1 The importance of biometallurgical strain breeding
Biometallurgy is a technology that uses minerals as an energy source to oxidize and decompose minerals to make metal ions into human solution (bioleaching). After further separation and extraction of metals, it has the characteristics of short process, low cost, environmental friendliness and low pollution. It is especially suitable for handling low grade mineral resources. However, due to the lack of excellent strains and flora, the bioleaching rate is slow and the leaching rate is low. Therefore, screening for good strains and reasonable population combinations is extremely important for improving the efficiency of biometallurgical leaching.
2 Metallurgical microbial diversity
As microbes continue to oxidize sulfide ore, their environmental conditions, such as pH, temperature, and concentration of soluble metal ions in the solution, are constantly changing. These special environmental conditions necessarily limit the diversity of life forms. The life forms present in bioleaching tanks, immersion reactors or bioreactors are generally simple, often belonging to single-celled organisms, and their dominant flora is mainly bacteria and archaea, most of which live at pH 1-4. In an acidic environment. At present, relating to the bioleaching microorganisms are those capable of oxidizing the ferrous ion, or (and) species closely related redox inorganic sulfur, including Thiobacillus acidophilus (of Acidithiobacillus), the genus Leptospira (of Leptospirillum) , Sulfolobus, Sulfobacillus, Acidia-nus, Acidiphiliun, me tallosphaera, and Ferroplasma, A total of 8 genera.
Moderate thermophilic leaching bacteria
Moderate thermophilic leaching bacteria mainly include the following:
(1) Acidithiobacillus. The genus includes four types of eosinophilic ferrous oxide thiobacillus acidophilus, sulfurous acid thiobacillus, thiobacillus acidophilus and Acidithiobacillus ferrivorans. Among them, Acidithiobacillus caldus is the only moderately thermophilic leaching strain in this genus. The optimum growth temperature is generally 40-55 °C, most of which is around 45 °C, and a few strains can be as low as 35 °C. . The strain was isolated, identified and named in 1994 by Hallberg and Lindstrom [4]. Heterophilus acidophilus is aerobic, capable of oxidizing elemental sulfur and reduced inorganic sulfide. It has many physiological and biochemical types. In the presence of yeast extract, the growth rate and the activity of the elemental sulfur are greatly increased. Increasingly, most strains can grow rapidly in medium supplemented with glucose and energy material S0. The strain is a major strain in the bioleaching reactor and microbial heap leaching of 40-50 °C, and plays an important role in the moderate thermophilic leaching process of metal sulfide ore. Acidithiobacillus ferrivorans has recently been identified, and its 16S rRNA is highly similar to other species, but genomic DNA and ferrous oxide acidophilus are only 37%, and some key enzymes with ferrous oxidation are also associated with ferrous oxide. Thiobacillus acidophilus is significantly different.
(2) Sultropha genus (Sulfobacillus).
Currently, the genus includes Sulfobacillus thermosulfidooxidans, Sb. acidophilus, Sb. sibiricts, Sb. thermotolerans, and Sulfobacillus benefacien. According to the optimal growth temperature, the genus can be divided into two groups. The first group is a typical moderate thermophilic bacteria, including thermophilic sulfur-oxidized bacterium (50-55 ° C), Siberian sulphate (55-60 ° C), S. acidophilus (45 ~ 50 ° C); the second group is the de facto mesophilic bacteria, only one kind of heat-resistant bacterium, its growth temperature is 38 ~ 42 ° C, in the range of medium temperature [10]. In addition, the first group of thermophilic sulfur-oxidized sulphide and acidophilic sulphate can reduce iron hydroxide, jarosite, goethite, etc. in the presence of anaerobic and organic carbon sources or tetrathionates. Fe3+ in minerals to get the energy needed for growth.
(3) Ferroplasma. The genus is an archaea whose scientific name is derived from the fact that its members lack the typical morphological characteristics of the cell wall and the physiological and biochemical characteristics of ferrous oxide. There are currently three species, Ferroplasmaacidiphilum, F. acidarmanus and F. cupricumulans. Ferroplasma cuqricumulans is a new species of the leaching solution separated recently a low-grade copper Ivanhoe Limited from Burma industry chalcopyrite in heap bioleaching field, growth temperature 22 ~ 63 ℃, optimum growth temperature of 53.6 deg.] C; optimum growth The pH value is 1.0-1.2, and its growth can be seen at a pH of 0.4. It has strong ferrous iron oxidation ability and cannot oxidize sulfur. It is the first moderately thermophilic hi found in the genus Trichophyton. Acidic bacteria.
