(ii) refining the fermentation process and (iii) improving the productivity of the strain. Generally, major improvements arise from the last approach; therefore, all fermentation enterprises place a considerable emphasis on this activity. The techniques and approaches used to genetically modify strains, to increase the production of the desired product are called strain improvement or strain development. Strain improvement is based on the following three approaches: (i)mutantselection, (ii)recombination, and (iii) recombinant DNA technology. Approach Chief feature Example/Remark The main approach to strain A. Mutant Selection : improvement; produces new alleles Types of existing genes Used in, the initial stages of strain Occur without any treatment 1. Spontaneous Mutations improvement; also for maintenance with a mutagen of improved strains Induced by chemical Mutagenesis followed by selection; 2. Induced Mutations (mainly) or physical several cycles employed mutagens Production of 6-demethyl Affect the pattern of 3. Major Mutations tetracycline in place of tetracycline metabolite production by S. aureofaciens Small gains in each cycle of Affect the rate metabolite 4. Minor Mutations selection; substantial improvement production after several cycles B. Mutant Selection :Strategies Enhanced production of an amino Defective biosynthesis of a 1. Auxotrophic mutants acid, e.g., phe mutants accumulate biochemical tyrosine 2. Analogue resistant Feedback insensitive Overproduction of metabolites, mutants enzymes e.g., amino acids by C. glutamicus Some mutants are high producers, 3. Revertants of e.g., chlortetracycline by S. nonproducing mutants viridifaciens 4. Revertants of Some are high produces, e.g. auxotrophic mutants chlortetracycline by S. viridifaciens
(ii) refining the fermentation process and (iii) improving the productivity of the strain. Generally, major improvements arise from the last approach; therefore, all fermentation enterprises place a considerable emphasis on this activity. The techniques and approaches used to genetically modify strains, to increase the production of the desired product are called strain improvement or strain development. Strain improvement is based on the following three approaches: (i)mutantselection, (ii)recombination, and (iii) recombinant DNA technology. Approach Chief feature Example/Remark A. Mutant Selection : Types The main approach to strain improvement; produces new alleles of existing genes 1. Spontaneous Mutations Occur without any treatment with a mutagen Used in, the initial stages of strain improvement; also for maintenance of improved strains 2. Induced Mutations Induced by chemical (mainly) or physical mutagens Mutagenesis followed by selection; several cycles employed 3. Major Mutations Affect the pattern of metabolite production Production of 6-demethyl tetracycline in place of tetracycline by S. aureofaciens 4. Minor Mutations Affect the rate metabolite production Small gains in each cycle of selection; substantial improvement after several cycles B. Mutant Selection :Strategies 1. Auxotrophic mutants Defective biosynthesis of a biochemical Enhanced production of an amino acid, e.g., phe mutants accumulate tyrosine 2. Analogue resistant mutants Feedback insensitive enzymes Overproduction of metabolites, e.g., amino acids by C. glutamicus 3. Revertants of nonproducing mutants Some mutants are high producers, e.g., chlortetracycline by S. viridifaciens 4. Revertants of auxotrophic mutants Some are high produces, e.g. chlortetracycline by S. viridifaciens
1329236244Fermentaion%20products.docx