Fermentable and non-fermentable sugars - A simple experiment of anaerobic metabolism

The main objective of this class experiment is to show the time-dependent consumption of a fermentable sugar ( glucose) in the presence and absence of a non-fermentable sugar ( xylose) by bacteria in anaerobic conditions. The observation of the pH decrease due to acid production and the turbidity increase as a result of cell multiplication, both in function of time, enables an interesting discussion regarding the metabolic pathways and the products of anaerobic fermentation of carbohydrates. Also the time-dependent disappearance of glucose due to its metabolic consumption is compared with the non-disappearance of xylose and permits a discussion of the function of glycolysis and pentose phosphate pathways as metabolic routes.