Microbial Population of Industrial Biooxidation Reactors

Abstract

Microbial population performing biooxidation of flotation concentrate of gold bearing sulfide ore containing pyrite, arsenopyrite, and pyrrhotite was studied using cultural and molecular biological (metagenomics sequencing of V3-V4 fragments of 16S rRNA gene) approaches. The biooxidation of the concentrate was conducted at temperatures from 38 to 42°C. Strains of Acidithiobacillus thiooxidans, Acidiphilium multivorum, Leptospirillum ferriphilum, Sulfobacillus thermotolerans, Ferroplasma acidarmanus, and Ferroplasma acidiphilum were isolated from the samples of the pulp from biooxidation reactors. It was shown that optimum temperatures of isolated strains were from 38 to 40°C. Metagenomic analysis demonstrated predominance of the genera Acidiferrobacter, Acidithiobacillus, Acidiphilum, Leptospirillum, and Ferroplasma. According to results of molecular biological analysis, share of the genus Acidithiobacillus was of 0 to 25%, share of the genus Acidiferrobacter was of 7 to 56%, share of the genus Acidiphilum was of 0.03 to 36%, share of the genus Leptospirillum was of 0.7 to 7%, whereas share of the archaea of the genus Ferroplasma was of 33 to 94%. Thus, it was shown that representatives of the genus Ferroplasma can play significant role in bioleach process. Representatives of the genus Acidiferrobacter were previously detected in acid mine drainages, acid soils as well as in bioleach heaps and reactors, whereas data on predominance of the genus in tank bioleach processes have not been presented in the literature. In the present study, strains of the genus Acidiferrobacter were not isolated despite application of the nutrient media recommended for Acidiferrobacter and their properties were not studied. Nevertheless, results of the present study suggest that representatives of the genus Acidiferrobacter have a great impact on industrial bioleach processes.