Microorganisms and biotechnology

  • Microorganisms are living organisms which are not visible to the naked eye and which can be observed under a microscope.
  • They are also called microbes.
  • They can be unicellular or multi cellular.
  • Microorganisms are found in virtually every habitat or ecosystem, such as the poles, deserts, rocky area.



Viruses are not true living things. They are not considered to be alive,  because on their own they can do nothing until they enter a living cell.  They have the following characteristics.

  • Size: Less than 300nm in size- around 50 times smaller than a bacterium. They can be seen only with an electronic microscope.
  • Genetic material: They contain nucleic acid DNA or RNA
  • Cell wall: They have no cell wall but surrounded by a protein coat known as capsd made up of capsomere.
  • Method of feeding: Parasitic- feeds by living in or on other living organisms harming the host cell
  • Reproduction: Reproduce only inside living (host) cells
  • Food storage: No foods stored
  • Cytoplasm: Absent
  • Cell membrane: Absent
  • Mitochondria: Absent
  • Organization: Non cellular- have no cell contents



Bacteria cells are very different from the cells of all other organisms; they do not have a nucleus. Bacteria are the simplest of the living organism. They have the following characteristics:-

  • Size: They have a size in range of 0.5 – 5 µm. visible from a light microscope
  • Genetic material: They contain nucleic acid DNA which lies ‘loose’ in the cytoplasm
  • Cell wall: Have cell wall made up of murein
  • Method of feeding: May be parasitic or they may be saprophytic- feeding on dead organic matter causing it to decay
  • Reproduction: Binary fission
  • Food storage: In form of glycogen
  • Flagellum: Present in some, used for locomotion
  • Cytoplasm: Present
  • Cell membrane: Present
  • Mitochondria: Absent
  • Organization: Unicellular- made up of one cell



For a very long time fungi were classified as plants.However; they are very different from plants and belong to their own kingdom. Fungi do not have chlorophyll and do not do photosynthesis. They have the following characteristics:-

  • Size: can be seen by the naked eye and visible with a light
  • Nucleus: present
  • Genetic material: nucleic acid DNA
  • Cell wall: made up of chitin
  • Method of feeding: parasitic or they maybe saprophytic
  • Reproduction: by producing spores
  • Hyphae: usually made up of large number of tubular treads called hyphae intertwined to form mycelium
  • Cytoplasm: present
  • Cell membrane: present
  • Mitochondria: present
  • Organization: multicellular

The uses of microorganisms


  • Many microorganisms such as bacteria and fungi feed as saprotrophs, using external digestion.
  • They release enzymes onto the dead matter these enzymes are:-
  1. Amylase which digested starch into simple sugars
  2. Protease which digests proteins into amino acids which are further broken down into ammonium ions.
  3. Lipase which digests fats into fatty acids and glycerol
  • The products formed by their enzyme reactions are absorbed by the microorganisms for use in their metabolism.
  • Gradually the dead matter is broken down, releasing its mineral ions which are returned to the soil for recycling as they are taken up for use by the plants.


Yeast is the microorganism used in bread making but the only fermentation product needed is carbon dioxide.

  • Flour, water, salt and yeast are mixed to make dough.
  • Yeast releases enzymes amylase which digests the starch in the flour into sugar.
  • The yeast uses the sugar for anaerobic respiration to produce carbon dioxide and alcohol.
  • The dough is repeatedly folded and kneaded either by hand or machine.
  • The dough is then left for an hour with an optimum temperature of 27°C while the yeast does its work
  • The accumulating carbon dioxide makes the dough rise to about double of its volume.
  • The dough is then put into a baking tin and into an oven at about 200°C
  • This temperature makes the bubbles to expand more, kills the yeast and evaporates the small amount of alcohol before dough turns into bread.


  • To make wine yeast is added to fruit sugar and to make beer yeast is added to maltose from barley grains.
  • The yeast allowed to ferment the sugar at a controlled temperature in a vessel called fermenter.
  • The optimum temperature for the growth of yeast is 20°C.
  • The yeast converts the sugar to alcohol by anaerobic respiration, with carbon dioxide released as a waste product.
  • As the concentration of alcohol increases, it eventually kills the yeast.
  • The yeast is removed from the liquor by filtration to produce a yeast free alcoholic drink.
  • The drink can be distilled to produce a higher alcoholic drink.



