5 Jan 2012

ISOLATION OF MICROORGANISMS WITH LIPOLYTIC ACTIVITY FROM DAIRY PRODUCTS


RESULTS AND DISCUSSIONS

RESULTS:
BIOCHEMICAL CHARACTERISTICS :
S.NO
Characteristics
Sample -1
Sample-2
Positive
Negative
1
Motility
+
_
NA
NA
2
Gram stain
Gram-Positive rods
Gram
Positive rods
NA
NA
3
Growth onButter Fat   Agar
Small,Creamy white   round  ,  discrete colonies

Small,Creamy white   round  ,  discrete
colonies
NA
NA
4
Catalase
Bacillus
Lactobacillus
Sample -1
Sample -2
5
Oxidase
Bacillus
Lactobacillus
Sample-1
Sample-2
6
Indole
Bacillus
Lactobacillus
------
Sample-1
Sample-2
7
Methyl Red
Bacillus
Lactobacillus
Sample-1
Sample-2
---------------
8
Voges Proskauer
Bacillus
Lactobacillus
Sample- 1
Sample-2
---------------
9
Citrate
Bacillus
Lactobacillus
Sample-1
Sample-2
10
Urease
Bacillus
Lactobacillus
Sample-1
Sample-2
1
Glucose
Bacillus
Lactobacillus
Sample-1
Sample-2

2
Galactose
Bacillus
Lactobacillus
Sample-1
Sample-2

3
Xylose
Bacillus
Lactobacillus
Sample-1
Sample-2

4
Sucrose
Bacillus
Lactobacillus
Sample-1
Sample-2




DISCUSSION:
Pathogenic organisms of both bovine and human origin have­ been isolated from milk. Milk, therefore, can serve as a carrier of diseases. Many serious epidemics were caused by the consumption of such products before this fact was clearly recognized.  However, this became less common as milk sanitation has improved and pasteurization is being more widely practised.
The disease organisms present in milk may be derived from (1) diseased animals or (2) persons collecting and handling milk: Thus the danger is due to the inoculum and not to the growth of organisms in the milk.
            The health of animal is an important factor. Several diseases of cattle including staphylococcal and streptococcal infections, tuberculosis, brucellosis, Salmonellosis, Q fever and Foot and mouth disease may be transmitted to man.
The organisms causing these diseases may get into the milk either directly from the udder, or indirectly from infected body discharges, which may drop, splash, or be blown into the milk.  Some of the important diseases of human origin that have been transmitted by milk are
(1) typhoid fever (2) diphtheria, (3) scarlet fever, (4) dysentery (5) septic sore throat and
(6) poliomyelitis.
           It is also possible for humans to infect animals. For example, mastitis may be caused by a variety of organisms, including Staphylococcus aureus. The infecting organism, in some cases, has been traced to humans.The organisms exist in milk as dormant spores which, unless the milk is subjected to the action of certain physical and chemical stimuli such as heat, cold, or the action of alkalis, remain un germinated.

MILK FERMENTATION:

Raw milk produced under normal conditions develops acidity. It has long been recognised that highly acid milk does not putrefy. Therefore, allowing milk to develop acidity naturally preserves the other milk constituents.  Bacteria in milk are responsible for acid development. They produce acid by the anaerobic breakdown of milk carbohydrate-lactose-to lactic acid and other organic acids. Anaerobic breakdown of carbohydrate to organic acids or alcohols is called fermentation.A number of sugar fermentations are recognized in milk. They can be either homofermentative, with one end product, or heterofermentative, with more than one end product.


1. Streptococci and Lactobacilli., 2. Propionibacteria. , 3. Yeasts - Candida and Torula.  4. Coliform bacteria. Are the organisms responsible for fermentation.
The lactic acid fermentation is the most important one in milk and is central to many processes.  Propionic fermentation is a mixed-acid fermentation and is used in the manufacture of Swiss cheese varieties. Alcohol fermentation can be used to prepare certain fermented milks and also to make ethyl alcohol from whey.
The coliform gassy fermentation is an example of a spoilage fermentation. Large numbers of coliform bacteria in milk indicates poor hygiene. The coliform gassy fermentation disrupts lactic acid fermentation, and also causes spoilage in cheese.
The factors that affect microbial growth also affect milk fermentation. Fermentation rates will generally parallel the microbial growth curve up to the stationary phase. The type of fermentation obtained will depend on the numbers and types of bacteria in the milk, storage temperature and the presence or absence of inhibitory substances.
The desired fermentations can be obtained by temperature manipulation or by adding a selected culture of micro-organisms-starter-to pasteurised or sterilised milk. In smallholder milk processing, traces of milk from previous batches are often used to provide `starter' for subsequent batches. Other sources include the container and additives such as cereal grains.
The fermentation will be established once the organisms dominate the medium and will continue until either the substrate is depleted or the end product accumulates. In milk, accumulation of end product usually arrests the fermentation. For example, accumulation of lactic acid reduces milk pH to below 4.5, which inhibits the growth of most micro-organisms, including lactic-acid producers. The fermentation then slows and finally stops.



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