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With the new facet of webpage and with a corner of happiness that Sirisha had won the pharma puzzle, i am presenting my blog "PRESERVATION OF STOCK CULTURES". Microorganisms which have ability to carry new fermentations or which provide higher yields with the existing fermentations are of value only if they are stored properly preserving their growth and productive capacities. Hence preservation of stock cultures are very important industrially and research development.[1] Various methods of preserving stock cultures:[1] 1. Agar slants/broth 2. Sterile soil 3. Mineral oil treatment 4. Lyophilization AGAR SLANTS/BROTH:[1] Agar slants are mostly commonly used for the preservation of stock cultures. The organism is taken from the master culture. After the sterilization process agar slants are prepared by placing them on slightly inclined position. Students often commit mistakes at this point. The slanting position is should be carefully adjusted. Too much inclination ie., approaching 180oC should be avoided as the hot agar may flow and wet the cotton plug. Contamination after sterilization is strictly prohibited as this may result in growth of undesired organisms.

Soon after preparing slants they are allowed to solidify. On these slants, the organism is streaked under aseptic area in Laminar Air Flow Unit and incubated for bacteria, left at room temperature in case of Actinomycetes/Fungi.

Similarly the organism suspension is prepared and the inoculated in the sterilized broth medium and maintained. MINERAL OIL TREATMENT:[1] Agar slants or stab cultures of many microorganisms can survive for a longer period of time by application of overlay of mineral oil. The mineral oil added serves the following functions: 1. Provides dissolved oxygen 2. Prevents drying of the agar 3. Decreases the metabolic rate of the organisms PRESERVATION IN STERILE SOIL:[1] Sterile soil has found wide use in preservation cultures that form "spores". These are prepared by mixing enough sand with a rich garden soil to make it friable and easy to handle. A small amount of Calcium Carbonate may be added and the mixture is transferred to screw capped tubes or tubes plugged with cotton. The tubes are autoclaved until complete sterility through random checks has be accomplished.

To this thick suspension of spores is added to the sterile soil. Moisture is removed by quickly placing the cap and maintaining reduced pressure over a drying agent.

LYOPHILIZATION:[1] This process is also known as freeze drying technique. The cells in the glass ampoules are added to the protective agent such as bovine serum and rapidly frozen at low temperatures and dried in high vacuum. The ampoules are later sealed and stored at low temperatures. If this process is done carefully, Lyophilization is the best method to preserve stock cultures because of low risks of contamination and high purity. Ref1: Industrial Microbiology by LE Casida,Jr, New Age International {P}Limited, Publishers, 2007 reprint edition Page no 114-116. THIS BLOG DOES NOT CONTAIN PLAGIARIZED MATERIAL..

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Sirisha Pingali's picture

sir This blog is very useful for basic understanding of what we are doing in Microbiology and Biotech labs.Well explained!

Sirisha Pingali

Viswanadha Institute of Pharmaceutical Sciences.

Dr Girija Sankar's picture

Thank you sirisha!

Dr.G.Girija Sankar, Associate Professor Department of Pharmaceutical Biotechnology, College of Pharmaceutical Science, Andhra University.

Siva Mavuduru's picture

Excellent work sir. I have a small doubt. how mineraloil treatment decrease metabolic rate?
Dr Girija Sankar's picture

thank you siva!! Coming to your doubt, mineral oil treatment varies the ability to grow and produce acid or gas production by microbes and thus lowers the metabolic rate.

Dr.G.Girija Sankar, Associate Professor Department of Pharmaceutical Biotechnology, College of Pharmaceutical Science, Andhra University.

Andhavarapu Bhavani's picture

Nice presentation sir. I have a doubt sir Hw can we preserve anaerobic bacteria by using mineral oils.


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