DNA-lab “Racing on toilet paper”

How to make yeast use plant waste to produce alcohol?

Fuel prices are rising because it is becoming harder to find new sources of oil. At the same time the demand for fuels is strongly increasing, especially in South-East Asia. Apart from the price of fuel there is another important concern: Each kilometer driven using fossil fuels contributes to the emission of carbon dioxide and therefore to the greenhouse effect.

Biofuels

A possible solution to the problems mentioned above is the use of bio-fuels. These fuels are produced from agricultural products and waste materials. An example is bio-ethanol from corn, sugar beet or sugar cane. In a fermentation process, the sugars from these crops are turned into alcohol (ethanol). Because the crops can be cultivated repeatedly, they provide an unlimited supply of raw material in contrast to a limited supply of crude oil. Another major difference is that, compared to normal petrol, bio-fuels do not cause the emission of new greenhouse gas.

Yeast DNA

How are bio-fuels linked to DNA? The connection lies in the conversion of the plant sugars into ethanol by yeast, a micro-organism that eats the sugar and produces the ethanol. This is a natural process for yeast. But to make bio-fuels affordable for everyday use, we need the yeast to be able to produce more alcohol and to do it faster. To achieve this, we can change the genetic properties of yeast. However, to target the right genes, we need to know the relationship between the yeast DNA and the production of ethanol.

Techniques

In this DNA-lab the students themselves produce bio-ethanol using yeast and toilet paper. They will study the effects of enzymes on the overall production process and they will determine the production rate of the cells by measuring carbon dioxide emissions. The students will also consider the question of how to meet the increasing demands for bio-fuels, especially in small countries with limited farmland. Using the results of their experiment, the students will argue how genetic changes in yeast affect the production of ethanol.

Required knowledge

During the practical the students will cultivate yeast cells on plant sugars and will measure the effects of genetic changes on ethanol production process in the cell. The required knowledge relates to:

Social / biotechnological aspects
• The student should be familiar with the carbon cycle and the fact that human activity (combustion) is contributing to the greenhouse effect.
• The student should know that plants, using photosynthesis, absorb carbon dioxide from the air during their growth.
• The student understands that we can modify the genetic material of (single-celled) organisms to improve specific properties.

Cellular level
• The student should be familiar with the subcellular structure of eukaryotic cells, in particular the functions of the following organelles: nucleus (gene regulation), mitochondria (ATP-production), endoplasmic reticulum (transport) and ribosomes (protein synthesis).
• The student should know that each cell synthesizes organic compounds, which are subsequently used as building blocks or fuels. During this process, the cell generates waste that is discarded.

Molecular level
• The student should understand the function of proteins and be able to describe that enzymes are specific proteins that enable certain metabolic processes in the cell take place (they catalyse specific reactions).
• The student can describe the process of protein synthesis and the role of DNA and mRNA in this process, including transcription and translation.
• The student understands that proteins can also bind to DNA and thus influence the transcription of genes (either stimulate or suppress).

Basic chemistry knowledge
• The student is able to work with chemical equations.
• The student can convert the volume of a compound into mass and vice versa, using the concept of molecular weight.
• The student can solve dilution problems, using the concepts of concentration, density and mass.
• The student is familiar with the Boyle’s law of gasses that connects moles to volume of a gas at a given temperature and pressure.

This DNA-lab can be used in both biology and chemistry lessons.