Applied Microbiology - Role of microbes in Nitrogen cycle , Biofertilizers, Single cell protein, Production of curd and vinegar & reconversion of wastes

A brief account of the role of microbes in Nitrogen cycle, as biofertilizers, in production of curd and vinegar & reconversion of wastes

1. APPLIED MICROBIOLOGY Dr. Saji Mariam George Associate Professor Assumption College Autonomous Changanacherry .

2. Role of microbes in Nitrogen cycle Biogeochemical cycles – The chemical elements of protoplasm tend to circulate in the biosphere from environment to organisms and back to the environment. Nitrogen cycle Cyclic movement of Nitrogen from environment to organism and back to the environment . One of the gaseous cycles in the ecosystem.

3. NITROGEN CYCLE http://www.biologydiscussion.com/plant-physiology-2/nitrogen-metabolism/nitrogen-cycle-with-diagram-2/22876

4. Nitrogen Essential constituent of proteins, nucleic acids, vitamins, coenzymes, alkaloids etc. Free Nitrogen of the atmosphere (79 % ) – unavailable to plants. Microorganisms play important roles in various processes of Nitrogen cycle such as Nitrogen fixation, Ammonification , Nitrification and Denitrification .

5. Nitrogen fixation Diazotrophs Prokaryotic microorganisms that can fix free Nitrogen of the atmosphere into absorbable form - biological Nitrogen fixation.

6. a ) Free living (non – symbiotic ) Nitrogen fixing microbes Live freely and independently in the soil. Requires no host to carry out Nitrogen fixation. Aerobes E.g . Azotobacter , Azospirillum etc.

7. Free living Nitrogen fixing Aerobes Azotobacter Azospirillum

8. Free living Nitrogen fixing Anaerobes e.g. Clostridium sps . Desulphovibrio sps .

9. b ) S ymbiotic Nitrogen fixing microbes - Rhizobium , Bradyrhizobium , Sinorhizobium etc. Rhizobium is rod shaped, gram negative, motile bacteria. They can grow either free - living in soil or can infect leguminous plants . Rhizobium is host specific- infects and nodulates specific host legumes - Pea, Beans, Soy bean ( Leguminosae ) and establish a symbiotic relationship - both partners are mutually benefitted. Possess Nif gene for Nitrogen fixation - produce enzyme Nitrogenase and red pigment leghaemoglobin which protect the oxygen sensitive Nitrogenase enzyme .

10. Mature root nodule is the site of Nitrogen fixation. The atmospheric Nitrogen is reduced to Ammonia and is released into the host plant cells where it is assimilated into various organic nitrogen compounds. Bacteria receive nutrients from the plant and the plant in turn get nitrogenous compounds.

11. Symbiotic Nitrogen fixation by Cyanobacteria E.g. Nostoc , Anabaena etc. fix atmospheric Nitrogen by heterocysts . Anabaena azollae establish symbiotic relationship with the water fern, Azolla which is widely used to enrich paddy fields with fixed Nitrogen. Anabaena – Azolla Symbiosis Image :http://theazollafoundation.org/azolla/the-azolla-anabaena-symbiosis-2/

12. Fixed Nitrogen is absorbed by plants – incorporated into proteins and other organic Nitrogen compounds Animals depend plants either directly or indirectly for their food – synthesize animal proteins and other Nitrogen containing biomolecules .

13. 2. Ammonification The dead organic matter of plants and animals are degraded by ammonifying bacteria ( Bacillus , Clostridium , Proteus , Pseudomonas ) and form Ammonia. 3. Nitrification Nitrifying bacteria oxidize Ammonia into nitrates. First, Ammonia is oxidized to nitrite by bacteria such as Nitrosomonas , Nitrosococcu s etc. Nitrite is further oxidised to nitrate by the bacteria Nitrobacter . Plants absorb Nitrogen mostly in the form of nitrates. 4. Denitrification Some bacteria such as Pseudomonas denitrificans , Thiobacillus denitrificans etc. reduce the nitrates of the soil to gaseous Nitrogen. This results in the reduction of fertility of the soil.

14. BIOFERTILIZERS Cultures of improved strains of nitrogen fixing and phosphate solubilizing bacteria are used as biofertilizers . Stimulate plant growth by increasing the availability of nutrients.

