Biochemical Analysis of Microbial Adsorption Behavior on Iron and Steel Slag Using DNA-specific Fluorescent Reagent, and the Effect of Microbial Biofilm Attached to Slag on pH Buffering Action

Abstract

To evaluate microbial potentials for the material development of iron and steel slag, this study particularly investigated the chemical effect of slag, which was artificially coated with a microbial biofilm, on buffer action. Prior to evaluating the slag, this study also developed a method to determine the amount of microbes adhering to slag. To encourage the growth of Bacillus bacteria on slag, the slag was mixed with the bacteria in LB medium for 24 hours. After extracting microbial DNA using the hot-alkaline DNA extraction method, the microbial quantity attaching tightly to slag was determined from the concentration of the microbial DNA using Pico Green-based fluorometry. The adsorption isotherm between the microbial quantity attached to the slag and the corresponding reacting microbial amount was analyzed using the Langmuir and Freundlich adsorption models. To examine the buffering action of slag coated with and without microbes, each slag was immersed in distilled water for seven days. Next, both pH levels of each slag-containing solution and each amount of microbes attached to slag were determined. The pH increased in both solutions containing slag coated without biofilm and with partially desquamated one; in contrast, the slag coated with well-preserved biofilm showed a buffering action, resulting in an inhibited increase in pH. These results show that slag coated with biofilm is distinctively different from an original slag coated without biofilm in terms of buffer action. This processing technique using microbes could contribute to the development of a novel application of slag as a recycled material.