| Potassium is one of the important elements in vital movements and it has many important functions in maintaining plants' nutrition. Soluble potash resources is very lack in China, so research on release of potassium from potassium-bearing minerals or rocks is important to mitigate the lack of potassium fertilizer resources, which is of great significance both in theory and in practice. In the paper, the bioconversion to potassium-bearing mineral by the facultative thermophiles Aspergillus fumigatusTH003 was studied in order to increase biological availability of potassium-bearing mineral.The results of research showed mechanical action exists between mycelia and mineral particles turnning to the revolution of shaker and the mechanical action was affected by strength of revolution action and the addition of mineral powder. Mechanical action could strengthen when strength of revolution action or addition of mineral powder increased. In the cultural system (containing 100 mL of liquid medium and 5 g of shale powder were mixed into 250 mL triangular flasks), mycelia can adsorbed mineral particles and the adsorption action correlate with biomass. Adsorption action to mineral powders by mycelia strengthened along with the biomass increased. Biomass reached up to the maximal value (11.02g/L) when the carbon source was glucose, at the same time, the amount of adsorbed mineral powder also reached up to the maximal value (14g/100mL) . Analogously, biomass reached up to the maximal value (10.86g/L) when the nitrogen source was corn-steep, at the same time, the amount of adsorbed mineral powder also reached up to the maximal value (13g/100mL). The mycelia degraded mineral powders in the progress of static state culture and dynamic state culture, but bioconversion action in dynamic state culture was stronger than in static state culture. The highly available potassium (HAP) reached up to 104.2 mg/L when the cultural time was 24 days in the progress of static state culture, but in the progress of dynamic state culture, the HAP reached up to 335.0 mg/L when the cultural time was 18 days. In addition, the progress of dynamic state culture was also the direct weathering progress. When mineral particles were wrapped with a membrane with 0.22μm pore, minerals were in indirect contact with fungi and weathering of mineral particles may be the chemical degradation by the metabolite of mycelia and the maximal value of HAP only was105.4mg/L after 22 days. In the progress of dynamic state culture, the weathering process includes the adsorption, absorption and encapsulation to mineral particles by mycelia, the formation of organic-mineral complex, the etching toward minerals by mycelia and the chemical degradation by fungi metabolite. Optimum conditions of shake flask fermentation was obtained by using Central Composite Rotatable Design (CCRD) and the mathematic model was yielded by using the analysis system of Design Expert software on account of the results of one way experiments. Based on the mathematic model, value of HAP reached up to maximal value (414.6 mg/ L) when the value of glucose, corn-steep, initial pH, temperature, treatment time, rotary speed and inoculum were 39.5 g / L, 14.9 g / L, 5.6, 46.2℃, 18.9 d, 98 rpm and 10.2 % (V/V). The mathematic model could be employed to direct practice. The results of solid static fermentation showed conversion ratio of potassium reached up to 2.86% when waste material cultured Flammulina velutipes was major material in the solid medium and the method of noncontinuous ventilation fermentation was employed to carry out.In the paper, the process and mechanism of bioconversion to potassium-bearing minerals by microorganism were studied, which could supply evidences of the field in the world. Theory and method of fermentation engineering were employed to apply in the field of bioconversion to potassium-bearing minerals and the results were important groundwork in research new type technique of processing potassium-bearing minerals and expanded the application category of microbe-geochemistry. |