2. Thermophilic leaching bacteria and extreme thermophilic leaching bacteria
The thermophilic leaching bacteria with an optimum growth temperature of 60-80 ° C and the extreme thermophilic leaching bacteria with an optimum growth temperature exceeding 80 ° C are cross-distributed in the genus Acidianus, me tallosphaera and sulfur leaves. Sulfolobus. These three genera belong to the archaea, and their members are Gram-negative, irregular spheroidal archaea, mostly distributed above 70 °C, high-temperature acid hot spring or boiling spring rich in sulfur and iron.
(1) Acidianus. A typical thermophilic archaea, the growth temperature of various archaea of ​​the genus is 50-95 ° C, the optimum growth temperature is 60-90 ° C; the growth pH is 1.0-6.0, and the optimal growth pH is 1.2- 2.5. There are currently 6 species officially published in alphabetical order, which are A.ambivalens, A.brierleyi, A.infernus, A.manzaensis, A.sulfidivorans and A.tengchongensis. Among them, A.ambivalens, A. infernus and A.tengchongensis are elemental sulfur and reduced sulfide oxidizing bacteria, and the other three species can oxidize sulfur and ferrous oxide. Except for A. infernus, the optimum growth temperature is 90 °C, which belongs to extreme thermophilic bacteria. The optimum growth temperature of the other five species is 65-80 °C, which belongs to thermophilic bacteria.
(2) Sulfolobus. The genus includes 6 species of Sulfolobus me tallicus, S. yangmingensis, S. tokodaii, S. solfataricus, S. shibatae and S. acidocaldarius. Sulfolobus is also an archaea. Growth pH is 1.0 to 5.0,
A suitable pH is from 1.5 to 3.0. The genus archaea is mostly thermophilic bacteria of 60-80 ° C, and a few are extreme thermophilic bacteria above 80 ° C, such as the extreme thermophilic strain JP3 of S. solfataricus.
(3) Metalosphaera. The genus Metalococcus was established by Huber et al. in 1989 according to the model metalospha-erasedula, which is also an archaea. There are three species so far, namely me tallosphaerasedula, M.prunae and M. hakonensis. The bacterium is aerobic, but grows best under mixed nutrient conditions where inorganic energy and yeast extract coexist. In sulphide ores, such as pyrite, sphalerite, chalcopyrite, and elemental sulfur autotrophic growth, proved 0.01% ~ 0.02% (w / v) yeast extract can promote the leaching effect. M.prunae and M.sedula have been successfully used for the biooxidation and bioleaching of sulfide ore. M.sedula has been proven to be one of the more efficient leaching strains.
3 Separation of metallurgical microorganisms
As can be seen from Table 5-1, there are many methods for separating bacteria from plates, but it has been proved that the successful method of laboratory culture is better than the development of double-layer plate technology. The basic principle is to use a kind of saccharide released by the hydrolysis of the Acidiphilium SJH absorption coagulant called acidophilic heterotrophic bacteria and the metabolic waste generated by bacterial growth, thereby eliminating the external environment that affects the growth of the specialized chemical inorganic bacteria. Factors that make it grow better. Of course, even a well-recognized, ideal culture method is not omnipotent. Because everyone knows that at present, less than 1% of the microorganisms can be isolated and cultured on the earth. Fortunately, with the development of molecular biology, especially the rapid development of genomics and metagenomic sequencing technology, it is expected to make significant progress in the separation of microorganisms that are difficult to cultivate. Recently, a new species of Leptospirillum Ferrodiazotrophum, a new species of Leptospira, isolated by a selective separation strategy using random sequencing data (from an acidic pit water environment) is a clear example.
Isuzu Turbocharger Core,Isuzu Turbocharger Cartridge,Isuzu Rhf4 Chra,Isuzu Rhf4 Core Assembly
Fengcheng Fire Turbocharger Manufacturing Co; Ltd. , https://www.fireturboexpert.com