• Xabier Vázquez Campos added an answer:
    Can buffers be added to LB media to resist change in pH? or can anyone please suggest any method to maintain the pH of media in acidic range?

    the pH of media increases on bacterial growth. I have to maintain the pH of media in acidic range. Is there any way to achieve it? Will the chemical added for pH maintenance affect the growth of bacteria and whether that media can be autoclaved or not?

    Xabier Vázquez Campos · University of New South Wales

    What pH are you talking about?

    Any acidification in a complex medium will cause hydrolysis of some of the components, especially at high temperatures. All depends if that is a problem for you or not. Some manufacturers indicate that the pH of some media can be lowered with lactic or tartaric acid. Quite common in some fungal media

    There are several buffers at low pH, e.g. citrate, phosphate,..., but keep in mind the osmolarity of the medium. It can have a detrimental effect on some bugs.

    Also, if you are preparing solid media, the agar will hydrolyse too, at least partially. For this you can autoclave separately the media and the agar and mix them together when they cool down.

  • Pavel Pazdera added an answer:
    Could someone provide the methods for metal recovery of spent catalyst for treatment of industrial waste to use it as catalyst?


    1- chlorination

    2- acid leaching

    3- alkali leaching

    4- bioleaching

    5- roasting with soda salt

    Pavel Pazdera · Masaryk University

    O. K., it is now clearer. See references in

  • Cansu Demirel added an answer:
    Is bioleaching method applicable to industrial-scale copper sulfide (Cu-Fe-S)?

    I am very interested in the field of hydrometallurgy and decided developed a manufacturing plant copper by hydrometallurgy method. However, due to the use of sulfide ores (Cu-Fe-S) we are forced use of bioleaching technology. Does the subject written in the articles for procedures for hydrometallurgy, is this done on an industrial scale?

    Cansu Demirel · Istanbul Technical University

    What Marco mentioned is true. Apart from jarosite precipitation which is a major problem in bioleaching, chalcopyrite has a refractory nature to hydrometallurgical processes. Optimization of  chalcopyrite bioleaching applications are still in progress via adjusting Eh, temperature and pH or using several catalysts like silver and chloride (Watling, 2006; Li et al., 2013; Bevilaqua et al., 2013; Feng et al., 2013). 

    I am adding the reviews and  research papers I cited here:

    Li et al. (2013)

    Watling (2006)

    Bevilaqua et al. (2013)

    Feng et al. (2013)

  • Freddy Dardenne added an answer:
    What is the meaning of "Neutral pH bioleaching of heavy metals"?

    Is it

    a. Micro-organisms used for leaching are neutrophiles.

    b. The leaching (metal solubalization) happens at neutral pH.

    c. Both a and b

    d. Neutrophiles produce lixiviant (which is at lower pH). This lixiviant is further used for leaching.

    also kindly mention advantages of "Neutral pH bioleaching" over "acidophilic bioleaching".

    Freddy Dardenne · University of Antwerp

    If your question is about resolubilizing metals from sediment into the water column in an ecotoxicological context; the answer is much more complicated. The underlying driver is in that case not pH, but O2 concentration. 2 references that might give some insight:

    De Jonge M, Teuchies J, Meire P, Blust R & Bervoets L (2012) The impact of increased oxygen conditions on metal-contaminated sediments part I: Effects on redox status, sediment geochemistry and metal bioavailability. Water Research 46: 2205-2214.
    De Jonge M, Teuchies J, Meire P, Blust R & Bervoets L (2012) The impact of increased oxygen conditions on metal-contaminated sediments part II: Effects on metal accumulation and toxicity in aquatic invertebrates. Water Research 46: 3387-3397

  • Luis A. Salcedo Mejía added an answer:
    Is the bacterial leaching a (non-polluting) ecofriendly technology? If so why?

    I have reviewed several papers in which this phrase is mentioned but not described why it is.

    Luis A. Salcedo Mejía · Universidad Nacional Federico Villareal

    Thank you very much for yours answers.
    but I need have papers . 

    thank you

  • Lawrence Margulies added an answer:
    How can I prepare bioleaching residue samples for XRD analysis?