15. TYPES OF BIOFERTILIZERS Nitrogen fixers Symbiotic nitrogen fixers Examples: Bacteria Rhizobium leguminosarum – for Pea- Pigeonpea , Green gram, Black gram, Cowpea; Groundnut, Soybean. R. phaseoli - for Beans   R. japonicum - Soy bean Cyanobacteria (Blue green algae) Anabaena – Azolla symbionts - for upland and low land Paddy.

16. Free - living (non –symbiotic ) nitrogen fixing bacteria Examples: Azotobacter (for Wheat, Maize, Cotton, Potato, Mustard, Sugar cane) Azospirillum ( Wheat , Corn, Paddy, Sugarcane, Sorghum ) . Actinomycetes Frankia - can be used for reclamation of degraded lands.

17. 2. Phosphorous Suppling Biofertilizers (PSB) Phosphorous solubilizers or Phosphobacteria - Solubilize different forms of insoluble phosphates by producing citric acid, succinic acid, fumaric acid etc. e.g. Bacillus polymyxa B. megatherium var. phosphaticum Pseudomonas striata

18. 3. Phosphorous mobilizers or Absorbers Vesicular Arbuscular Mycorrhizae (VAM) fungi ( Mycorrhiza – Association of fungi with the root system of higher plants) VAM fungi colonize the root and increase the growth of plants. Increase the uptake of Phosphorous which move slowly in soil solution. Production of growth promoting substances Can increase yield to 30 -40% Better water holding capacity and tolerance of drought

19. 4. Trichoderma as biofertilizer Selected strains of Trichoderma are used as biofertilizers - Trichoderma harzianum is a good solubilizer of Phosphorous. Enhances the uptake of water and nutrients , especially Nitrogen, which leads to higher nutrient metabolism – increases yield. Increases root and shoot growth. The plant also develops greater resistance to diseases , drought and salt. Reduces the activity of deleterious microorganisms in the rhizosphere of plants. Colonize on the roots of the host plant, attack and kill the soil pathogens – hence also used as a biocontrol agent.

20. Trichoderma as Biofertilizer … Image: https://www.indiamart.com/proddetail/trichoderma-biofertilizer-6706620633.html

21. Methods of Application of Biofertilizers Seed treatment or Seed inoculation - Biofertilizers like Azotobacter , Azospirillum , Rhizobium etc. are used for seed treatment. Dipping of seedlings – The seedlings are dipped in the solution of biofertilizers before transplanting. The treated seedlings are then transplanted in the field . E.g. Azospirillum is used for dipping of paddy seed lings. 3. Soil Application – The biofertilizers are mixed with well dried, powdered Farm yard manure (F.Y.M.). or compost and applied to the field just before sowing of seed or transplanting of seed lings.

22. Advantages of Biofertilizers Improve cycling of nutrients and increase soil fertility . Increase porosity and water holding capacity of the soil and provide protection against drought. Enhance seed germination Increase crop yield to 20 – 30 % Cheap, convenient and ecofriendly Application of biofertilizers have considerable importance in sustainable agriculture.

23. SINGLE CELL PROTEIN Protein derived from a culture of single-celled organisms, used especially as a food supplement. E.g. Cyanobacteria Spirulina  ( Spirulina maxima , Spirulina platensis ) and green alga Chlorella . Include microorganisms that are directly used as food source or as a supplement . Earlier, it was known as ‘Microbial Protein’. The term Single Cell Protein was coined by Scrimshaw (1967) SCP has high protein content, fats, carbohydrates, vitamins, minerals etc. – the composition depends on the organism and the substrate on which it grows. SCP can be used as a human food or cattle feed. Yeast, certain species of algae , fungi and bacteria can be grown on suitable substrates and the cells are harvested as source of protein.

24. Yeasts as SCP Widely used. Large scale production of yeasts is referred to as microbial farming . The edible yeasts are known as food yeasts- contain vitamins like Thiamine (B1), Riboflavin (B2), Nicotinic acid (B3), Biotin ( Vitamin H, a member of B –complex vitamins) etc. E.g. Saccharomyces cerevisiae (Baker’s Yeast), Candida utilis ( Torula yeast), C. guillerimondii , C. tropicalis , C. lipolytica , Torulopsis candida , T. utilis , Debaromyces etc.

