Class: BE210
Group: T6
Members:
Date: April 2004
Abstract:
Many
biotechnological processes used in industry bank on the reliable and
cost-effect production of Saccharomyces cerevisiae,
commonly
known as Baker's Yeast. Yeast can grow in the presence of just sugars,
which
provide a source of glucose. However, yeast grows much faster when
provided
with proteins as well as biotin, trace metals, and salts, which are
needed for
growth. Proteins, which serve to provide amino acids as well as perform
enzymatic activities, can be supplied through peptone—partially
digested
proteins. Yeast extract is obtained by the autolysis of yeast cells,
and
therefore, provides growing yeast with all the necessary components,
including
biotin, trace metals and salts, as well as proteins.
Although yeast has been proven to
grow effectively with just dextrose, previous experimentation has
suggested
that the yeast extract has the most significant effect on the
reproduction of
yeast. “The addition of protein and yeast cell extract hydrolysates
allow
faster growth so that during exponential or log-phase growth, the cells
divide
every 90 minutes.”
Moreover, during the lag phase secondary metabolites required for
growth are
produced. Since the yeast extract contains ready-made secondary
metabolites it
reduces the time required for the lag phase to transition into the log
phase.
Cost-efficiency of yeast growth is relevant in several sectors of industry. Yeast is used as a fermenting agent in bread-making, wine-making, the production of cheese and yogurt, and the production of various other foods that require fermentation. Besides fermentation, yeast can be used to create yeast extract spread for direct consumption. It is in the best interest of industrial manufacturers to determine the specific combinations of yeast extract, peptone, and dextrose that produce the desired results according to each manufacturer’s financial situation and/or demand for their product.