Hello viewers, After a brief introduction to General Screening Techniques in my previous blog (http://www.pharmainfo.net/dr-girija-sankar/blog/introduction-screening-t...) and Primary Screening (http://www.pharmainfo.net/sirisha/blog/primary-screening) we shall now move onto SECONDARY SCREENING. Secondary screening Primary screening helps us in identification and isolation of microorganisms that find use in industries. But it doesn't quantify the results ie. the yield obtained may not be known. Similarly the new compound may be already existing. Inorder to evaluate all such results Secondary screening should be carried out to launch a successful new and pure product.[1] In primary screening, antibiotic assay (example we chose previously) is carried out using crowded plate technique. This technique carries few limitations:[1] 1. It helps in determining the microorganisms that produces antibiotic without regard to what type of microorganisms are sensitive to the antibiotic. 2. Also the clear inhibitory zone may be due to -Decline in pH -Depletion of nutrients surrounding the colony -Rapid metabolism of the organisms. So therefore, to evaluate in a better manner we use Secondary Screening techniques. The technique is carried on agar plates, flasks or small fermentors containing liquid media. [1] Procedure carried out on agar plates is well accepted because it gives more information with less expense of energy. Moreover high effort and technical skills are not required. But to know the product yield potentials of various isolates small scale fermentors are used where they give complete nutritional, physical and production responses of an organisms.[1] TYPES OF SECONDARY SCREENING:[1] Secondary screening may be QUALITATIVE or QUANTITATIVE Qualitative: For eg tells us the spectrum or range of microorganisms sensitive to particular antibiotic Quantitative: This approach tells us the yield of antibiotics expected when microorganisms are grown on various media. Secondary screening -[1] 1. Should give all the necessary information regarding the organisms ie., family or genera to which it belong 2. Should predict the organism's pathogenicity for plants, animals, man which would need to be considered while handling. 3. Should give an idea regarding growth characteristics and other requirements. 4. Should determine whether more economical and feasible product exists than the existing one etc. To determine whether the product is newly discovered one chromatographic methods are used. To determine the product yields, the microorganisms are grown on various media for various period of times. Secondary screening should give the following information [1] 1. pH, aeration and other critical requirements associated with the organism 2. Gross genetic changes that may occur in the organism- MUTATIONS- chances of reduced yields 3. Whether any constituents in the media are missing or toxic to the organism 4. Regarding Product solubility and Chemical Solubility. 5. Regarding the structure of product - simple, complex, macromolecule 6. Whether the product possess physical properties- absorption of UV, fluorescence and chemical properties. Secondary screening should determine whether the product is biologically or optically active. Sometimes, during the production of actual product, some byproducts may also be produced in major or minor quantities. These products may not be neglected because they can be marketed as byproducts and put on sale to increase the economic position of the fermented product.[1] In another instance, the microorganisms are also capable of destroying their own fermented products by synthesizing and releasing adaptive enzymes. Good example is the amino acids production. The organism may synthesize "racemase" enzyme that will convert the L-configuration and D-configuration with the latter having little biological value. Secondary screening should pose a check on this too.[1] Reference 1: Industrial Microbiology L E Casida, Jr, 2007 Reprint edition, Page nos: 63-67. THIS BLOG DOES NOT CONTAIN PLAGIARISED MATERIAL