Litmus is an

oxidation reduction indicator.

Litmus milk now forms an excellent differential medium in which microorganisms can

metabolize milk substrates depending on their enzymatic complement.

______ ____ now forms an excellent differential medium in which microorganisms can metabolize milk substrates depending on their enzymatic complement.

Litmus milk

~LACTOSE FERMENTATION~
Organisms capable of using __a____ as a carbon source for energy production utilize the inducible enzyme __________b__________.

a. lactose
b. ßglalctosidase

~LACTOSE FERMENTATION~
Organisms capable of using lactose as a carbon source for energy production utilize the inducible enzyme ß-galactosidase and degrade lactose as follows:

Lactose → ßgalactosidase→ GLUCOSE+ GALACTOSE
↓Embden-Meyerhof pathway
Pyruvic acid
↓
Lactic acid

~GAS FORMATION~
The end products of microbial fermentation of lactose are likely to include the gases

CO2↑(carbon dioxide)+H2↑(hydrogen peroxide).

~GAS FORMATION~
The presence of gas may be seen as

separations of the curd or by the development of tracks or fissures within the curd AS GAS RISES TO THE SURFACE.

~LITMUS REDUCTION~
_________ is an anaerobic process involving biooxidations that occur in the absence of molecular oxygen.

Fermentation

~LITMUS REDUCTION~
_______ ___ cannot exist in the free state, there
must be an immediate & concomitant electron acceptor available to bind these hydrogen ions, or else oxidation reduction reactions are not possible & cells cannot manufacture energy.

Hydrogen ions

~LITMUS REDUCTION~
In the litmus milk test, _____ acts as such an acceptor.

litmus

While in the oxidized state, the litmus is _____ (what color)

purple

When the litmus accepts hydrogen from a substrate, it will become REDUCED & turn ____ or ____ colored.

white / milk

Definition of oxidized

1. To combine with oxygen; make into an oxide.
2. To increase the positive charge or valence of (an element) by REMOVING electrons

Oxidation of lactose, which produces _____ ___, butyric acid CO2↑ & H2↑ is as follows:
Lactose→Glucose→Pyruvic acid→Lactic acid
→Butyric acid
→CO2 + H2

lactic acid

~CURD FORMATION~
There are 2 distinct types of curds. What are they

1- acid
2-rennet

~CURD FORMATION~
Acid curd

Lactic acid or other organic acids precipitation of milk protein caseinas CALCIUM CASEINATE to form an insoluble clot. THE CLOT IS HARD & WILL NOT RETRACT FROM THE WALL OF THE TEST TUBE.

Acid curds are

hard & will not retract from walls of test tube.

~CURD FORMATION~
Rennet curd

Some organisms produce rennin, an enzyme that acts on casein to form paracasein, which in the presence of calcium ions is converted to calcium paracaseinate & forms an insoluble clot. Unlike acid curd, THIS IS A SOFT SEMISOLID CLOT THAT WILL FLOW SLOWLY WHEN THE TUBE IS TILTED.

Which curd is known to be soft & semisolid and will flow slowly if tube is tilted?

Rennet curd

Which curd is known to be hard and not retract from tube walls?

Acid curd

~Proteolysis (Peptioniztion)~
The inability of some microorganisms to obtain their energy by way of lactose fermentation means they must use other nutritional sources such as ______ for this purpose.

proteins

~Proteolysis (Peptioniztion)~
By means of proteolytic enzymes, these organisms __a___ the milk protein, primarily casein, into their basic building blocks, namely __b_______.

a. hydrolyze
b. amino acids

~Proteolysis (Peptioniztion)~
Hydorlyizng milk proteins into amino acids is accompanied by the evolution of __________________, resulting in alkaline pH in the medium

large quantities of ammonia

~Proteolysis (Peptioniztion)~
Large quantities of ammonia resulting in alkaline pH in the medium turns the litmus to a _________ color in the upper portion of the tube, while the medium begins to lose body & produces a translucent, brown, wheylike appearance as the protein is hydrolyzed to amino acids.

deep purple

~ALKALINE REACTION~
An alkaline reaction is evident when the color of the medium

remains unchanged or changes to a deeper blue.

When the medium remains unchanged or turns deep blue, that reaction is indicative of the

partial degradation of CASEIN into SHORTER POLYPEPTIDE CHAINS.

Litmus milk reactions image

Control= uninoculated
The far right (very last one) is proteolysis