Optimization Of Culture Condition Of Ferroplasma Thermophilum L1 And Characterization Of Bioleaching

The genus Ferroplasma plays an important role in bioleahcing systems and has a bright future for application. At present, it is difficult to obtain their high cell density cultures, thus it is essential to adjust and optimize the culture condition in shaking flask in order to provide information for scale-up of archeon culture as well as its industrial application. So far, the bioleaching characterization of Ferroplasma spp. has not been quantified, especially for its elimination inhibitory effect of organic compound on autotophic microorganism especially L. ferriphilum. The primary result are as follows:(1) By investigating the cell density and the Fe²⁺ oxidation velocity, The results showed that the optimum culture conditions of F. thermophilum L1 are as follows: 50℃, initial pH 0.5, 50 mL working volume in 250 mL shaking-flask, inorganic nitrogen source (NH₄)₂SO₄. The optimum combination of FeSO₄·7H₂O, yeast extract and peptone was determined by orthogonal experiments, including FeSO₄·7H₂O 40 g/L, yeast extract 0.3 g/L, peptone 0.2 g/L. Under the optimum culture conditions, the cell density was up to 6.3×10⁷ cell/mL, and the oxidation of 40 g/L ferrous sulfate heptahydrate was finished in less than 72 hours.(2) The bioleaching characterization of sulphide ores by F. thermophilum L1 was studied. The results showed that:â‘ F. thermophilum L1 has weak ability of leaching pyrite and chalcopyrite;â‘¡For further study, two bioleaching system, A: At. caldus s2/L. ferriphilum YTW315/F. thermophilum L1 and B: L. ferriphilum YTW315/At. caldus s2 were designed, and the concentration of Cu²⁺, bioleaching rate, concentration of Fe²⁺ as well as bacteria number was comparably studied. System A was more efficient than B in chalcopyrite dissolution, this may owing to Ferroplasma spp. can directly provide oxidant for dissolution of chalcopyrite. Moreover, At. caldus s2 and L. ferriphilum YTW315 were limited by their metabolite, Whereas this inhibition can be removed in the presence of F. thermophilum L1.(3) Real-time PCR was applied to comparatively study the regular pattern of free and attached population dynamics in the system A and B. The results showed:â‘ There was discrepancy of free and attached bacteria in system A. The proportion of free At. caldus s2 as well as L. ferriphilum YTW315 was declined as the time went on. In the first 8 days, free F. thermophilum L1 suddenly decreased, but then keep incresed until up to 32% in the final. The attached At. caldus s2 show little decline, but L. ferriphilum YTW315 constantly increased. The attached F. thermophilum L1 kept small proportion all the way;â‘¡The population dynamics of free bacteria was consistent with attached bacteria in system B. The free and attached At. caldus S2 kept decline, but L. ferriphilum YTW315 was the other way round;â‘¢F. thermophilum L1 did not affect the variable trend of At. caldus S2, but made the proportion of free L. ferriphilum YTW315 decline;â‘£The free F thermophilum L1 took up large scale in the anaphase of the bioleaching and became the primary bacteria for Fe²⁺ oxidation.(4) Experiments showed that F. thermophilum L1 can efficiently eliminate the inhibition of organic to L. ferriphilum YTW315, consequently, the deduction Ferroplasma spp. can accelerate the oxidation of ferrous iron dissolution for L. ferriphilum YTW315 was proved.