25. Saccharomyces cerevisiae (Baker’s Yeast), Candida utilis ( Torula yeast ) widely used for flavoring in  processed  foods and pet foods Image :https://alchetron.com/Torula#-

26. Candida guillerimondii C. tropicalis Image: https://www.semanticscholar.org/ Image: https://www.researchgate.net /

27. Candida lipolytica Debaromyces Image: http://www.bcrc.firdi.org. Image : https://wineserver.ucdavis.edu/

28. Moulds as SCP Trichoderma reesei   Fusarium venenatum   has high protein content -One of its strains is used commercially for the production of SCP - mycoprotein Quorn . Rhizopus oligosporus  

29. Cyanobacteria as SCP Spirulina Spirulina maxima, Spirulina platensis etc. A most popular microbial food supplement. High protein content. Low calorie content. Used as a food source either as dried cake, powdered product, tablets or capsules. Used as a ‘Slimming food’.

30. Algae as SCP Chlorella Unicellular green alga. Contain high amount of protein. Used as a source of food in Japan.

31. Bacteria as SCP Methylophilus methylotrophus Pruteen , produced from bacteria, Methylophilus methylotrophus , cultured on Methanol had 72% protein content, was the first commercial SCP used as animal feed supplement. The bacteria Cellulomonas ,   Alcaligenes are also used for the production of single cell protein.

32. PRODUCTION OF SINGLE CELL PROTEIN STEPS Selection of suitable strain of microorganisms Selection of substrate iii) Culture/ Fermentation iv) Harvesting v) Post harvest treatment. vi) Processing for use as SCP.

33. Selection of suitable strain of microorganisms The quality of protein depends on the type of microbial strain selected. Strains of microorganisms for SCP production should be selected based on their ability to produce protein of high quality capability to grow in ambient conditions ability to use a wide variety of substrates rapid growth rate non- pathogenicity with limited quantity of nucleic acid. Such microbes are isolated from samples of soil, water, air, biological materials etc.

34. ii) Selection of substrate The substrate should be readily utilizable and cheap. Examples: Starch Rice or wheat bran Molasses Ethanol Methanol Fruit pulp Vegetable wastes Lignocellulosic agrowastes Whey from dairy industry Spent sulphite waste liquor derived after wood processing Methane rich natural gas Sewage etc.

35. iii) Culture/ Fermentation The pure culture of the selected strain of microorganism can be cultured in tanks, ponds(e.g. Spirulina ) or in a fermenter or bioreactor- deep lift fermenter , air lift fermenter (e.g. Bacteria) in a suitable substrate under optimum conditions of pH, temperature, aeration etc. The type of fermentation may be submerged (in liquid medium), semi-solid (e.g. Cassava waste) or solid state (e.g. rice or wheat bran) Microbes are cultured in continuous or fed-batch culture.

36. Algal production for SCP Can be cultivated in trenches, ponds etc. Require low intensity of light. Temperature : 35 – 40 °C pH range : 8 .5 – 10 .5 Image: Babul Aktar

37. enfo.agt.bme.hu Algae- biorector for the production of algal SCP

38. Yeast production for SCP can be cultured on molasses,   corn-steep liquor,  starch, pulp of fruits etc. Temperature : 30- 34 °C pH : 3.5 -4.5.

39. iv) Harvesting The bulk of cells can be removed from the fermenter by decantation. v) Post harvest treatment Purification and drying should be simple – centrifugation(yeast, bacteria), filtration (filamentous fungi), washing, drying etc.

40. vi) Processing for use as SCP a)Cell wall degradation -Liberation of cell proteins by destruction of cell wall - either by physical (Freezing –thawing, osmotic shock, heating, drying),chemical (enzymes, salts like sodium chloride, sodium dodecyl sulphate ) or mechanical (e.g. crushing, crumbling, grinding, pressure homogenization etc.) methods. b) Reduction of nucleic acid content by chemicals (acidified alcohol, salts etc.) and enzymes (nucleases).

41. CURD A fermented milk product. Curd can be used for direct consumption or for the production of butter. Chemical composition of whole milk curd is Water - 85 to 88 % Fat - 5 to 8 % Protein - 3.2 to 3.4 % Lactose - 4.6 to 5.2 % Ash - 0.7 to 7.2 % Lactic acid - 0.5 to 1.1 %

42. PRODUCTION OF CURD Curd is formed from milk. Milk contains the sugar lactose and protein casein.   Milk is inoculated with the starter culture and kept for a few hours. Lactic acid bacteria like  Lactobacillus casei , Lactobacillus acidophilus, Lactococcus lactis ,   Lactococcus cremoris , Leuconostoc etc. grow in milk and ferment Lactose sugar in milk into Lactic acid – results in coagulation of milk protein casein to form the curd. Rennin (an enzyme from calf stomach , but now produced by genetically engineered microorganisms ) can also be used to promote curd formation.

