Methods of Measuring Microbial Growth.docx - Methods of...

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Methods of Measuring Microbial Growth : There are different methods of counting microbial growth. These are based on different parameters of cells such as dry-weight and wet-weight measurement, absorbance, cell plate, density, turbidity, ATP measurement, viable count, ATPase activity and use of Coulter counter. (a) Wet Weight Measurement: Measuring cell mass is an easy step of cell growth measurement. A known volume of culture sample from the ferment or is withdrawn and centrifuged, Wet weight of pellets is measured by using pre-weighed filter paper. A pre-weighed filter paper of similar size is used to subtract the weight of wet filter paper. Thus wet-weight of cells is calculated. (b) Dry Weight Measurement: The cell mass of a very dense cell suspension can be determined by this technique. In this technique, the microorganisms are removed from the medium by filtration and the microorganisms on filters are washed to remove all extraneous matter, and dried in dessicator by putting in weighing bottle (previously weighted). The dried microbial content is then weighted accurately. This technique is especially useful for measuring the growth of microfungi. It is time consuming and not very sensitive. Since bacteria weigh so little, it becomes necessary to centrifuge several hundred millions of culture to find out a sufficient quantity to weigh.

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