Microbial synthesis of ethanol by Zymomonas mobilis subsp. mobilis

Principle

The properties of the micro-organism Zymomonas mobilis have been used in the production of alcohol for centuries. Nevertheless, the bacterium in palm wine and pulque, the fermented juice of the agave plant, was not identified and recognised as being responsible for their alcoholic fermentation until the twentieth century. Zymomonas was found to synthesize ethanol much more effectively than yeast does. In this experiment, Zymomonas mobilis is grown in a bioreactor. The medium is blended by means of a magnetic stirrer and its temperature is controlled by means of a heating coil and a water bath with thermostats. The discharge of used medium and the supply of fresh medium can be dispensed with. This is a so-called 'static culture' (batch culture). The cell density can first be determined photometrically in the samples taken and the cell count can be determined in the counting chamber, and those data can be used to generate a growth curve. Chemical and enzymatic tests show the consumption of glucose and the production of ethanol. The experiment is easy to perform. It does not take long to prepare. The evaluation of the test results is very conclusive and clearly illustrates the methods of biotechnology.

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