What enzymes are involved in yogurt fermentation?

[student101]

What enzymes are involved in the production of yogurt (the fermentation of milk in particular), and what do these enzymes do?

 

[iansmith]

It is not an enzyme that is responsible for te production of yogurt. It is a group of bacteria called the lactic acid bacteria which include the lactococcus and lactobacillus genus.

basically, the lactobacillus will start the yogurt fermentation by converting the lactose (sugar) to lactic acid. the acid produce will drop the pH of the milk therefore changing the chemistry. Due to the pH drop, the protein coagulates and forms what we known as yogurt.

 

[student101]

Yes, but are any enzymes involved at all? Or for that matter, are any enzymes produced or present in yogurt before and/or after production?

 

[iansmith]

The bacteria due produce enzymes that are responsible for transforming lactose to lactic acid and if you did an analysis for the enzymes would might see different enzyme at different time point.

However there is not enzyme present in the milk that would cause the fermentation of yogurt.

 

[student101]

Is that enzyme that the bacteria produce called "lactase"? If so, are there any other enzymes that are produced by the bacteria?

 

[Ouabache]

There is only one enzyme that I am aware of, necessary for yogurt culture and that is β-galactosidase.

Some commonly used bacteria to make yogurt, are: Lactobacillus bulgaricus, Lactobacillus acidophilus & Streptococcus salivarius.

They absorb the lactose across their membrane and catabolize the lactose into two smaller sugars galactose and glucose by producing the enzyme β-galactosidase (synonym for lactase). Their byproduct is lactic acid which passes out of the bacteria, lowers the pH of the medium, which as iansmith also mentioned, coagulates the milk protein into a curd just like cheese and tofu.

So there are no additional enzymes found in the milk or yogurt. All the biochemistry is internal to the bacteria. The bacteria will catabolize the galactose and glucose using enzymes. But you can find out what those are in the library, in any introductory biochemistry book.

 

[student101]

These other enzymes...is there anywhere on the net where I can further research them? (I'm kinda tight on time and space, so going to a library/textbook isn't really an option right now)

 

[KMCB1234]

But you can find out what those are in the library, in any introductory biochemistry book.

What books ? what titles are they ?

 

[KMCB1234]

Well , I want to make yogurt to eat only
after reading your scientific posts

 

[Ouabache]

What books ? what titles are they ?

A couple that come to mind are:

Lehninger Principles of Biochemistry
by Albert L. Lehninger, David L. Nelson, Michael M. Cox
ISBN: 0716743396

and

Biochemistry
by Lubert Stryer, John L. Tymoczko, Jeremy Mark Berg
ISBN:0716730510

makes for some great late night reading