43. PRODUCTION OF VINEGAR Vinegar A mixture of 4 % Acetic acid , small amounts of alcohol, glycerol, esters, reducing sugars, pentosans , salt and other substances . Composition of vinegar depend on the nature of raw material used for the production of vinegar. Produced from fruit juices ( Apple, Grapes, Orange etc.), starchy materials (Potato, sweet potato) by heterofermentation - Alcoholic fermentation by yeast, Saccharomyces cerevisiae and acid fermentation by Acetobacter aceti .

44. TYPES OF VINEGAR Depending on the raw materials , different types of vinegar like Apple cider vinegar Wine vinegar Malt vinegar Balsamic Vinegar (from grapes) Rice Vinegar Cane Vinegar etc.

45. Initially , the fruit juice is converted into ethyl alcohol by alcoholic fermentation carried out by yeast ( Saccharomyces cerevisiae ) Ethyl alcohol is then oxidized into acetic acid by acetic acid bacteria, Acetobacter aceti , Gluconobacter sps . etc. (Acid fermentation ).

46. Methods of production of Vinegar Slow Methods a) The Home or Let alone method Fruit juices or malt liquors undergo spontaneous alcoholic and acid fermentations and form vinegar. A film of vinegar bacteria , Acetobacter aceti , called ‘mother of vinegar’ should grow on the surface of liquid and oxidize the alcohol to acetic acid. Low yield because of the absence of productive strains of vinegar bacteria Very slow method Vinegar of inferior quality.

47. b). The Orleans or French Method – for continuous production of vinegar. Carried out in barrels Continuous fermentation process One – third of the barrel is filled with a good grade vinegar as the starter culture – serves as the inoculum of active vinegar bacteria, Acetobacter aceti Raw material (wine or malt vinegar ) is added to fill the half of the barrel leaving an air space. The acetic acid bacteria growing in a film on top of the liquid carry out the oxidation of alcohol to acetic acid for weeks or months. Part of vinegar is drawn for bottling and is replaced by equal amounts of wine or alcoholic liquor.

48. 2. Quick Method - Generator Method Common method Gives high yield of good quality vinegar. Generator tanks made of wood Upper section – alcoholic liquor acidified with vinegar is introduced with a sprinkling device ( sparger ) Middle section – the liquid is allowed to trickle down over beechwood shavings or charcoal - which has developed a slimy growth of acetic acid bacteria, Acetobacter aceti – air enters through the false perforated bottom - temperature is maintained at 29 to 30 °C - oxidise the alcohol to acetic acid. Bottom section – vinegar get collected.

49. http://www.biologydiscussion.com/botany/microbes/list-of-6-important-fermented-foods/47082

50. Modern generators are equipped with automatic controls for feeding alcoholic liquid introduction of filtered air temperature control recirculation of liquid collected at the bottom etc. https://en.destiller.pl/additional-equipment/compact-vinegar-plants/small-fully-automated-vinegar-production-plant

51. 3. Submerged fermentation Vinegar is produced in Acetators by submerged fermentation. allows strict control of aeration and temperature. USES OF VINEGAR In Pickling For preservation of meats and vegetables For salad dressing. Image :https://www.frings.com/ACETATORS-Vinegar-production.64+M52087573ab0.0.html

52. Role of Microbes in Reconversion of Wastes Waste  -unwanted and unusable materials which is of no use - Solid wastes - Liquid wastes - Industrial wastes Putrescible wastes – can be disposed by microbial degradation - degraded by saprophytic bacteria and fungi - The complex organic molecules are broken down into simpler ones - Biodegradable wastes . Non- Putrescible wastes – Not degraded by saprophytic bacteria and fungi . These are non - biodegradable   wastes .

53. 1. Solid wastes : Undesirable solid or semisolid substances. Municipal solid wastes The overall garbage created by a community- include wastes from houses hotels vegetable markets fish markets butcher shops Businesses schools and other institutions etc. Municipal solid wastes Image: http://techalive.mtu.edu/meec/module15/MunicipalSolidWaste.htm

54. Hazardous solid wastes Highly dangerous wastes -toxic, explosive or corrosive and may cause potential hazard to human health and environment . Can not be handled, stored , transported, treated or disposed off without special precautions. https://www.maine.gov/dep/waste/hazardouswaste/index.html

55. Biomedical wastes Waste   generated during the diagnosis, treatment or immunization of human beings or other animals .

