Studies On Culture Condition And Characterization Of Bioleaching Of Ferroplasma Spp.

Ferroplasma spp. plays an important role in bioleaching systems, while the bioleaching mechanism of the genus has not been discussed clearly.This work focused on the detection of bioleaching abilities and mechanism of sulfide ores with four representative Ferroplasma strains. Quantitive PCR was employed to investigate the population dynamics of the moderate thermophiles during bioleaching of chalcopyrite and pyrite. The effect of Ferroplasma spp. on elimination inhibitory effect of organic compound on autotrophic microorganism such as L. ferriphilum and Acidithiobacillus caldus was learned through Quantitive PCR in pure cultures and mixed cultures. Experiments listed above aimed to detect the ecological function of Ferroplasma spp. in bioleaching, in order to provide guidance on leaching of sulfide ores by moderate thermophiles.Growth conditions were investigated to make a summary as below: The archea Ferroplasma spp. are acidophilus and thermophilic, with no cell wall and various cell shapes. The optimal growth temperature of Ferroplasma spp. is above 37℃and the optimal growth pH value is between 0.5 with 2.0, Ferroplasma spp. can derive energy from the oxidation of ferrous ion. Ferroplasma spp. are capable of chemomixotrophic growth on ferrous sulphate and 0.02%(w/v) of yeast extract, with rapid absolute oxidation of iron to obtain energy.Ferroplasma spp. mixed with other three bioleaching microorganisms grew separately in batch culture contain chalcopyrite, certain parameters were investigated to detect the bioleaching abilities of Ferroplasma spp.. Ferroplasma spp. has the ability of leaching pyrite and chalcopyrite, but weak when compared with mixed cultures. This validates the view that Ferroplasma spp. can directly provide oxidant for dissolution of chalcopyrite. Moreover, At. caldus s2 and L. ferriphilum YSK were limited by their metabolite, Whereas this inhibition can be removed by Ferroplasma spp.. According to height of leaching abilities of chalcopyrite, Ferroplasma spp. are listed as F. thermophilum L1＞F. acidiphilum Yt>E cupricumulans BH2> E acidarmanus Ferl.The effects of Ferroplasma spp. in pyrite leaching were not so remarkable as in chalcopyrite leaching, with not so many heavy metals ions. E. acidiphilum Yt gave a better performance as a result of its particular growth characteristics. Mixed cultures kept at higher oxidation-reduction potential and lower pH value, facilitating more pyrite oxidation.Quantitive PCR was applied to comparatively study the variation of mixed cultures in leaching of chalcopyrite and pyrite. It showed that At. caldus s2 always occupy an important position in mixed cultures, the Ferroplasma spp. kept a small proportion at the beginning, to the end, took up large scale in the anaphase of the bioleaching and became the primary bacteria for Fe2+oxidation. The proportion of Sulfobacillus sp. LN as well as L. ferriphilum YSK was declined as the time went on.The growth and Fe2+oxidation activity of L. ferriphilum YSK were totally inhibited with 0.04%(w/v) yeast extract. The results indicated that F. thermophilum L1 can efficiently eliminate the inhibition of yeast extract to L. ferriphilum YSK, consequently, Ferroplasma spp. can accelerate metal sulfide dissolution for L. ferriphilum YSK. Quantitive PCR also confirmed this deduction by final portion of 29.6%. The other combination At. caldus s2/E thermophilum L1 showed that F. thermophilum L1 had no effect on the growth of At. caldus s2 with an addition of 0.04%(w/v) yeast extract. Relevant quantitative PCR gave similar results, growth of F. thermophilum could be detected with no yeast extract added in the mixed cultures as At. caldus s2 may be the supplier of organics needed for the growth of F. thermophilum.