Class: BE210
Group: W4
Members:
Kevin Cronk
Jack Kent
Deep Maji
Chris Walstad
Date: April 2004
Abstract:
Saccaharyomyces cerevisiae, or baker’s yeast, is a common unicellular
organism with wide applications to scientific research in both academic
and commercial biotechnology. Naturally occurring in almost all
locations on earth, these eukaryotic fungi are favored in academia and
industry for their relatively simple biochemistry and their improved
compatibility with eukaryotic genes over bacteria, a characteristic
important for genetic engineering. Under favorable conditions, S.
cerevisiae reproduces through a process known as cell separation, or
“budding,” in which a daughter cell protrudes from a mother cell,
develops while still attached, and then splits from the mother cell.
This process repeats as long as growth conditions are favorable. When
growth conditions become harsh, yeast cells form sturdy spores that can
survive for a long time and germinate into actively growing yeast again
when conditions improve. The common media used for S. cerevisiae growth
is YPD Broth, a media comprised of yeast extract (Y), peptone (P), and
dextrose (D). Yeast extract is components of dead yeast cells which
primarily aids in the lag phase of yeast growth by providing ready-made
yeast components for the new cells, which are then not restricted to
producing the components from scratch. Peptone, a protein derivative,
is the primary source of amino acid building blocks for new proteins
synthesized in a growing yeast population. Dextrose, also known as corn
sugar, grape sugar, or D-glucose , is a naturally occurring form of
glucose and provides the essential nutrients and energy needed for
yeast reproduction and growth. The most common YPD Broth available
commercially is composed of 10g/L Yeast Extract, 20 g/L Peptone, and 20
g/L Dextrose. The quoted cost of YPD growth media provided in
bioengineering lab is $5.31/L. The optimization of growth media with
regard to cost and growth has many important applications in industry.
The pharmaceutical/biotechnology industry, for example, must pay close
attention to the growth media used in large bioreactors. The large
scale of those processes requires that the media be optimized for a
particular application, which can save drug companies significant
amounts of funds that can be used in more research in drug discovery.
S. cerevisiae is also used extensively in the brewery and alcoholic
beverages industry . In addition to its scientific value, detailed
knowledge of both methodology and past research data on growth
characteristics of the yeast can aid in quality control and cost
reduction in this $150 billion industry. Data on S. cerevisiae response
to varying YPD concentrations can also serve as a gauging basis for
future tests of addition nutrient’s contribution to yeast growth.