    After bioleaching of pyrite or chalcopyrite, orange-brown residues are precipitating. How can I prepare them for XRD analysis to understand the components?

    Lawrence Margulies · University of Guelph

    mortor and pestle and elbow grease. Oh, and Ian is right, that Fe fluorescence can be a headache when using Cu-Kalpha radiation if you don't have an energy sensitive detector with a discriminator with high enough energy resolution.

  • Lala Behari Sukla added an answer:
    What are the new challenges in the use of sea water in bioprocess industries?
    We may face shortage of water in bioprocess industries. Sea water may be the real alternative.The high costs associated with transportation and desalination may be the real issue.
    Lala Behari Sukla · Council of Scientific and Industrial Research (CSIR), New Delhi

    “Marine debris like plastic, glass, metal, rubber abandoned fishing nets and other gear often get entangle and kill reef organisms and break or damage them,” said Dr. Mahua Saha, senior Scientist from National Institute of Oceanography (NIO) addressing representatives of SAARC nations during a workshop held at Port Blair, Andaman.

  • A.U. Daniels added an answer:
    Is it possible the metabolism of bacteria change by the time?


    I am studying about the effect of bacteria and their metabolic byproducts on the metal surfaces. In my project, I found one kind of bacteria with a high corrosion inhibitory effect on steel alloys. FESEM images observed that an inhibiting layer covered the surface after 6 h. This layer strengthened by exposure time; so after several days the inhibitory effect reached to its highest value and became stable. We found these results in summer and we continued our work until now. Unfortunately, in last two months, we couldn’t get the same results from bacteria (even in same situation). I was thinking maybe bacteria has problem, so I took bacteria from the Bank again and studied. But the bacteria don’t have inhibitory effect anymore. According to FESEM results, we found that bacteria attached to surface, but the inhibitive layer didn’t form on the surface. So I really confused whether the property of bacteria can be change by the time? It seems bacteria didn’t produce EPS or biofilm on the surface, anymore. So, is it possible the metabolism of bacteria changed by the time?

    A.U. Daniels · Universität Basel

    As others said, bacterial metabolism can change with time. However, it seems to me that you are really asking another question: why did the bacteria no longer form a biofilm? 

    You say that you used "the same situation". Are you really sure of that? Perhaps the metal surfaces you used when the bacteria failed to form a biofilm are not really the same as those you used when they did form a biofilm. Have you checked in some way that your metal surfaces are the same? -- same cleanliness, same oxide film (passivation), same wettability, etc. 

  • Luis A. Salcedo Mejía added an answer:
    Is it effective to determine iron II with potassium dichromate in the presence Iron III?

    I realize experiments of bioleaching of polymetallic ores with bioleaching consortia, and want to determine iron (II). 

    My protocol is:

    To 1mL sample (aprox pH 2- 5) add 1mL solution H3PO4:H2SO4 (1:1), homogenize.

    Add 23 mL H2O, homogenize.

    Add 0.1 mL of diphenylamine sulfonate (0.3%).

    Titritation with potassium dichromate (0.5mM)

    Luis A. Salcedo Mejía · Universidad Nacional Federico Villareal

    Thanks you for all us.

  • Natasa Adamou added an answer:
    What cryoprotective agents should I use for bioleaching bacteria?

    Acidithiobacillus ferooxidans, Sulfobacillus acidophilus, Sulfobacillus Thermosulfidooxidans, Sulfolobus acidocaldarius.

    Natasa Adamou · Cyprus University of Technology

    Thank you very much for your help mr.Brandl.

