Microbiology and Yeast Cell
Fermentation
Photo from Flickr.com
What are Microbes?
Microbes: Living things that must be greatly
magnified to be seen. They include
bacteria, fungi and viruses.
What is Microbiology?
• Microbiology is the study (logy) of very
small (micro) living (bio) things. One of the
most famous microbiologist is Louis
Pasteur. Pasteur performed experiments
that proved that microbes cause
fermentation.
What is fermentation?
Fermentation: A process of growing
microorganisms (microbes) to produce
various chemicals or pharmaceutical
compounds.
Fermentation of
microbes is how most
Biotechnology
companies products
such as enzymes and
medicines.
Definition from: Mapping your Future: Exploring Careers in Biomanufacturing
What is yeast?
• Yeast: A general term for single-celled
fungi that reproduce by budding.
Yeast cells under the microscope.
Yeast cells budding.
Some yeast can
ferment
carbohydrates
(starches and
sugars) and thus
are important in
brewing and baking.
Definition from: Mapping your Future: Exploring
Careers in Biomanufacturing
What do yeast cells need to
grow and survive?
Carbon (sugar source)
Nitrogen (protein source)
Vitamins
Yeast feeds on
sugar from a
variety of sources,
including fruit,
grain, nectar and
molasses.
How DID Biotech first use
microbes?
Around 4000 BC, Egyptians used the living
organism yeast to make bread. Airborne wild
yeast accidentally got their bread dough,
causing it to rise.
How does yeast affect the bread
making process?
Bread Dough is made with flour which
contains nutrients and sugar that the yeast
cells digest.
 When the yeast eats the sugar, it
gives off 2 waste (by) products:
The chemical reaction is written as
follows:
YEAST + SUGAR =
CARBON DIOXIDE & ALCOHOL
How do the by-products of yeast
fermentation influence the bread
making process?
The carbon dioxide is what makes the dough
rise and give it a light, airy texture.
The alcohol evaporates during baking and gives
off that wonderful aroma of baking bread.
The baking destroys the yeast.