Question

and to assist in maintaining and improving the environment. 4.1 Discuss the uses and advantages of continuous culture in an industrial setting. 4.2 Discuss in detail two major products of industrial microbiology

Answer 1

ANS 4.1 : Continuous culture is an industrial process of maintaining absolutely constant growth rate of culture and its physiological conditions are also maintained constant. It is a fermentation process which is carried out in cstf i.e . continuous stirred tank fermentors. Following are the uses and advantages of continuous cultures:

1.In continuous culture microbial population can be maintained in the logarithmic phase of growth in a constant environment as is desirable in commercial processes.

2. Growth rate of a culture can be maintained absolutely constant.

3.Physiological conditions of the culture can be maintained absolutely constant.

4. In continuous culture , the level of growth can be controlled by maintaining a fixed limiting nutrient concentration.

5. The effluent of continuous culture can be passed either through a centrifuge or a sedimentation tank. thus a concentrated microbial suspension can be produced for recycling to the fermentor.

6. In this type of culture , the autocatalytic nature of microbiological provides an additional significance( i.e. presence of one of the products , additional microorganisms enhances the overall reaction rate.

Thus continuous culture is vastly used commercially .This is is mostly because as compared to batch culture where the productivity is maximum only towards the end of the process, for continuous culture operating at optimum dilution rate under steady state conditions, the productivity will be constant and always maximum.

Moreover since continuous culture is operated for longer period of time ,the negative contribution of the unproductive time (i.e the time taken prior to the establishment of steady state and includes vessel preparation, sterilisation etc.) , to productivity will be minimal.

Thus broadly speaking the process of automation is easier in continuous culture.

ANS 4.2: Following are the two major products of industrial microbiology:

1. Enzymes: mostly employed in :

laboratory

clinical and

industrial.

Protease:

-it is a complex mixture of true proteinases and peptidases.

-alpha amylase a type of protease is produced by bacteria:

Bacillus subtilis and B. licheniformis

and by fungi:

Aspergillus niger and Aspergillus oryzae.

During their production they tend to loose their activity during dehydration so its essential to be careful.

Two types of proteases are their:

A. Alkaline serine protease and B. Acid proteases.

Alkaline serine protease:

These are prodused using bacterium (Bacillus licheniformis)

Subtilisin Carlsberg- most widely used detergent protease.

submerged culture method is used for its production.

Media:

Starch hydrolysate : 50 g/ litre

Soyabean meal: 20 g/litre

Casein: 20g/litre

Na₂HPO₄: 3.3g/litre

Temperature: 30- 40 degree

pH: 7

Enzyme production begins: 10-20 hrs after initiation of cell growth(When maximum cell growth is reached.)

At the end of the productive fermentation, protease is only the protein present in the production medium. This is because all the other proteins are hydrolysed by protease .

YIELD: 10 % of initial protein content of the medium.

Marketed enzyme is as dust free granules containing 1-5 % of enzyme protein.

The enzyme remains stable in liquid preparations (with about 2% of the enzyme).

2.Antibiotics:

STREPTOMYCIN:

Culture used for production: Streptomyces griseus

Substrates: Glucose , fructose, galactose, xylose, mannitol , maltose lactose or starch.

Glucose -one of the best carbon sources.

Fats ,oils and fatty acids may also be used.

Nitrogen source: peptone meat extract soy extract, residues from alcohol distillation and dried Penicillium mycelium , ammonium salts , nitrates and Glycine

Proline is used instead of glutamate because it gives slow growth and a high streptomycine production.

Antioxidants and other growth stimulating substances are added when necessary.

The three phases of fermentation are as follows:

Mycelial growth: pH rises to 8 due to ammonia production. O₂, N, P, Glucose  required.(2 days)

Streptomycin production: no new mycelium formed.

pH falls to 7.0 glucose and oxygen required in large quantities.(1-2 days)

Third phase: autolysis of mycelium: pH value rises continues streptomycin production , pH falls again, Reduction in oxygen requirement.

TOTAL TIME: 5 days.