Question

Fermentation Test – if we sketch the fermentation tube, what are the expected results?

Hydrolysis of di- and polysaccharides – can disaccharides and polysaccharides undergo hydrolysis? (YES!!) How did the tests you conducted support your answer?

Answer 1

1)

1. Acid production: Changes the medium into yellow color- organism ferments the given carbohydrate and produce organic acids there by reducing the ph of the medium into acidic.
2. Acid and Gas production: Changes the medium into yellow color-organism ferments the given Carbohydrate and produce organic acids and gas. Gas production can be etected by the presence of small bubbles in the inverted durham tubes.
3. Absence of fermentation: The broth retains the red color. The organism cannot utilize the carbohydrate but the organism continues to grow in the medium using other energy sources in the medium.

Yes disaccarides and polysaccarides can undergo hydrolysis reactions

Disaccharides and polysaccharides can be hydrolyzed in the presence of acid or
specific enzymes. When a disaccharide is hydrolyzed, the products are the individual
monosaccharides. When a polysaccharide is hydrolyzed, the products will depend on how
long the mixture is allowed to react, the concentration of acid or enzyme, and other
factors. Polysaccharides are very long and have many glycosidic bonds to hydrolyze.
They cannot all be hydrolyzed at the same time, so the product is a mixture of dextrins,
maltose, and glucose. If a polysaccharide sample is hydrolyzed completely (which means
that it must react for a while), the product is glucose. In this experiment, you will
hydrolyze a sample of sucrose and then test it for the presence of a reducing sugar. You
will also hydrolyze a sample of starch and then test it for the presence of both a reducing
sugar and starch.

Test for Hydrolysis of Sucrose

Hydrolysis of Sucrose
7. Add 0.5 mL of 3 M HCl to 5 mL of a 1 % sucrose solution in a test tube. Mix.
Heat and stir the mixture in a boiling water bath for 20 minutes. (You may add
deionized water to this solution if the volume starts getting low!) Cool the
solution, and add 1 M NaOH until the solution tests neutral on litmus paper. (To
test the solution, you will need both red and blue litmus paper. Add a drop of
NaOH to the solution, stir it with a stirring rod, and then touch the stirring rod to
each piece of litmus paper. Repeat this until neither piece of litmus paper changes
color. A basic solution will turn the red litmus paper blue, and an acidic solution
will turn blue litmus red. If the solution is neutral, neither piece of litmus paper
will change color.)
8. Transfer 8-10 drops of this solution to a small test tube. In a separate tube, mix
together 1 mL of Fehling’s solution A with 1 mL of Fehling’s solution B. Add
this mixture to the small test tube containing your hydrolyzed sucrose, and heat
for a few minutes in a boiling water bath. Record your observations. Compare the
results of this test with your results for unhydrolyzed sucrose in step 1 of this
experiment.

Test fo hydrolysis of Starch

Hydrolysis of Starch
9. Place 3 mL of 1 % starch in a test tube and add 0.5 mL of 3 M HCl. Mix and
place this mixture in a boiling water bath for 10 minutes. After 10 minutes,
remove the tube from the water bath and let it cool. Neutralize this solution with 1
M NaOH and mix well (use the same procedure for neutralization that you used in
step 7 above).
10. Transfer 8-10 drops of this solution to a small test tube. (Save the rest of it for
step 11.) In a separate tube, mix together 1 mL of Fehling’s solution A with 1 mL
of Fehling’s solution B. Add this mixture to the small test tube containing your
hydrolyzed starch, and heat for a few minutes in a boiling water bath. Record your
observations. Compare the results of this test with your results for unhydrolyzed
starch in step 1 of this experiment.
11. Using your solution from the end of step 9 (the hydrolyzed starch solution),
transfer 1 mL to a small test tube. Add 3 drops of the iodine solution, and record
your observations. Compare your results for this test with you results for
unhydrolyzed starch in step 4 of this experiment.

Hope you got the answer