The acidity of food is generally expressed in terms of pH value and it has great influence on distribution of microorganism. Lower the pH, greater the ease of processing or sterilization. On the basis of acidity, food can be classified as follows, Read more
Yeast are group of non-mycelial unicellular fungi belonging to the group Ascomycetes. They are cosmopolitian fungi which occur in almost all places of the world having organic matter, especially sugars. Most of the species are saprophytes. They grow on the nectar of flowers, surface of sweet fruits, sugarcane, milk and other food stuffs, animal excreta, humus of soil etc.
In general, yeast cells are longer than most bacteria. Yeast vary considerably in size ranging from one to five μm in width and from 5 to 30 μm or more in length. They are commonly egg shaped but are sometimes lemon shaped, pear shaped or elongated into false or true mycelium. Yeast have no flagella and other organelles of locomotion. Read more
The bacterial structures internal to cell wall includes cytoplasmic membrane, protoplast, spheroplast, spores, plasmid and others.
Cytoplasmic membrane: This is a thin structure that completely surrounds the cell. Its size is approximately 7.5 nm in thickness and is composed primarily of phospholipid (20 – 30 %), protein (60 – 70 %). The phospholipid form bilayered structure in which most of the protein are embedded tightly called integral protein. This protein can only be removed by destruction of the membrane with treatment such as with detergent. Other protein which are loosely attached are called peripheral protein. This peripheral protein can be easily removed mild treatment such as osmotic shock. Read more
The morphology of bacterial cell includes characteristics such as size, shape, structure etc. First of all, Leeuwenhoek revealed the gross appearance of microorganism including bacteria by light microscope. By the discovery of electron microscope in early 1940’s the study of structural bacterial cell has been made very easier. The morphological characteristic of a bacterial cell is as follows.
Size: Bacteria vary in size from cell to cell. It can be as small as 0.1 to 0.2 μm in width to as large as more than 50 μm in diameter. A few very large prokaryotes such as Epulopiscium fishelsoni  that inhabits the intestinal tract of Surgeon fish are up to 50 μm in diameter and can be more than 0.5 mm in length. However, the dimension of an average rod cell prokaryotes E.coli are about 1×3 μm. Read more
Microorganism for the production of industrially important products are useful only if they can be maintained indefinitely in healthy, pure and genetically stable form. Industrial culture collection consists of stock culture. Stock culture may be simply defined as a culture which serves as source of inoculum. Stock cultures are of two types.
1. Working stock culture: Working stock culture: This culture is maintained at vigorous and uncontaminated condition. Since this culture is used frequently, it must be routinely checked for characteristic feature and contamination.
2. Primary stock culture: This culture is kept for long term storage and are maintained at low physiological activity condition. The cultures are used to produce new working stock culture as per need. Read more
Microbial protein are commonly called single cell protein (SCP) referring to the fact that most of the microorganism used as protein producers are single cells or filamentous individual. SCP is a generic name which refers to dry cells or protein concentrates from microorganism obtained by growing in large amount in variety of abundant and inexpensive culture media and used as protein supplement for human and animal. SCP should not be confused with biomass (ex; mushroom) and microbial biomass. SCP can be produced using different species of bacteria, yeast or fungi.
Pure culture: A culture that contains only one kind of microorganism is called a pure culture. A culture which contains more than one kind of microorganism is called a mixed culture. A pure culture has only a single type of colony. Pure cultures are essential in order to study colony characteristics, biochemical properties, morphology, staining reaction, immunological reaction or susceptibility towards antimicrobial agents of particular strain of fungus, bacteria or actinomyces. Read more