  • First the fat and protein content of the milk is adjusted and the milk is homogenized.
  • Then the milk is pasteurized
  • Species of streptococcus or lacto bacillus are added to the milk and mixed a suitable temperature of 40°C is provided.
  • At this stage a mixture of enzymes called rennet is added. Rennet contains enzyme Chymosin.
  • Chymosin coagulates milk protein casein and forms the semi-solid curds.
  • The jelly like curds is cut up and the remaining liquid called whey is drained off from the curds which are partially dried and compressed to form cheese.



  • First the fat and protein content of the milk is adjusted and the milk is homogenized.
  • Then the milk is pasteurized
  • The pasteurized milk is then fermented by adding starter culture of bacteria.
  • The bacteria act on milk protein called lactose and converts it to lactic acid.
  • Lactic acid coagulates the milk protein called casein to produce the thick creamy consistency of yoghurt.
  • The fermentation works best at a temperature of 46°C and when completed yoghurt is cooled to 5°Cto stop the bacterial process.
  • The lactic acid gives the yoghurt its slightly sour taste.


  • The fermenter is steam sterilized and loaded with culture medium containing:
  • Glucose/lactose- required s a respiratory substrate to release energy during aerobic respiration, for the rapid reproduction and growth of new (penicillium) cells
  • Amino acids- requires nitrogen in order to make protein and other nitrogenous cell components required to make new plasma membranes and protoplasm to produce new fungi cells for healthy growth of the fungi (penicillium)
  • Mineral salts
  • The relevant penicillium strain is inoculated into the culture medium,
  • For optimum growth optimum pH and optimum temperature is provided.
  • The fermenter is continuously stirred and sterile air is blown in through many very small holes for aerobic respiration of penicillium to release energy for rapid growth.
  • Air is blown through small holes to increase surface area of air absorbed by the penicillium cells resulting in an increased rate of respiration.
  • Initially the temperature of the fermentor increases due to the heat energy released by the fungi during respiration.
  • To control the temperature an external cooling jacket is used.
  • Penicillin is a secondary product, produced in large quantities only towards the end of the growth period of the fungus.
  • The broth is then filtered to remove the cells, which are washed to remove any entrapped penicillin. Penicillin passes into filtrate, extracted and crystallized.



  • It is produced by unicellular organisms. The major constituent of cytoplasm of bacteria and fungus is protein.
  • The single cell is produced in a large container called fermenter.
  • The medium such as Molasses, liquid whey etc can be used to grow the fungus.
  • The fermenter and the medium are sterilized to kill other microbes, which may contaminate the products.
  • The starter culture such fungus Fusarium is reactivated and added to the medium. This is called inoculation.
  • The medium must contain glucose as a source of energy, nitrate as a source of nitrogen.
  • Air is admitted into the medium for the aerobic respiration of fungus.
  • The paddles of the fermenter rotate to prevent the clogging of the fungal filament. (pH 6 to 7 and temp 27 to 30oC)
  • Under these condition the fungus multiplies in large scale, which is removed from the fermenter, filtered purified and used as protein rich food material.

                 Uses of fermenters for Single cell protein production

  • Large amount of protein can be produced in a short period of time
  • The food produced by this method is rich in protein, contains less fat and more dietary fiber.
  • Single cell protein is independent of climatic changes.




Penicillin, which remains an important part of our antimicrobial armamentarium, had a significant impact on the second half of the twentieth century. Penicillin is an excretory products produced by fungal cells as the rate of growth slows down.


The following steps are involved in the synthesis of Penicillin.

  • The antibiotic penicillin ids produced in a large container called Fermenter or Bioreactor.
  • The fermenter is filled with nutrient broth (culture medium) such as corn steep liquor.
  • Nutrient broth contains carbohydrate lactose which is used as a source of energy and amino acids to synthesize protein.
  • The fermenter and the medium are sterilized to kill the other microorganisms which may contaminate the food.
  • Other essential mineral ions are added.(pH- 5 to 6, temp- 26 to 30 oC)
  • Sterilized air is pumped into the fermented for the aerobic respiration of fungi.
  • Starter culture Fungus Penicillium strain is added into the medium.
  • The medium is stirred to prevent the clogging of the fungal filaments. Under these conditions the fungus begins to multiply using the nutrients.
  • When the nutrients begin to decrease the fungus starts to produce the antibiotics.
  • When the nutrients are completely used up, the culture medium is taken out, crushed, filtered and the antibiotic penicillin is purified by crystallization.