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Population Growth Of Yeast And Effects Of Various Substrates On This Population Growth.

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Coppice Community High School Biology Department Population Growth Of Yeast And Effects Of Various Substrates On This Population Growth Plan: 1. Introduction; Yeast is a unicellular fungus which reproduces asexually by budding or division, as in the case of the genus Saccharomyces, which is important in fermentation in food (walker, 1998). Yeasts are widely distributed in nature. Like bacteria and moulds, they can have beneficial and non-beneficial properties in food production. The most well known examples of yeast fermentation are in the production of alcoholic drinks and the leavening of bread. Although there is a large range of species of yeasts, only a few species are used in the food industry. These species are usually either Ascomycetous yeasts or yeasts that belong to the genus Candida. Unlike most Fungi yeast cells are round or oval in shape. 2. Aim- The aim of the investigation is to discover whether different substrates of carbohydrates have a direct effect on the population growth of yeast cells. This will be done by direct counting of cells by haemocytometer to discover the average count of cells. This process shall be over a time period of 5 days. ...read more.


to transfer substances from balance to tubes to mixed. 5. Procedure; N.B-A window of 15 minuets per suspension is allowed in this experiment, this time should be used in creating the dilutions and obtaining the results. This figure can be adjusted to window which is more comfortable. Pre trials for this particular experiment showed that 15 minuets were more than adequate for the setup and observations each day. 1; for a 1% yeast solution 1g dried active bakers yeast (saccharomyces cerevisae), 1g of chosen carbohydrate substrate, 100ml of distilled water. Procedure; 1. Add yeast to sugar and pour together into water. Stir and leave to incubate in a 37� water bath for 1 hour. 2. Repeat for every suspension required leaving a window of 15 minuets per culture. REMEMBER: check temperature of water bath regularly and adjust if necessary. 2. After 1 hour (the incubation period) a serial dilution is required for the first result to be recorded. Serial Dilution for A 1% Yeast Solution to A 0.1% Dilution To conduct serial dilutions firstly make up the culture stated above. Then via a pipette add 1cm� of the yeast culture to 9cm� of distilled water. ...read more.


The working area must be kept as clean as possible and in an organised manner then the samples have a reduced risk of contamination. This must be maintained throughout the investigation. 3. Reusable items must be washed thoroughly after every work session; they can then be used next time without fear of contamination. 4. Disposable items must be disposed of in the correct fashion, and all sharps must be disposed of in specialist sharps boxes/bins. Implementation and Data Presentation The counting chamber of the Haemocytometer is 0.1 mm deep. The central squared area is divided into 25 main squares, each of which is subdivided into 16 smaller squares. The volume of suspension above the smallest squares is a uniform 0.00025 mm�. So the the number of cells in the culture suspension is given by: D*N S*C Where D= dilution of original culture N= total number of cells counted S= number of squares counted C= volume of 1square The experiment is taken over 5 days, and every 24 hours a reading is taken. Raw results will be tabulated first, with headings of sample time and cell count. This shall be done for all 6 samples. The findings will then be processed to find an average cell count per day. A graph will be drawn of cell count against time in hope that a growth curve will be achieved ...read more.

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