  • Luis A. Salcedo Mejía added an answer:
    When using heap leach or stirred tank bioreactors, does it depend on the mineral to use?
    There are many processes / patents using bioleaching of sulphide ores or oxidized copper / gold, using both batteries as bioreactors, but this will depend on that? The percentage of precious metal law?
    Luis A. Salcedo Mejía · Universidad Nacional Federico Villareal

    thank yous for all.
    very much thanks you

  • Luis A. Salcedo Mejía added an answer:
    Why can't Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans grow successfully in inorganic solid medium (as 9K, TK, etc.)?
    In liquid cultures with inorganic ferrous sulfate At. ferrooxidans and L. ferrooxidans grow fine but when trying to isolate on solid medium which is growing successfully At. ferrooxidans and L. ferrooxidans show no reproducible sporadic growth.
    Luis A. Salcedo Mejía · Universidad Nacional Federico Villareal
    thank you very much Xavier.
    And could consider a response to genomic level, differences between the genomes of these two species can suggest changes in microbiological assays.
    L. ferrooxidans suggests as being the predominant organism on At. ferrooxidans bioleaching processes.

    best regards
  • Fereydoun Hosseinzadeh added an answer:
    Can we enrich uranium through a process of bioleaching? How?
    Methods and any other ideas are welcome.
    Fereydoun Hosseinzadeh · National Institute of Genetic Engineering and Biotechnology
    Mr Sebtain Afzal
    Thanks alot for this articles
  • Lala Behari Sukla added an answer:
    Is it possible to suggest new approaches for evaluating wastes?
    The waste problem has increased considerably with rapidly increasing population and improvement at industry by developing technology. It is necessary to evaluate the wastes by recovering metals(valuable) from these wastes. Main target of waste management is to detoxify these materials for environmentally safe deposition.
    Lala Behari Sukla · Council of Scientific and Industrial Research (CSIR), New Delhi
    Plasma gasification has become a buzzword and the new kid on the waste to energy block. One company has trialled its new process in Mexico, known as microwave plasma gasification, and is starting work on its first commercial facility in Texas. Tom Freyberg investigates claims that the process is 60% more efficient and can produce diesel from waste
  • Mihail Iliev added an answer:
    Are there promising prospects for recovering heavy metals using microbes?
    Bioleaching to recover metal from waste is simpler, and therefore cheaper to operate and maintain. Fewer specialists are required to operate a complex chemical plant/factory.
    Mihail Iliev · Sofia University "St. Kliment Ohridski"
    Check one of the top scientist in this field - Groudev, S.N.
  • Lala Behari Sukla added an answer:
    Can anyone give me an idea regarding pressure oxidation of chalcopyrite?
    A chalcopyrite based ore if autoclaved in MSM media at neutral pH, can it be oxidized? if yes then to what extent?
    Lala Behari Sukla · Council of Scientific and Industrial Research (CSIR), New Delhi
    The smaller the ore granularity, the higher the chalcopyrite leaching rate, so the ores are milled fully before the experiment..Firstly, O2 diffuses into water from the gas/liquid
    interface and then diffuses furthermore. It participates in reaction after it touches the ore surface. It is known that the influence of O2 on the chemical reaction is dependent
    on each O2 diffusible step during the above process. The gas solubility in the water is affected by the temperature and p(O2). The pressure of O2 has direct proportion to the
    O2 concentration in the water. Enhancing p(O2) promotes the O2 solubility and the oxidation speed is increased
  • Iveta Styriaková added an answer:
    In bioleaching application (the releasing of metals from raw material) will fungi or heterotrophic bacteria have better utilization?
    I think fungi produce many allergens and mycotoxins. That is why I have an interest in heterotrophic bacteria.
    Iveta Styriaková · Slovak Academy of Sciences
    Dear Debabrata, it is important fact which I will consider during laboratory experiment. Dear Lala, I often use Bacillus in my bioleaching experiments and I am very satisfied with bacterial activities in the bioleaching of black shale.
  • Lala Behari Sukla added an answer:
    Can anyone suggest current and future trends in using modified microorganisms?
    This is an enormous topic and one of great complexity. Genetic modification means artificially changing the genetic material of an organism. The term genetic modification and genetic engineering are interchangeable. Genes can be moved between species, and between different levels of biological microorganism.
    Lala Behari Sukla · Council of Scientific and Industrial Research (CSIR), New Delhi
