high-temperature solution of inorganic phosphorus (P1, P2, P3, and P4, P5, P6, P7, P8and P9), using qualitative and quantitative analysis, methods, studied its solubilizing ability. The results showed that after being cultured for96h, dissolved phosphorus circle ratio (D/d) of P2is up to2.12. But the quantitative determination in liquid culture, total dissolved phosphorus of P2is only10.95μg/mL. At the same time dissolved phosphorus of P5is the strongest,66.98μg/mL, its dissolved phosphorus circle ratio (D/d) is much smaller than the P2. Indicating that there are some limitations using qualitative analysis to observe phosphate solubilization circle; quantitative analysis in liquid culture may be a more reasonable approach.By the determination of the total available phosphorus in the fermentation broth, which select phosphate rock as the only source of phosphorus. Three strains of the thermophilic phosphate solubilizing microorganisms named P3, P4, P5, screened and domesticated in previous experiments, were selected and mixed as complex bacteria combination according to Simple-centroid method with Design Expert software. The analysis results about the7level of experiment showed that the total available phosphorus of the forth combination (P4:P5:P3=0:50%:50%) is241.70μg/mL, significantly higher than other complex functional strains. Analysis of variance reached a significant level indicated that the strains in the forth level can be mutually reinforcing and symbiotic collaboration.Then Quadratic polynomial mathematical model of the solubilized-phosphorus condition of thermophilic compound bacterium was established by response surface methodology (RSM). Based on the design of Box-Behnken to optimize the optimal levels and the interaction of five important factors which including the incubation time(x1)、the incubation temperature(x2)、pH(x3)、the content of rock phosphate(x4)、the inoculum size of microorganism(x5). The results showed that the optimized result of the solubilized-phosphorus condition of thermophilic compound bacterium was that the incubation time should be7.18days, the incubation temperature should be49.98℃, pH value should be6.63, the content of rock phosphate added in the culturing medium should be6.21g/L, and the inoculum size of microorganism should be6.07%. In this condition, the theoretical value of solubilizing amount is257.93μg/mL, which is higher than that of the combination of any two factors. This indicates that the solubilizing amount is impacts by many factors, only when the solubilizing conditions are the optimal values, the composite agents have a maximum solubilizing amount.Microbial phosphate solubilization mechanism depends first on the characteristics of the microorganism itself, such as secretion of protons, organic acids and other substances in quantities and types. In this study, by analysising the correlation of solubilizing microorganisms dissolved phosphorus content and pH, the bacterial number, the results show that:after being cultured8d, the significantly negative correlation is found between dissolved phosphorus content and pH values of solubilizing strains (P1, P2, P3, P4, P5, and P9), the significantly positive correlation is found between dissolved phosphorus content and the bacterial number of solubilizing strains (P3, P4, P5, P7and P9).Amplify16S rDNA and ITS region of Solubilizing strains by PCR, sequencing results showed that:solubilizing bacteria P1belongs to Bacillus, while the rest of the eight kinds of solubilizing fungi belong to Aspergillus, all of the similaritys are above99%.By the identification of phosphate-solubilizing strains, better reveal the relationship between strains of solubilizing strains with other features strains in composting, at the same time provide a theoretical basis for fluorescent labeling solubilizing strains, in order to reveal the community structure changes and bacterial number increase or decrease with time of the solubilizing strains inoculated into the composting.