Biosorption of a dye and heavy metals using dead cells of filamentous bacterium, Aureispira sp. CCB-QB1
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ORIGINAL PAPER
Biosorption of a dye and heavy metals using dead cells of filamentous bacterium, Aureispira sp. CCB‑QB1 N. A. R. Hasyimah1 · G. Furusawa1 · A. A. Amirul1,2 Received: 9 May 2020 / Revised: 6 August 2020 / Accepted: 1 September 2020 © Islamic Azad University (IAU) 2020
Abstract Biosorbents are useful for removing pollutants, such as synthetic dyes and heavy metals, from aqueous solutions. Our previous report demonstrated that Aureispira sp. CCB-QB1, which is known as a bacterial predator, exhibited cell aggregation and adsorbed its bacterial prey in the presence of calcium ion, suggesting that the QB1 cells are able to adsorb the pollutants and have potential for a novel biosorbent. Thus, in this study, the adsorption activity of QB1 dead cells on a dye and heavy metals was tested. The dead cells were produced by treating the cells with 0.5% formaldehyde. The dead cells exhibited robust adsorption activity on kaolin similar to that of the living cells. 88.1% of a diazo dye, Congo red (initial conc. 0.2%), were removed from the solutions in the presence of 50 mM C aCl2. About 90% of F e3+ and C u2+ ( F” less than 0.05 indicated that the model terms were significant. In this case, A, B, C, AC, BC, A 2, B2 2 and C were significant model terms. The lack-of-fit F-value which was 4.77 showed that the lack-of-fit was not significant relative to the pure error. The “Adj R-Squared” obtained for cell growth was 0.9042. This value indicated that the experiments were conducted with high precision and reliability. Table S3 shows the ANOVA and regression for the QB1 absorption activity. From table, the F-value of 37.48%
International Journal of Environmental Science and Technology
implied that the model was significant with the value. From the results, the model terms of B, C, BC, B 2 and C 2 were significant. In addition, the lack-of-fit was not significant relative to the pure error with F-value of 4.79. Overall, the “Pred R-Squared” of 0.8112 is in reasonable agreement with the “Adj R-Squared” of 0.9453, which explained the reliability and precision of the experiment carried out. Figures 6 and 7 show the 3D response surface plots that represent the interaction effects between two factors for each response studied. Based on Fig. 6a, it can be demonstrated that the cell growth increased along with the concentration of sea salt from 2 to 4%. The 16S rRNA gene sequence of the Aureispira sp. CCB-QB1 showed 99.6% similarity to Aureispira maritima strain (Furusawa et al. 2015b). A. maritima was a slightly halophilic bacterium, thus it required not much amount of sea salt to stay alive and to support the cell growth (Saelao et al. 2011). This result indicated that Aureispira sp. CCB-QB1 also prefer slightly halophilic condition as well as A. maritima. The cell growth also increased gradually from 16 to 32 h of incubation period. Figure 6b shows that the cell growth increased from 0.50 to 1.125% of peptone concentration but decreased when the concentration of peptone was increased further. Only a nar
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