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Culturing a Micro-organism using Aseptic Technique.

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Biology portfolio evidence Abdi Feizpour Culturing a Micro-organism using Aseptic Technique Introduction: Yeast saccharomyces cerevisia When a scientist is working with micro-organisms it is essential that they use the aseptic technique, as this: Ensures that their culture of the micro-organism remains pure and therefore free of other micro-organisms Unless aseptic culture techniques are followed strictly, an originally pure culture will definitely become contaminated with other unwanted species. Micro-organisms are very useful in making a large number of food and drinks and usually grown in liquid broth or a solid medium such as agar and either in a flat dish called a petri dish, or as a slope in a narrow bottle. Brewers use the yeast left over at the end of brewing to start their next brew. However, because of changes occurring to the yeast, they have to replace it with a pure yeast culture, about every ten brews. They will keep a pure culture of yeast in the refrigerator on an agar slope - we will culture it on a malt agar plate. Nutrient agar is often used in laboratories for growing micro-organisms. Agar is a jelly -like substance that melts when heated and sets when cooled, but does not contain any nutrients. The nutrients needed by the micro-organisms are moulded and dissolved into a molten agar. ...read more.


As the loop is very hot we had left it in there for a few seconds to make certain we had picked up living cells. Then we took the loop out from the bottle and flamed the neck again just before sealing it. At this point we were hoping to have picked up a film of yeast culture on the loop. Now at this point we had to quickly and carefully open the lid of the agar plate and just sufficiently enough to insert the inoculating loop. We gently stroke the surface of the agar with the loop in the design of a zig-zag shape [called streaking a plate]. Then we took a flame to the inoculating loop to kill any yeast cells on it. After that the teacher had given us sticky labels to put our names and the date down with the type of organism [yeast]. And later we sealed the agar -plate with sellotape and incubate at 30?C for two days. Finally we saw our individual plate with the Colonies of yeast on the malt agar plate. The result and evaluation: Unfortunately we got some contamination. This is the cause of bacteria coming into contact with the plate and the plate may have been open for too long or the equipment was not sterile. ...read more.


The method of choice for long-term yeast strain storage is under liquid nitrogen, a method that has been used by Scottish Courage Brewing Ltd since 1983. Master cultures were selected from existing brewery yeast populations after undergoing a range of microbiological, biochemical and fermentation tests. Franchise partners have supplied other strains. The poster will describe the 'cascade' system used by Scottish Courage for the storage of its brewing yeast strains. Agar slopes (slants) made from master cultures are prepared and quality assured following ISO 9000 accredited methodology. Batches of approximately 20 slopes are made from each liquid nitrogen straw, and a sacrificed slope undergoes testing for microbiological contamination, viability and yeast mutants (petites). In addition, the identity of each batch of slopes is confirmed using molecular biology analysis techniques such as PCR. Duplicate cultures of all yeast strains are held confidentially by the National Collection of Yeast Cultures as a back up. In all, twelve brewing yeast strain master cultures are held under liquid nitrogen at the [Scottish Courage Technical Center in Edinburgh] and are used to supply ten breweries with over 600 agar slopes between them on an annual basis. The yeast storage and supply management systems in place have proved to be robust and reliable over a number of years, giving the breweries in the group confidence in the quality of the yeast supplied to initiate brewery propagations. By Abdi Feizpour [Ms Agyepong] ...read more.

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