Biotransformation Of Biotite And Its Mechanism

China is a large agricultural country, and the development of agriculture is depend on fertilizer, in which potash fertilizer is account for a large proportion. Potassium plays vital role on the growth of plants who can improve the strength of photosynthesis, promote crop formation in vivo starch and sugar, enhance crop resistance, and improve the absorption of nitrogen. Our reserve of soluble potash is only 2% of the world total. Potash fertilizer accounted for only about 50% in self-sufficiency. But the reserves of low-grade potash is very impressive, in whlch biotite is one category. Because of low energy consumption and environmental pollution, microbial transformation has attracted widespread attention. But correlational studies was focused on strain screening and its effect of potassium releasing, weathering mechanism and its applying. And about how to effectively improve the conversion efficiency of potassium release is rarely research. Bacillus mucilaginosus and Aspergillus niger are common soil microbes, they can take advantage of the decomposition of insoluble mineral in soil for their growth and reproduction, while also promoting the biogeochemical cycling of soil mineral elements. Many studies were used these two strains as mode in studying microbe-mineral interaction.In this study, I separately cultured B. mucilaginosus and A. niger in nitrogen-containing medium and czapek’s medium, in which biotite was the source of potassium. After 5 days culture in, the concentration of various ions in both of the two cultures, surface morphology of biotite, pH, content of organic acids and CA activity were detected by ICP-OES, SEM, HPLC and a specific method for the determination of CA activity. The results showed that, B. mucilginsus and biotite tightly adhered together to form bacterial-mineral complex through some sticky substance, such as polysaccharides. But the fungal hyphae wrapped biotite and formed fungus-mineral aggregates. Overall, the released ions in fungal culture were higher than those in the bacterial culture, among which Al3+、 Fe3+and K+were higher than about 17,30 and 3mg/L. And the amount of acidic substance and CA activity in the fungal culture were both significantly higher than the bacterial culture as well. So, we confirm that A. niger has a more powerful mineral weathering capacity. So, A. niger was used in follow-up study.In further, detecting the expression of cysteine synthase (CysM),Na+/K+-ATPase, citrate synthase (CS), fatty acid synthase subunit alpha (FAS2) glutathione S-transferase (GST), tryptophan synthase alpha chain (trpA) pyruvate carboxylase (PC), carbonic anhydrase (CA) by RT-qPCR when A. niger was cultured under different minerals. We found that the expression level of Na+ /K+-ATPase gene in experimental group was higer than the control in all of potash group, magnesite group and phosphate group. And the expression of other genes were different. In potash group and magnesite group, CysM, trpA and PC were up-regulated, the expression of other genes is almost the same. And in phosphate group, the expression of all of the seven genes were no siginificant difference. Those results showed that A. niger can regulate its gene expression to overcome the deficiency of soluble nutrients. And facing different minerals, A. niger can differentiate regulate gene expression to accommodate different nutritional conditions or living environment.In order to improve the conversion efficiency of potassium from biotite, we explore the effect of phytic acid, GA and Tween on the weathering of biotite by A. niger. The results showed that phytic acid can effectively increase the amount of elution of potassium. To reduce costs, using phytic acid crude fluids-rice bran broth instead of phytic acid, the results showed that compared with not adding rice bran broth, addded rice bran in A.niger fermentation medium increased the amount of elution of potassium above about 70mg. In order to further improve the conversion efficiency of potassium, we leached biotite through the integrated application of chemical extraction methods, and A. niger extraction method, and explores the adsorption of heavy metals by the biotite after extraction performance. We can see that applying 11% H2SO4 solution can effectively extract potassium.A. niger was not able to release more potassium, but it released silicon-constituent element of the skeleton structure of biotite. This provides a new idea for using low-grade potash and producing potash fertilizer in our country. Meanwhile, the structure of biotite changed after extraction, they showed the ability of Cd fixing, which is important in decreasing the bioavailability of heavy metals in agricultural soils.Currently, Study of the microbial conversion of K-bearing rock is still at the primary stage. It is still a bottleneck about how to achieve efficient conversion of potassium. Expanded in-depth research in this area has both the academic value and economic value.