Aim
To
determine the specific carbohydrate fermentation profiles of different
bacteria.
Principle:
Microorganisms
metabolize carbohydrates in various ways. Fermentation is an anaerobic process
where microbes break down carbohydrates, typically producing acid and/or gas as
byproducts. The carbohydrate fermentation test detects acid production as indicated
by a change in the pH indicator (e.g., phenol red) in the medium from its
initial red/orange colour to yellow. Gas production is indicated by the
presence of gas bubbles collected in an inverted Durham tube placed inside the
fermentation broth.
Materials
Required
Bacterial cultures such as Staphylococcus aureus, Escherichia coli, Pseudomonas
and Bacillus,
Basal fermentation broth
containing carbohydrates such as Glucose,
Sucrose, Maltose and Lactose, other routine microbiological facilities.
Procedure
Procedure
1. Basal fermentation broth containing
carbohydrates such as glucose, sucrose, maltose and lactose
were prepared
2. The broth was
dispensed into test tubes with Durham’s tube and sterilized.
3. Using a sterile inoculating loop, each labelled fermentation tube (glucose, sucrose, maltose and lactose) was aseptically inoculated with a small amount of the specific bacterial culture. A negative control was set up for each sugar without bacterial inoculation
4. All inoculated tubes were incubated at 37°C for 24 - 48 hours.
Observation and result
Acid production is indicated if the medium turns
yellow (from red/orange) and Gas production is indicated if bubbles are visible
in the inverted Durham tube.
|
Staphylococcus
aureus |
Escherichia
coli |
Pseudomonas |
Bacillus |
Glucose |
|
|
|
|
Sucrose |
|
|
|
|
Maltose |
|
|
|
|
Lactose |
|
|
|
|
AG = acid and gas (broth turned yellow + bubble trapped in Durham tube)
Composition of
Carbohydrate Broth
Peptone- 10.00 gm
Beef extract- 1.00 gm
Sodium Chloride- 5.00 gm
Glucose/Sucrose/Maltose/Lactose - 10 gm
Phenol Red- 0.018 gm
Distilled water – 1000 ml
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