Strain improvement involves directed modification of biochemical pathways or introduction of new pathways using recombinant DNA to enhance industrial microbial properties and product formation. Methods for strain improvement include mutation, modifying gene expression, and recombination. Mutation can be spontaneous or induced using mutagens like UV radiation, alkylating agents, or base analogs. Gene expression is modified by altering transcription, fusion proteins, or removing feedback controls. Recombination occurs through sexual cycles, transformation, transduction, conjugation or recombinant DNA techniques. Applications demonstrated enhanced production of asperenone, salinomycin, and ethanol through mutagenesis and screening mutant strains.

1. STRAIN
IMPROVEMENT
NIKHIL AGGARWAL
Roll No.- 09010620

2. Definition
The directed improvement of product
formation or cellular properties through
modifications of specific biochemical
pathways or by introduction of new pathways
using recombinant DNA technology.

3. The need
• Heterologous protein formation
• Extension of substrate range
• Pathways leading to new products
• Reduction of by-product formation
• Improvement of yield etc.

4. Methods
• Mutation
• Modification of Gene Expression
• Recombination

5. Mutation
• Spontaneous mutations arise occasionally in
all cells and develop in the absence of any
added agent.
• Induced mutations are the result of exposure
of the organism to a mutagen.

6. Mutation contd..
Mutagens:-
• Base analogs- example 5-bromouracil (5-BU), an analog of
thymine.
• Intercalating agents- distort DNA to induce single nucleotide
pair insertions and deletions. These include acridines such as
proflavin and acridine orange.
• Alkylating agents- causes changes in a base’s structure and
therefore alters its base pairing characteristics. Example methyl-
nitrosoguanidine, that adds methyl groups to guanine, causing
it to mispair with thymine.
• UV radiation, carcinogens such as aflatoxin B1 and other
benzopyrene derivatives.

8. Modification of Gene Expression
• It is possible to modify gene regulation by
changing gene transcription, fusing proteins,
creating hybrid promoters, and removing
feedback regulation controls. These
approaches make it possible to overproduce a
wide variety of products.
• It can also be done by altering controls or
blocking enzymes in biochemical pathway.

10. Recombination
• recombination in fungi: sexual and
parasexual cycles
• recombination in bacteria: transformation,
transduction and conjugation
• in vivo rearrangements by transposable
genetic elements
• protoplast fusion
• in vitro recombinant DNA techniques

11. Applications
• The enhancement of production of asperenone , an inhibitor of
lipoxygenase and human platelet aggregation from Aspergillus niger CFTRI
1105, was achieved by UV and nitrous acid mutagenesis.
• Nitrous acid mutants exhibited increased asperenone production when
compared with UV irradiated mutants.

12. Applications contd..
• Ethanol yeast normally grows at 25- 30°C and stop growing at 40°C
while an optimum temperature for ethanol fermentation is 5-10°C
higher.
• Ethanol also has effect on microbial physiology. Its growth rate
decreases when ethanol concentration is increased.
• In order to enhance ethanol production yield in the fermentation,
improving the yeast strain by two mutagenesis techniques as UV
irradiation and chemical mutagen EMS were carried out.

14. Applications contd..
• Firstly, Streptomyces albus JCM 4703 was sequentially treated with
mutagens(UV, NTG, nitrogen mustard, etc.) to form strain SAM-X which
produces 10mg/ml of salinomycin as compared to 250 μg/ml in JCM 4703.
• Secondly, spontaneous mutants of SAM-X resistant to streptomycin,
gentamicin, or rifampin were developed. Mutants with enhanced
salinomycin production were detected from the Strr, Genr, or Rifr mutant
isolates. The most productive strains were designated KO-600, KO-602,
and KO-603, respectively.

15. Conclusion
The exploitation of cellular complexity for strain
improvement has been a challenging goal for
applied biological research. Progress in strain
improvement will depend not only on advances
in technologies for high-throughput
measurements but, more importantly, on the
development of theoretical methods that
increase the information content of these
measurements and, as such, facilitate the
elucidation of mechanisms and the identification
of genetic targets for modification.

16. Bibliography
• www.wikipedia.org
• http://www.scribd.com/doc/8801762/Isolation-Preservation-and-
Improvement-of-Industrial-Microorganism
• Microbiology by Lansing M. Prescott, 5th Ed.
• Bioreaction Engineering Principles by John Villadsen
• Research Papers:-
1. Innovative Approach for Improvement of an Antibiotic-Overproducing Industrial Strain
of Streptomyces albus (Norimasa Tamehiro, Takeshi Hosaka, Jun Xu, Haifeng Hu,
Noboru Otake, Kozo Ochi)
2. Strain improvement of Aspergillus niger for the enhanced production of asperenone
(C. Chidananda , C. Mohan Kumar , A. P. Sattur)
3. Strain Improvement of Ethanol Fermenting Yeast Using Random Mutagenesis
Technique (Teerapatr Srinorakutara, Podjana Chumkhunthod, Suthkamol Suttikul,
Wandee Yindeeyoungyeon, Ladda Wattanasiritham, Bancha Mouthung and Montree
Wangpila)