Strain Improvement

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Strain Improvement

  1. 1. Your logo STRAIN IMPROVEMENT 1
  2. 2. INDE X•Introduction Your logo•Process involved Selection of natural variants Selection of induced mutants The use of recombination systems•Important characteristics for strain improvement The selection of stable strains The selection of strains resistant to infection The selection of non-foaming strains The Selection of strains which are resistant to components in the medium The selection of morphologically favourable strains The selection of strains which are tolerant of low oxygen tension The elimination of undesirable Products from a production strain The development of strains producing New fermentation products•Conclusion•Reference 2
  3. 3. Introduction:Strain: A strain is a subgroup of a species with one or more Your logocharacteristics that distinguish it from other subgroups ofthe same species. Each strain is identified by a name, number,or letter.For example: E. coli strain K12, E. coli strain 0157:H7 [Ref: Jacquelyn G. Black (pg no. 242), Tortora (Pg. no. 18)]Strain improvement:The science and technology of manipulating and improvingmicrobial strains, in order to enhance their metaboliccapacities is known as Strain Improvement. [Ref: www.indianscience.in] 3
  4. 4. Process of strainimprovement: Your logo Selection of Selection of induced natural variants mutants Use of recombinant technology [Ref: Stanbury, Principles of fermentation technology 4
  5. 5. Selection of naturalvariants Your logoKeywords:  Genetic changes  Cell division  Variants  Mycelial organisms  Heterokaryons  Homokaryons [Ref: Stanbury, Principles of fermentation technology 5
  6. 6. Selection of induced mutants Your logo• The selection of induced mutants synthesizingimproved levels of primary metabolites:The levels of primary metabolites in micro-organisms areregulated by Feedback control systems.The major systems involved are feedback inhibition andfeedback repression. [Ref: Stanbury, Principles of fermentation technology 6
  7. 7. Your logo FIG.1.1 The control of a biosynthetic pathway converting precursor A to end product E via the intermediates B, C and D. [Ref: Stanbury, Principles of fermentation technology 7
  8. 8. Concerted Your logo or multivalent feedbackcontrol: FIG.1.2 The control of a biosynthetic pathway by the concerted effects of products D and F on the first enzyme of the pathway. [Ref: Stanbury, Principles of fermentation technology 8
  9. 9. Co-operative feedback control Your logo FIG. 1.3 The control of a biosynthetic pathway by the co- operative control by end products D and F. [Ref: Stanbury, Principles of fermentation technology 9
  10. 10. Cumulative feedback control Your logo--- 50% ---- Inhibition of 50% of the activity of the enzyme------ Total inhibition of enzyme activityFIG.1.4 The control of a biosynthetic pathway by the cumulative control ofproducts D and F. [Ref: Stanbury, Principles of fermentation technology 10
  11. 11. Sequential feedback control Your logo FIG.1.5 The control of a biosynthetic pathway by sequential feedback control. [Ref: Stanbury, Principles of fermentation technology 11
  12. 12. Isoenzyme control Your logo Fig.1.6 The control of two isoenzymes (catalysing the conversion of A to B) by end products D and F. [Ref: Stanbury, Principles of fermentation technology 12
  13. 13. •The isolation of mutants which do not producefeedback inhibitors or repressors: Your logo Fig.1.7 Overproduction of primary metabolites by decreasing the concentration of a repressing or inhibiting end product. 13
  14. 14. •Examples of the use of auxotrophs for theproduction of primary metabolites: Your logo FIG. 1.8. The control of the aspartate family of amino acids in C. glutamicum. 14
  15. 15. The use of recombination systems for theimprovement of industrial micro-organisms Your logo• Recombinant DNA techniques – In simple words, rDNAtechnique can be explained as, bringing together in oneorganism, genes from several organisms, has the potential fornot only increasing yields but also for producing entirely newsubstances.• Recombinant DNA technology has resulted in organismsproducing compounds which they were not able to producepreviously. [Ref: Stanbury, Principles of fermentation technology] 15
  16. 16. The logo Your application of the parasexual cycle•Many industrially important fungi do not possess a sexualstage and therefore it would appear difficult to achieverecombination in these organisms.•However, Pontecorvo et al. (1953) demonstrated thatnuclear fusion and gene segregation could take placeoutside, or in the absence of, the sexual organs.•The process was termed the parasexual cycle and hasbeen demonstrated in the imperfect fungi, A. niger and P.chrysogenum, as well as the sexual fungus A. nidulans. [Ref: Stanbury, Principles of fermentation technology] 16
  17. 17. Your logoFIG. 1.9. Diagrammatic representation of the mitotic division of aeukaryotic cell containing two chromosomes. The nuclear membranehas not been portrayed in the figure. [Ref: Stanbury, Principles of fermentation technology] 17
  18. 18. •Mitotic crossing over involves the exchange of distalsegments between chromatids of homologous chromosomes Your logoshown in Fig. 1.10. FIG. 1.10. Diagrammatic representation of mitosis including mitotic crossing over. 18
  19. 19. • Haploidization is a process which results in the equaldistribution of chromatids between the progeny of a mitosis. Your logoFig. 1.11 FIG. 1.11. Diagrammatic representation of mitosis involving haploidization. 19
  20. 20. The application of protoplast fusiontechniques are cells devoid of their cell walls and may be Your logo• Protoplastsprepared by subjecting cells to the action of wall degradingenzymes in isotonic solutions. Protoplasts may regeneratetheir cell walls and are then capable of growth as normal cells.• Protoplast fusion has been demonstrated in a large numberof industrially important organisms including Streptomycesspp. (Hopwood et al., 1977), Bacillus spp. (Fodor and Alfoldi,1976) [Ref: Stanbury, Principles of fermentation technology] 20
