Respiration: making use of microorganisms

What do bread, cheese and ginger beer have in common? To be produced, they all rely on microorganisms and the process of fermentation. Consequently, these foodstuff examples are often used in classrooms to explain anaerobic respiration in yeast and bacteria. So, alongside classic bread and beer making experiments, we have compiled some extra resources to add some innovation to your lessons. The experiments included are suitable for a range of age groups, some of which can be carried out in 15 minutes and others that could span the course of a few lessons.

Respiration, the metabolic process by which we get energy from food is clearly an essential process in all living organisms. What may be less obvious, however, is how we benefit from this process in microbes. Without bacteria or yeast our fridges may look somewhat less appetising; no bread, cheese, yoghurt, wine or beer! But what role do microorganisms actually play in food production? The basic concepts of aerobic and anaerobic respiration in microbes can be illustrated by the short TED-Ed video below. Using fluffy bread, holey Swiss cheese and sour vinegar as examples, students can understand how the use of microorganisms, and the way in which they respire, results in these distinctive foods.  

Your students can turn the classroom into their own biotechnology laboratory to help you introduce the concept of microbes, and to understand what happens when yeast feed off sugars. This Science in School article provides various activities that can be incorporated around bread making, and this ginger beer recipe will introduce younger students to the principles of fermentation and the biochemistry of respiration. The “Microbial Foods” website provides some fantastic resources for teachers, including “microbe guides” for important microorganisms in foods, and a “how-to” article on using a microscope to explore fermented foods. And, if that’s not enough information on fermentation for one day, this article will provide you with ‘Everything you always wanted to know about fermented foods’.  

As a contrast to the more conventional uses of yeast, microbes can also be used to produce electricity. Using oxidation-reduction reactions, a microbial fuel cell can convert chemical energy to electrical energy. The fuel cell described in this Science in School article generates electricity by diverting electrons from the electron transport chain of yeast. Although microbial fuel cells have been around since the 20th century, it is only in recent years that the potential applications for these bacterial batteries have been put to good use. In 2007, for example, scientists and Foster’s Brewery in Australia joined forces to use a microbial fuel cell, or “beer battery”, to produce electricity from the brewery’s waste water - now that’s really making the most of microorganisms! 

We hope these articles have inspired you to carry out some novel experiments on the classic topic of respiration. And, if you find yourself lesson planning one evening, wine, cheese or beer could aptly be incorporated, all in the name of respiration!