Screening Of Silicate Bacteria And Its Application In Biological Desilication

One strain of GSY which can remove more silicate was isolated and identified through biochemical and physiological characteristics and 16S rDNA sequence analysis. The strain was identified as Bacillus mucilaginosus, and it could improve the ratio of Al₂O₃ to SiO₂(A/S) in the samples from 2.86 to 5.07 at pH 7.2, 30℃, 200 rpm, for 7 days. The strain of GSY was mutagenized by N⁺ implantation. Implanting ion energy was 10 KeV, and implanting does ranged from 4.0×10¹⁵ ions/cm² to 5×10¹⁶ ions/cm². The effect of mutagenesis is significant, but the genetic stability of GSY is poor.The morphological characteristics of GSY were different between nitroge medium and four selected nitroge-free medium. The efficiency of desilication is determined in the four fermentation culture medium containing nitrogen source. The result showed that GSY can liberate silicon from silicate minerals in the four medium efficiently, but less efficiently than in nitroge-free fementation medium. The optimization of culture medium composition is determined on the basis of Ashb medium without nitrogen source, the result showed that the optimum nitrogen and carbon source were respectively urea and lactos.To further enhance the strain's capacity of desilication, single-factor experimental design and response surface were used to optmize the dose of carbon and nitrogen in fermentation medium. The result shows that 10.35 g/L urea and 12.60 g/L lactose can improve the ratio of Al₂O₃ to SiO₂(A/S) in the samples from 2.86 to 5.67, and the confidence level is 91.79%. The polysaccharides were extracted from the Silicate bacteria fermentation culture. The purity of the extracte were determined using characteristic color reaction and UV spectrophotometric method, result showed that it didn't contain any proteins and amino acids.The polysaccharides structures were analyzed by infrared spectrum(IR), the absorption peak of typcal polysaccharides were observed. A Sephadex G-50 gel filtration chromatographic column has been used for the isolation of the polysaccharides. The test shows that it only has one kind of polysaccharide. Leaching test shows that 100mL, 100μg/mL of polysaccharide solution can improve the ratio of Al₂O₃ to SiO₂(A/S) in the samples from 2.86 to 4.19. In addition, 100 mL, 10 g/L of bacterial suspension and 100 mL fermentation liquid can improve the ratio of Al₂O₃ to SiO₂(A/S) in the samples from 2.86 to 3.32 and 3.74.Whether polysaccharides and pure cultures interact with silicate minerals were analyzed by FTIR. The results showed that the apices of 1070 cm^-1 in the FTIR of polysaccharides and pure cultures are very similar. According to the literature statement they form complexes with silicon in the form of Si—O—R.The surface change of silicate minerals before and after dealing with leaching were studied by the changes of elements by XREDS and scanning electron microscopy(SEM). According to scanning electron microscope- energy dispersive X-ray analysis, the effect of dissolution is significant.