Student Project - Investigating Autolysis

This is a SAPS student project starter, for Biology students studying A-levels, Scottish Highers and IB who are planning their independent investigation or extended projects. It contains ideas for investigations on a topic, and outlines of the scientific techniques needed for these investigations.

Yeasts are versatile micro-organisms which have been used for centuries by man to produce bread and alcoholic drinks. The yeast goes through a series of different treatments to develop the huge variety of different end products. All of these treatments involve the process of autolysis and are examples of what is known as Downstream Processing. The yeast products may be powders, granules or pastes and they are then incorporated into processed foods to provide natural flavourings.

This process of AUTOLYSIS (auto-self; lysis-splitting) involves killing the yeast and encouraging the breakdown of the cells by enzymes. These may be the cells own endogenous enzymes or enzymes may be added. It is these products of enzyme degradation which produce the specific flavour molecules. Autolysis usually begins with the addition of salt to the cells, causing water to leave the cells by osmosis and beginning the process of cell breakdown. The cells are then heated encouraging further breakdown of the cells.

In the process of autolysis it is important to try to find at what point in the process the cells actually die. You can salt and heat yeast and the test the viability by plating the treated yeast out to see if it will grow and testing the autolysed product to see if the dehydrogenase enzymes are active and you can test to see if the yeast cells can pump out methylene blue dye.

Download the full project information from the link on the right.