Biosolubilization Of Low-grade Rock Phosphate By Microbial Consortia

There is abundant of rock phosphate resources in China,but most of them are mid-low grade rock phosphate.In recent years,with the large consumption of rock phosphate concentrates,the development and utilization of mid-low grade rock phosphate have been paid more and more attention.Due to the problems of long process flow,high production cost and serious environmental pollution in traditional beneficiation methods,the development and utilization of low-grade rock phosphate is limited.Based on cost reduction and protection of the ecological environment,the application of microbial technology in the development and utilization of low-grade rock phosphate has gradually attracted the attention of researchers.In this paper,microbial solubilization of low-grade rock phosphate as the masterstroke,and the following three aspects are studied.It provides a theoretical basis and technical support for solving the problem of scientific utilization of China’s abundant low-grade rock phosphate resources.1.Microbial community structure in biosolubilization of low-grade rock phosphate by microbial consortia from phosphate mineThe soil and sludge samples from phosphate mine were used as the source of the microbial consortia,and the enrichment and domestication of the two media were utilized.At the same time,four microbial consortia were obtained,and their solubilization effects on low-grade rock phosphate were studied.The results showed that under the same culture conditions,the domesticated soil consortia enriched by National Botanical Research Institute’s phosphate growth medium（NBRIP medium）had the strongest capability of phosphate solubilization.Phosphate content can reach500 mg/L in the medium with enough nutrients,the microbial consortia with different structures has different effects on low-grade rock phosphate.The microbial species and components in the culture medium will also change greatly during different culture periods.This change largely determined the bacterial group dissolution effect,under the action of microbial consortia,the rock phosphate surface was changed.A FT-IR analysis showed that the higher the intensity of the absorption peak at3400-2500 cm^-1,the higher content of soluble phosphate in the culture medium.2.Biosolubilization of low-grade rock phosphate by different types of microorganismsBy separating and purifying four microbial consortia,four strains of single bacteria with strong phosphate solubilizing capabilities were obtained.The combined rains were obtained by free combination of single strain,and the difference of the phosphate solubilization effect of the homologous consortia,the combined strains and the single strain was compared,and the simple culture medium was optimized for the combined strains.The results showed that the original microbial consortia had obvious advantages over the single strain and had good phosphate solubilization effect and duration.The microbial consortium was 50%higher than the combined strains.It can be seen that the phosphate solubilizing action of the combined strains that the more kinds of phosphate solubilizing strains,the phosphate solubilizing effect is not necessarily good.When sucrose was used as the carbon source and urea was used as the nitrogen source,the maximum dissolved phosphate reached 200 mg/L by the combined strains,and the overall increase was about 60%.3.Preparation of microbial sustained-release sodium alginate microspheres and their biosolubilization of low-grade rock phosphateNBRIP mineral soil consortium with strong phosphate solubilizing capability was selected as experimental strain.Sodium alginate microspheres were prepared by sharp-hole method as carrier.At the same time,by adding porogen or chitosan coating optimization,a better preparation method of microbial-loaded sodium alginate microspheres was explored.Finally,the phosphate solubilizing effect and effective time were verified.Results showed that the effects of sodium alginate microspheres with different particle sizes were quite different.In the range of 2-3.3 mm,the smaller the particle size,the better of the phosphate solubilizing effect.The types and dosage of porogen will affect the sustained release and phosphate solubilization of microspheres.The effect of sodium bicarbonate as porogen is better than that of calcium carbonate.The optimum addition of sodium bicarbonate is 0.15g when the particle size of the microspheres is 2mm.The performance of the microspheres will be improved by adding chitosan twice.Orthogonal experiments showed that the microspheres with sodium bicarbonate as porogen and chitosan as secondary coating had the best effect.Microbial viability and sustained release can be achieved through the loading of microspheres,which could effectively maintain the number of viable bacteria in the culture medium,increase the amount of phosphate dissolved and prolong the effective time.