56. 1. Sanitory land filling Very common method  Landfills represent an environmentally acceptable disposal method of municipal solid waste on ground.  The burial of solid waste in a landfill initiates a complex series of chemical and biological reactions . The anaerobic biodegradation of solid waste requires the coordinated activity of several groups of microorganisms.  The predominant organisms participating in the degradation process of municipal solid wastes are members of the class Clostridia , Fibrobacter , Arcobacter , Pseudomonas, Acinetobacter etc.  

57. Solid wastes are dumped in successive layers, one above another, in low – lying land areas. Each layer is nearly 1.5 m thick - covered by 20 – 25 cm thick soil Keep it for 1 week – fill the next layer Waste collection vehicles compress waste so that more of it can be stored in the same space. Spraying insecticide will reduce mosquitoes, flies etc. Whole waste get stabilized in a few months and settles down by 20 – 40% of its original thickness. Hydrolysis of complex organic matter may occur under anaerobic conditions , releasing CO2, CH4, H2S and other gases and produce simple, water – soluble organic acids.

58. Sanitory land filling Image: https://www.dreamstime.com/

59. Composting Composting is the natural process of decomposing and recycling biodegradable organic materials into a humus-rich material called compost by the successive action of microorganisms. Types of Composting i ) Aerobic composting ii) Anaerobic composting

60. Types of Composting Aerobic composting Decomposition of biodegradable wastes takes place in presence of oxygen. The wetted organic matter- mixed farm residues, leaves, food wastes etc. are collected in a heap. Aerobic saprophytic bacteria  are the most important decomposers. (e.g. Bacillus subtilis , Pseudomonas sps . ). Other microorganisms like saprophytic fungi (vegetative vultures of plant kingdom eg . Aspergillus fumigatus , Penicillium sps ., Trichoderma sps . ) and actinomycetes . After a few weeks or months, these biodegradable wastes will be transformed into a dark-brown or black humus material called compost.

61. a ) Trench composting Solid wastes are deposited in trenches (4 – 10 m long, 2 – 3 m wide, 0.7 – 1.0 m deep ) in successive 15 cm thick layers sandwiched by 5 cm thick layers of semi – liquid cattle dung, until the waste heap rises to 30 cm or more above the ground level. A 5 – 7.5 cm thick layer of soil is spread over the top of the heap to prevent wind – blowing of the waste and entry of insects. Decomposition of the wastes will be completed in about 4 – 5 months and the humus – like compost is formed which can be used as manure.

62. Trench composting https://www.rapidrivermagazine.com/2017/ https://www.quickcrop.co.uk/blog/creating-a-compost-trench/

63. b) Open Air Composting Select an area free from water logging. Solid wastes are dumped on open ground as 5- 10 m long, 1 – 2 m wide and 0.5 – 1 m high piles. The top of each pile is covered with cattle dung. After a few weeks, the piles are turned upside down for cooling and aeration. The wastes will be converted into compost in about 4 – 6 weeks.

64. c) Open windrow composting Suitable method to produce large quantity of compost. The biodegradable wastes are piled in long rows (windrows). The rows of wastes are turned frequently to give proper aeration. Image:https ://jooinn.com/compost-windrow.html

65. ii) Anaerobic composting Biodegradable wastes are kept in the absence of oxygen inside a sealed tank or digester. Decomposition of the wastes are carried out by anaerobic bacteria. In anaerobic composting, the temperature of the wastes increase up to 70 °C within 7 days - This heat persists for 2-3 weeks and help for anaerobic decomposition of wastes and kill pathogenic microorganisms. Anaerobic decomposition of organic matter results in the formation of several inorganic substances such as ammonia, hydrogen sulphide , carbon dioxide, organic acids etc. Humus – like compost will be formed in about 4 – 5 months .

66. Mechanical composting Biodegradable wastes are converted into compost by mechanical devises in composting plants. Steps : Reception of wastes Segregation of wastes Shredding (Pulverization) Stabilization of the wastes – takes place in 3 – 6 days. Preparation of the stabilized mass for marketing. Image :https://teja12.kuikr.com/

67. Vermicomposting - The technique of speeding up the process of composting by the use of earthworms - the process of producing vermicompost . Earthworms eat the organic wastes and convert it into worm castings or vermicompost . – Once ingested by the worms , these organic materials undergo physical and chemical breakdown in the gut.

