Lesson 4 - Yeast Biochemistry
This lesson describes the biochemical pathways that explain the activities of yeast in brewing. It begins by looking at what metabolism is and how we control it. It then looks at how nutrients, including sugar, are taken up by brewing yeast. Next, it explores metabolism in more detail, focusing on sugar metabolism and looking at two particular modes of metabolism, respiratory and fermentative. Finally, it considers the need for redox control and takes a brief look at gluconeogenesis and the storage of carbohydrates in yeast.
Uptake of Nutrients in Brewing Yeast
A cell membrane forms the barrier between the inside of the cell and the outside. This section describes how nutrients cross the membrane and enter the cell, looking in particular at sugar uptake.
Wort is a natural medium which contains hundreds of different chemicals, many of them potential nutrients for yeast cells. We have discussed already that one of the strengths of brewing yeast is that it can utilise a wide range of nutrients.
What do you think a yeast cell would do if it came out of a yeast storage vessel, where it has been starved, and were suddenly pitched into warm oxygenated wort, where it is then faced with a huge range of different sources of carbon, nitrogen, and other nutrients that it needs for growth?
Give yourself 5-10 mins to think about this and then click Next to continue with this lesson.