SECONDARY SCREENING PART II

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Hello my dear pharmainfo friends, This blog is a continuation to "SECONDARY SCREENING PART I" (http://www.pharmainfo.net/dr-girija-sankar/blog/secondary-screening-part-i) by my guide. In secondary screening, the simplest method to determine antibiotic inhibition spectrum is "giant colony technique". The antibiotic say Streptomycete is streaked in a narrow band across the centre of the plates containing agar and are incubated to allow the growth. Strains of test organisms are then streaked from the edges of the plates without touching the central growth and then incubated. The distance over which the growth of each test organisms has been inhibited by antibiotic in the vicinity of the streptomycete is noted in millimeters.[1] Various nutritious media are prepared in Erlenmeyer flasks. These can be replaced by using Glass baffles which have projections into the medium from bottom or sides. These baffles provide better aeration than the former ones. The medium is prepared and sterilized in an autoclave and inoculated with one of the streptomycetes to be tested. These flasks are incubated either stationery or shaken. The latter process is desirable since enough agiatation and aeration are provided which results in better growth of the organisms. During intervals, the samples are tested for analysis. In some cases as with polyene antibiotics, the antibiotic activity is present in the mycelium of the streptomycete instead of culture broth. Special extraction procedures are to be done here.[1] In any methodology or procedure you employ, there may be chances of contamination despite of the asceptic conditions. In this case, inoculation into suitable medium is done which allows extensive growth of contaminants. The pH is another physical parameter that needs to be constantly monitored while experimentation since increase or decline of pH may effect product yield.[1] Whenever the desired product is relatively stable, it needs no special attention as we can carry out the process safely and easily. This does not mean that product instability is undesired and needed to cast away. Since in some instances products (antibiotics) are more stable in the animal or human body than as laboratory preparations.[1] Finally the antibiotic preparations (since we have taken it as an example) are purified, seperated and dried using various techniques like ion exchange resins, solvent extraction and freeze drying. The resultant product is stored in a place that prevents the product's degradation. Finally it is tested for the activity. In antibiotics, we check[1] 1. bacteriostatic or bactericidal activity against test organisms 2. The ability to precipitate serum proteins 3. The ability to cause hemolysis of blood. 4. Ability to harm phagocytes. 5. Possible occurrence of diauxie phenomenon 6. Finally Genetic studies and Mutations. Thus it is really hard and tedious process to introduce a new strain with some desired property into the market. But the vivid picture is obtained from the above two techniques. The present biotech utilizes this screening procedure to allow detection of valued microbes which find use in various ailments like Cancer- L-Asparginase, Anti infective agents by Actinomycetes. Reference 1: Reference: Industrial Microbiology L E Casida, Jr, 2007 Reprint edition, Page nos: 67-75 THIS BLOG DOESN'T CONTAIN ANY PLAGIARIZED MATERIAL
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Sirisha Pingali's picture
Author: Sirisha Pingali

Comments

SS Md Shafi's picture

Hi... what is the pH N Temperature required...??

shafi ..

Sirisha Pingali's picture

Hellow shafi Thank you for the valuable comment Bioprocess variables like pH,temperature,rpm,aeration (dissolved oxygen) depends on the organism employed for our product of interest.

Sirisha Pingali

http://www.pharmainfo.net/sirisha

Viswanadha Institute of Pharmaceutical Sciences.

www.vnips.edu.in

Gangadhar Hari's picture

Can i know what is diauxie phenomenon??

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