68. The worms secrete enzymes – proteases, lipases, amylases, cellulases and chitinases – bring about rapid biochemical conversion of the cellulosic and proteinaceous materials in the variety of organic wastes- municipal solid wastes, household garbages etc. Thus by the feeding and the casting activity the earthworms convert organic wastes into vermicompost . Earthworms commonly used in vermicomposting include Eisenia foetida E. andrie Perionyx excavates P. sansibaricus Eudrillus eugeniae Lumbricus rubellus etc.

69. VERMICOMPOSTING Image:https ://7b1a1d70-a-62cb3a1a-s-sites.googlegroups.com/ Image:https ://i0.wp.com/www.bioenergyconsult.com/ Image:https ://www.ecomena.org/vermicomposting/

70. 2. Liquid wastes Agricultural and industrial operations and human activities produce liquid wastes - include any form of liquid residue like sewage - the waste water from various sources which may contain animal excreta, domestic wastes, industrial wastes etc. The bacterium Sphaerotilus natans , popularly known as sewage fungus , play an important role in the degradation of organic matter in sewage. Sphaerotilus natans

71. 3. Industrial wastes Microorganisms can be used as bioremediators . Pesticides – Certain Microorganisms or Cell extracts or enzymes of microbes can degrade pesticides. In recent years, many scientists have enriched, isolated, cultured and screened a lot of microbial floras, such as bacteria, fungi, actinomycetes , algae and other microbial strains from the natural sewage or soil to degrade pesticides. Microbes detoxify the wastes .

72. Bacteria for Pesticide degradation : Pseudomonas Can degrade Aldrin , Chlorpyrifos , Coumaphos , Diazinon , Endosulfan , Endrin etc. Bacillus Can degrade Chlorpyrifos , Coumaphos , DDT , Diazinon , Dieldrin , Endosulfan , Endrin , Glyphosate etc. Alcaligenes & Flavobacterium Can degrade Chlorpyrifos , Endosulfan Diazinon , Glyphosate , Parathion Klebsiella , Acinetobacter , Alcaligenes , Flavobacterium , and Bacillus subtilis Can degrade Endosulfan .

73. Actinomycetes for Pesticide degradation : Streptomyces alanosinicus , Streptoverticillium album , Nocardia farcinia , Streptomyces atratus , Nocardia vaccini , Nocardia amarae , Micromonospora chalcea etc. can degrade Aldrin, carbofuran , chlorpyrifos , diazinon , diuron etc. Algae for Pesticide degradation : Green microalga Chlamydomonas mexicana can degrade Atrazin . Fungi for Pesticide degradation : Aspergillus fumigatus , A. terreus , Penicillium   citrinum , Trichoderma harzianum etc. can degrade  chlorfenvinphos .

74. Disposal of Toxic heavy metals Wastes from thermal power stations , metal refining industries, electroplating units, sewage sludge, tanneries etc. contain toxic heavy metals. Heavy metals include Mercury (Hg), Lead ( Pb ), Chromium (Cr), Arsenic (As), Zinc (Zn), Cadmium ( Cd ), Uranium (U), Selenium (Se), Silver (Ag), Gold (Au) and Nickel (Ni) - Heavy metals such as As , Cr, Pb , Hg, Cd , U, etc. are persistent components of industrial effluents. 

75. Pseudomonas fluorescens , Pseudomonas aeruginosa , Arthrobacter viscous , Citrobacter sps . etc. are used as bioremediators for heavy metal pollution. Rhizopus orrhizus can accumulate Uranium and Thorium. Penicillium chrysogenum is used for the removal of Radium. Yeast, Saccharomycetes cerevisiae can accumulate Uranium from dilute metal solution.

76. Thiobacillus thiooxidans can bring about the bioleaching of Cobalt, Nickel and Zinc from their sulphide ores. T. ferroxidans can be used in the recovery of Gold and Silver. Streptomyces flavomacrosporus   is a multi metal tolerant strain. A genetically engineered bacterium Deinococcus radiodurans can be used as a bioremediator to degrade toluene and mercury from highly radioactive nuclear wastes.

77. Disposal of Petroleum products Oil-degrading microorganisms include Pseudomonas putida (used for cleaning an oil spill in Texas, USA in 1990), Marinobacter ,    Acinetobacter etc.

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