Download Industrial microbiology Second level

Industrial microbiology
Second level
Lab 2 :- Fermentation
Fermentation : is a metabolic process that converts sugar to acids, gases
or alcohol. It occurs in yeast and bacteria, but also in oxygen-starved
muscle cells, as in the case of lactic acid fermentation. Fermentation is
also used more broadly to refer to the bulk growth of microorganisms on
a growth medium, often with the goal of producing a specific chemical
product. French microbiologist Louis Pasteur is often remembered for his
insights into fermentation and its microbial causes. The science of
fermentation is known as zymology.
Aerobic respiration: requires oxygen (O2) in order to generate ATP.
Although carbohydrates, fats, and proteins are consumed as reactants, it is
the preferred method of pyruvate breakdown in glycolysis and requires
that pyruvate enter the mitochondria in order to be fully oxidized by the
Krebs cycle. The products of this process are carbon dioxide and water,
but the energy transferred is used to break strong bonds in ADP as the
third phosphate group is added to form ATP (adenosine triphosphate), by
substrate-level phosphorylation, NADH and FADH2
Anaerobic respiration:- is used by some microorganisms in which
neither oxygen (aerobic respiration) nor pyruvate derivatives
(fermentation) is the final electron acceptor. Rather, an inorganic acceptor
such as sulfate or nitrate is used. Such organisms are typically found in
unusual places such as underwater caves or near the lava shoots at the
bottom of the ocean.
Alcoholic fermentation, also referred to as ethanol fermentation, is a
biological process in which molecules such as glucose, fructose, and
sucrose are converted into cellular energy and thereby produce ethanol
and carbon dioxide as metabolic waste products. Because yeasts perform
this conversion in the absence of oxygen, alcoholic fermentation is
considered an anaerobic process.
Alcoholic fermentation occurs in the production of alcoholic beverages
and ethanol fuel, and in the rising of bread dough.
Alcoholic fermentation is the conversion of sugar into carbon dioxide gas
(CO2) and ethyl alcohol. This process is carried out by yeast cells using a
range of enzymes. This is in fact a complex series of conversions that
Industrial microbiology
Second level
brings about the conversion of sugar to CO2 and alcohol. Yeast is a
member of the fungi family which I like to think of as plants but strictly
they are neither plant nor animal. To be specific yeast is a eukaryotic
micro-organism. Not all yeasts are suitable for brewing. In brewing we
use the sugar fungi form of yeast. These yeast cells gain energy from the
conversion of the sugar into carbon dioxide and alcohol. The carbon
dioxide by-product bubbles through the liquid and dissipates into the air.
In confined spaces the carbon dioxide dissolve in the liquid making it
fizzy. The pressure build up caused by C02 production in a confined
space can be immense. Certainly enough to cause the explosion of a
sealed glass bottle. Alcohol is the other by-product of fermentation.
Alcohol remains in the liquid which is great for making an alcoholic
beverage but not for the yeast cells, as the yeast dies when the alcohol
exceeds its tolerance level.
The overall process of fermentation is to convert glucose sugar (C6H12O6) to
alcohol (CH3CH2OH) and carbon dioxide gas (CO2). The reactions within
the yeast cell which make this happen are very complex but the overall
process is as follows:
C6H12O6 ====> 2(CH3CH2OH)
stored in ATP)
Sugar ====>
Alcohol
(Glucose)
(Ethyl alcohol)
+
2(CO2) + Energy (which is
+ Carbon dioxide gas + Energy
Lactic acid fermentation is a biological process by which glucose and
other six-carbon sugars (also, disaccharides of six-carbon sugars, e.g.
sucrose or lactose) are converted into cellular energy and the metabolite
lactate. It is an anaerobic fermentation reaction that occurs in some bacteria
and animal cells, such as muscle cells.
Baker’s yeast production
Marketed in the form of cake, powder or cream
Saccharomyces cerevisiae
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Most commonly used organism
Unicellular
Rich in protein & vitamin B
Budding
Industrial microbiology
Second level
Enzymes
 Maltase; converts maltose to glucose
 Invertase; sucrose to glucose & fructose
 Zymase complex; sugars to CO2 & ethanol
Process Biochemistry
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Grow either in the absence or presence of O2
Grows efficiently… O2 present
Grows inefficiently… O2 not present
Produces ethanol in large quantity
Fed-batch is best method
Incremental feeding & high aeration
Isolating saccharomyces cerevisiae yeast from natural sources
1. Samples collected from different natural sources such as soil and
fruit.
2. Make a series of dilution of the sample, then moved to the culture
media to isolate yeasts such as yeast extract agar or malt extract
agar.
3. incubated for 2-5 day at 25-30°C.
4. Get a pure culture for yeasts through a two or more on the same
media.
Types of Baker’s Yeast
1- Cream Yeast
 Suspension of yeast cells
 Cream yeast is not termed as baker’s yeast but is a marketable
product
 Solid contents about 18-20%
2-Compressed Yeast
 Solid contents range between 27-33%
 Compressed yeast can be granular or in the form of cake
1-Granular Yeast
Industrial microbiology
Second level
 Small granules
 Can be added to driest doughs
2-Cake Yeast
 Also known as active dry yeast
 Long shelf life
 Cells encapsulated in a thick jacket of dead cells
Shelf life of compressed yeast is about 1-2 years.
Bread and Bread-Making:
● Made by mixing water, flour, salt and yeast
Importance of Yeast
● It provides the CO2 needed in order for the dough to expand
● It strengthens bread dough
● During fermentation, yeast provides the metabolites necessary for
the characteristic flavour of bread
Methodology
● Measured:
- 1 mg of yeast + 50 mg of flour
-30 ml of distilled water
Industrial microbiology
Second level