Yeast, the Basics & Background

This is a portion of an image of Dry Lager yeast placed in a micro titer plate, with 20% malt extract. The cells are at 10X magnification and are about 5 microns in diameter. and after 10 hours… Yeast is a single cell fungi used in many different fields, from cooking to cellular research to beer and wine making. Since I make beer and we generally look at cells under a microscope here at Kairos Instruments, it seemed like a good area for some further study. Turns out there are a lot of different types of fungi – 1.5 million species, and there are 1,500 species of yeast alone. Fungi are a different classification from plants, animals and bacteria. The main difference is the cell wall contains chitin whereas cell walls of plants contain cellulose, and animals actually lack a rigid cell wall. Chitin is a long chain polymer, a derivative of glucose. This polymer is also the exoskeleton of many crustaceans like crabs and shrimp. Yeast is a small cell, 3 to 7 microns in diameter, 7 microns = .00027 inches. Some yeast cells reach 40 microns in diameter, .0016 inches. Many of these cells derive their energy from fermentation, a chemical conversion of carbohydrates to ethanol and carbon dioxide. The process of using yeast as an industrial organism, that is to produce alcohol, is over 4,000 years old. Yeast was first observed under a microscope by Anthony van Leevwenhoek (1632-1723), “layu-wen-hook”.  Anthony was the first to see blood … Continue reading

Yeast Experimentation

In dealing with a cell like yeast, it occurs to me that there are a lot of questions in my mind about what causes yeast to grow. All cells need the proper environment to grow. They need food, the correct temperature and the right fluid / gas exchange. Given the proper environment, cells will divide, consuming nutrients and producing a preferred product. For yeast, the product would be CO2 for baking, or alcohol in beer making. Different types of yeast you would assume would need different food and may change characteristics based on the environment. We know in our work at Kairos Instruments, that hematopoietic stem cells for example are said to need a niche, a special place, to grow and divide to produce cells for our blood system. In the case of yeast, an environment without oxygen allows the cell to consume sugar and produce alcohol, but in the presence of oxygen, no or little alcohol is produced. So, environmental conditions effect the outcome of cell division. A question to be answered then is what nutrients and how much are needed to establish good growth. A second issue is the temperature. Most lager yeasts need a colder temperature to work properly and most ales work best around room temperature. Changes in temperature affect the yeast efficiency and in many cases the flavor component will also be affected. The next issue in my mind is the amount of yeast present in the experiment. In many cell types, if the starter … Continue reading