Investigate A Factor Which Affects the Rate Of Fermentation Of Yeast This experiment is investigating one of the factors which affects the rate of fermentation of yeast. Several factors affect the rate of reaction:  Increasing the concentration. (See the lock and key theory.) If the substrate (glucose) is increased, then there would be more keys for the locks, therefore an increase in reactant concentration leads to an increase in reaction rate.  The surface area, the bigger the surface area, the faster the reaction time is, as ....