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Industrial Microbiology& Fermentation (BT203)
Fermentationof
Carbohydrates T! "ima M !#ram
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Metabolism
It refers to the chemical reactions thatoccur $ithin the cells
of li%ingorganisms
Those reactions are catalyed by'rotein molecules called
enymes
The identication of bacterial strain isaided by
determining suchbiochemical reactions
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According to the metabolic function,bacteria are classied
into:
1- Oxidative bacteria:-
tilie o*ygen to yield carbon dio*ide and$ater
2 -Fermentative bacteria:-
tilie organic com'ounds for energy
Instead of 'roducing only C+2 and $ater,they 'roduce
complex end 'roducts, such
as acids, aldehydes, and alcohols as $ell as%arious gases, such
as carbon dio*ide,hydrogen and methane eg
-tre'tococcus,.actobacillus and / coli
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Fermentation of Carbohydrates
Bacteria often use carbohydrates asenergy sources
/ach bacterium has a collection ofenzmes that allo$s it to
utilie di%ersecarbohydrates
Carbohydrates could be 1 Monosaccharides eg glucose,
fructose
1 isaccharides eg lactose, sucrose
1 olysaccharides eg starch, cellulose
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Figure 4 Ty'es of Carbohydrates
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isaccharides and 'olysaccharidesare monomers lin#ed by
glycosidicbonds
Bacteria must 'roduce enymes
that clea%e these bonds in order totrans'ort the sugar to the
cell andutilie it
If the bacteria cannot 'roducethese enymes then the
com'le*carbohydrate is not used !"ofermentation#$
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Fermentati%e degradation of %ariouscarbohydrates by microbes
underanaerobic conditions results in the'roduction of acids
and5or gases
%o& &ould '(no&?!
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To #no$ $hether a bacteria couldutilie a certain sugar,
'roducts offermentation are tested by anindicator in a fermentation
tube
! fermentation tube is a culturetube that contains a urham6s
tube(a small tube 'laced in an in%erted
'osition in the culture tube) for thedetection of gas 'roduction
as anend 'roduct for the metabolism
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urham6s Tube -ugar Fermentation
)rocedure:
4 re'are 3 di7erent #inds of sugar media (8lucose,-ucrose,
.actose) o not forget the control for youre*'eriment 9:
2 !dd to each test tube 'henol red indicator (';indicator)
3 !dd a urham tube to each test tube
oC using sha#er incubator(43= r'm)
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?our tas#:
*ample +ontro
l
Fermentation @ @ 1
Color ?ello$ ?ello$ "ed 9
8as yes yes Ao 9
Bacteria ty'e Fermentati%e Fermentati%e +*idati%e 9
icture
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+bser%ation
)ossible reactions in fermentation tube:
a) Aegati%e reaction is indicated by the unchanged
red color of 'henol red indicator
b) ositi%e reaction $here 'henol red changes colorto yello$ due
to acid 'roduction
c) ositi%e reaction $here there6s a color changeand a gas is
tra''ed in the urham tube
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Figure 2 The 'ossible results after a carbohydrate
fermentation e*'eriment
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ossible "esults
! The inoculated bacteria couldferment the sugar to
'roduce an
acid and C+2 gas in themedia(ositi%e "esult)
B The inoculated bacteria is not afermentati%e one so no
reactiontoo# 'lace(Aegati%e result)
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?our tas#:
*ample +ontro
lFermentation @ @ 1
Color ?ello$ ?ello$ "ed 9
8as yes yes Ao 9
Bacteria ty'e Fermentati%e Fermentati%e +*idati%e 9
icture
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Conclusion
hen a ban# of urham tubes containing %arioussugars are used, it
could be 'ossible todetermine $hat sugars an organism is able
toferment yielding a gas and5or an acid
The 'resence of an acid is detectable $ith thecolor change
of a '; indicator in the medium
This indicator is red $hen the '; is abo%e > andyello$
belo$ this 'oint
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.ab "e'ort
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han .ou