    When microorganisms are isolated from nature, their performance in producing desired products is rather poor. Metabolic engineering is performed to improve the metabolic and cellular characteristics to achieve enhanced production of desired product at high yield and productivity. Since the performance of microbial cell factory is very important in lowering the overall production cost of the bioprocess, many different strategies and tools have been developed for the metabolic engineering of microorganisms.
  • Lala Behari Sukla added an answer:
    What are the challenges in developing microbial process for recovering metals from oxidic ores?
    Treating oxidic ores through bioleaching process is a great challenge for microbiologists and engineers.
    Lala Behari Sukla · Council of Scientific and Industrial Research (CSIR), New Delhi
    Bioleaching is a profitable alternative to the conventional chemical process of uranium recovery. The leaching of U from low-grade ores and solid wastes is realized by chemoautotrophic bacteria such as Acidithibacillus ferrooxidans. Uranium reducing bacteria, particularly Shewanella putrefaciens and Shewanella oneidensis, can be used for UO2 particles synthesis. The bioreduction of U(VI) in the presence of hematite particles can be a way to new catalyst fabrication. (Physicochem. Probl. Miner. Process. 49(1), 2013, 71−79 )
  • Sandeep Panda added an answer:
    Why do we often face problematic issues in scaling up of microbial cultures?
    When we culture microorganisms in lab scale we get results with efficiency. However, when such microbial cultures are aimed for scaling up for an industrial application (may be in diverse fields) we face a lot problems. How can these issues be resolved? What care should be taken?
    Sandeep Panda · Institute of Minerals and Materials Technology
    I have worked in an industrial heap bioleaching operation. Now interestingly, as everyone has discussed, it is indeed a great problem when we scale up. As in my case where bacterial solution is prepared at once in some cubic meters in open bioreactors under natural environmental conditions, the volume is affected by evaporation losses which has to be daily monitored and compensated with appropriate water or media. Also homogenity is a issue. Still we have tried to minimize the problems and are still working on to provide an easy and faster way to recover metal values using microbial biotechnology.
  • Lala Behari Sukla added an answer:
    Can bioinformatic predictions play an important role in application of bioleaching process on an industrial scale?
    Bioinformatics information towards bioleaching.
    Lala Behari Sukla · Council of Scientific and Industrial Research (CSIR), New Delhi
    With about 300 fully sequenced bacterial and archaeal genomes and with additional information of hundreds of thousands of DNA and protein sequences in public databases it is possible to predict genes and their putative protein products in DNA sequences derived from genome sequencing projects. In this chapter, it provides a general overview of how bioinformatics and genome biology can provide insight into the genomic organization and function of biomining microorganisms with a special reference to Acidithiobacillus ferrooxidans about which most is known. Bioinformatics and genome biology are effective tools for making preliminary inroads into how an otherwise uncharacterized organism functions. It is particularly powerful in cases where it is difficult to implement conventional genetic tools such as in the case of several bioleaching microorganisms and results are beginning to emerge to support this view
    The Use of Bioinformatics and Genome Biology to Advance Our Understanding of Bioleaching Microorganisms
    Chapter in book “Microbial processing of metal sulphides”, eds. W. Sand and E. Donati. Springer (accepted).
  • Lala Behari Sukla added an answer:
    Can anyone give a possible idea related to the use of iron reducing bacteria (IRB) for chalcopyrite processing or leaching
    Lala Behari Sukla · Council of Scientific and Industrial Research (CSIR), New Delhi
    The number of biotechnological applications of IRB, including remediation of soils and sediments contaminated with metals, radionuclides and organics, is rapidly increasing.Bioleaching of iron from kaolin using Fe(III) reducing bacteria has been studied.Nickel present in goethite has been released using IRB in case lateritic ore. A lot of progress has been made towards understanding of the phylogeny, ecology and biogeochemical role of dissimilatory iron-reducing bacteria. The known phylogenetic range of iron-reducing bacteria has expanded considerably, as has the known range of iron minerals that serve as a source of Fe(III) for anaerobic respiration. You can try IRB for processing of Chalcopyrite.I think IRB may break the Chalcopyrite structure and help in releasing copper into solution.

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