  21. 21. The improvement of industrial strains: Your logo Although a strain may produce a very high level of ametabolite it would be unsuitable for a commercial process ifits productivity were extremely unstable, or if the organismsoxygen demand were such that it could not be satisfied in theindustrial fermenter available for the process. Therefore, characteristics of the producing organismwhich affect the process may be critical to its commercialsuccess. Thus, it may be desirable to modify suchcharacteristics of the producing organism which may beachieved by selecting natural and induced variants andrecombinants. [Ref: Stanbury, Principles of fermentation technology] 21
  22. 22. Important characteristics for strain• The selection of stable strainsimprovement Your logo• The selection of strains resistant to infection• The selection of non-foaming strains• The Selection of strains which are resistant to componentsin the medium• The selection of morphologically favourable strains• The selection of strains which are tolerant of low oxygentension• The elimination of undesirable Products from a productionstrain• The development of strains producing New fermentationproducts [Ref: Stanbury, Principles of fermentation technology] 22
  23. 23. The logoConclusion: Your selection of stable strains:•The ability of the producing strain to maintain its highproductivity duringgenetic and molecular genetic methods a A number of both culture maintenance andfermentation is a very important fermentation product yields are available to improve quality. and other strain characteristics. The methods used forExample: improvement of Johnson (1970)effective yet double the Woodruff and the strain are selected a a bitauxotrophic mutant of Micrococcus glutamicus requiring both complicated too. The main reason of using suchhomoserine and threonine and compared its lysine-producingproperties with thoseattainhomoserine auxotroph. strai that methods is to of a an improved and stable can be used at industrial or commercial level. [Ref: Stanbury, Principles of fermentation technology] 23
  24. 24. Thelogo Your selection of strains resistant to infection:•Bacterial fermentations may be affected very seriously byphage infections, which may result in the lysis of the bacteria.•A possible method for reducing of failure due to phagecontamination is to select bacterial strains which are resistantto the phages isolated in the fermentation plant (Hongo etal., 1972) [Ref: Stanbury, Principles of fermentation technology] 24
  25. 25. •The selection of non-foaming strains: Your logo• Foaming during a fermentation may result in the loss ofbroth cells and product via the air outlet as well as putting thefermentation at risk from contamination.• Thus, foaming is normally controlled either by the chemicalor mechanical means, but this task may be made easier if anon-foaming strain of the commercial organism can bedeveloped. [Ref: Stanbury, Principles of fermentation technology] 25
  26. 26. The selection of strains which are resistant tocomponents in the medium: Your logoPolya and Nyiri (1966) applied this approach to the isolationof mutants of P. chrysogenum resistant to phenylacetic acid, aprecursor of penicillin and toxic to the organism at highconcentrations. [Ref: Stanbury, Principles of fermentation technology] 26
  27. 27. The logo Your selection of morphologically favorable strains:Backus and Stauffer (1955) recognized the influence of thegenetic of a strain on the morphology of P. chrysogenum insubmerged culture and its role in controlling foaming andbroth filtration characteristics [Ref: Stanbury, Principles of fermentation technology] 27
  28. 28. The selection of strains which are tolerant of lowoxygen tension: Your logoExample, Mindlin and Zaitseva (1966) isolated a lysine-producing strain which maintained its productivity underaeration conditions which decreased the parental strainproductivity by almost a half. [Ref: Stanbury, Principles of fermentation technology] 28
  29. 29. The elimination of undesirable products from aproduction strain: Your logo• Athough an industrial micro-organism may produce largequantities of a desirable metabolite it may also produce a largeamount of a metabolite which is not required, is toxic or mayinterfere with the extraction process.• An example in the penicillin-producing strains is theelimination of the production of the yellow pigment,chrysogenein, selection of non-pigmented mutants which madethe extraction of the antibiotic much simpler (BackusStauffer, 1955). [Ref: Stanbury, Principles of fermentation technology] 29
  30. 30. The logo development of Your strains producing newfermentation products:• The isolation of organisms from the natural environmentsynthesizing commercially useful metabolites an expensive andlaborious process.• Therefore, means of producing novel compounds which maybe some industrial significance have been attempted. [Ref: Stanbury, Principles of fermentation technology] 30
  31. 31. Conclusion Your logoA number of genetic and molecular genetic methods areavailable to improve fermentation product yields and otherstrain characteristics. The methods used for theimprovement of the strain are effective yet a bit complicatedtoo. The main reason of using such methods is to attain animproved and stable strain that can be used at industrial orcommercial level. 31
  32. 32. Reference Your logo• Stanbury F. Peter , 2003, Strain Improvement, Principles offermentation technology, Great Britain by MPG Books Ltd, Bodmin,Cornwall, second Edition, Pg. 43-82.•Tortora J. Gerard, 2010, Strain, Pearson Benjamin Cummings, SanFrancisco, USA, tenth edition, Pg. no. 18•Prescott M. Lansing, 2007, Strain, The McGraw-Hill Companies, Inc.,New York,America, seventh edition, Pg. no. 425•Black G. Jacquelyn, 2008, Strain, JohnWiley & Sons, Inc., pg no.242• Net Source:  www.cheric.org  www.springerlink.com  www.jhu.edu  www.indianscience.in 32

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