Industrial Microbiology (Questions and Answers) | Microbiology

Everything you need to know about industrial microbiology. Some of the most frequently asked questions are as follows:-

Q.1. What is industrial microbiology?

Ans: The use of microorganisms for manufacture of industrial products is known as industrial microbiology.

Q.2. What is a bioreactor?

Ans: Vessels used for industrial fermentation are called bioreactors. These are designed for proper aeration with pH control and temperature control.

Q.3. What is the purpose of a series of impeller paddles and stationary wall baffles in a continuously stirred type bioreactor?

Ans: To keep microbial suspension agitated.

Q.4. Why is there a diffuser at the bottom of the bioreactor?

Ans: For molecular break up of incoming air for maximum aeration.

Q.5. Give one example each of a primary metabolite and a secondary metabolite.

Ans: Ethanol and penicillin.

Q.6. Give two characteristics of primary metabolites.

Ans: (i) Primary metabolites are produced almost at the same time as the cells.

(ii) The production curve of primary metabolites follows the curve for population of cells in parallel with only minimal lag phase.

Q.7. Give two characteristics of secondary metabolites.

Ans: (i) A secondary metabolite is not formed until the microbe has completed its growth phase also known as trophophase, and has attained the stationary phase of growth. The following period in which most of the metabolite is produced is called idiophase.

(ii) Secondary metabolites may be a microbial conversion of a primary metabolite or may be a product of metabolism of the original growth that a microbe produces only after a large number of cells and the primary metabolite have accumulated.

Q.8. What was the ratio of yield of a new strain of Penicillium isolated from cantaloupe from a Peoria, Illinois, supermarket, and then treated with X-rays and nitrogen mustard which is a chemical mutagen in comparison to the original culture of Penicillium notatum?

Ans: More than 100 times, and improvement in fermentation techniques have nearly tripled even this yield.

Q.9. Name a surface on which the microbial cells are immobilized or anchored to make products like high fructose syrups, aspartic acid and some other products of biotechnology.

Ans: Silk fibres or other microscopic spheres or fibres.

Q.10. Which are the common amino acids which are major industrial products of microorganisms?

Ans: Lysine, glutamic acid, phenylalanine and aspartic acid.

Q.11. Which are the amino acids usually produced by Corynebacterium glutamicum?

Ans: Threonine and lysine.

Q.12. Which is the type of mutant used for the maximum production of lysine?

Ans: A mutant of bacterium Corynebacterium glutamicum which lacks the enzymes required to produce threonine is used to make lysine on large scale. This mutant is better in comparison to normal bacterium for the prevention of feedback inhibition as both amino acids require a common enzyme in their synthetic pathway.

Q.13. How is glutamic acid produced from the same bacterium that produces glycine?

Ans: The bacterium is induced to produce glutamic acid by feeding it the minimal amount of the vitamin biotin. Consequently the plasma membrane of the bacterium gets weakened and the glutamic acid leaks into the medium.

Q.14. What is the other product for which this technique of inducing the leaky membrane is exploited?

Ans: Production of antibiotics.

Q.15. What are the uses of citric acid?

Ans: It is an antioxidant and pH adjuster in many foods. In dairy products it is used as an emulsifier. Citric acid is also used in industry and pharmaceutical products.

Q.16. How is a major part of citric acid produced commercially?

Ans: It is produced by mould Aspergillus Niger using molasses as a substrate. This fungus secretes citric acid when given only a limited supply of iron and manganese.

Q.17. Give some common applications of enzymes.

Ans: The amylases are used in the production of syrups from corn starch. Glucose isomerase can turn the glucose formed by amylase from starch into fructose which is used in place of sucrose to sweeten many foods. The enzyme proteases adjusts the amount of glutens (that is protein) in wheat. The other proteolytic enzymes are employed as meat tenderizers or in detergents to remove the proteinaceous stains. The rennin produced from fungi is used to form curd from milk.

Q.18. Which microorganisms are used for the production of vitamin B₁₂?

Ans: Pseudomonas and Propionibacterium spp. As cobalt is a component of B₁₂ cobalt chloride is added to the medium.

Q.19. Which is the organism used to produce riboflavin?

Ans: Ashbya gossypii, a fungus is used in fermentation to produce vitamin riboflavin.

Q.20. How are antibiotics produced?

Ans: The growth medium is inoculated with spores of appropriate mould or streptomycete and is aerated vigorously. After the antibiotic reaches a satisfactory concentration it is extracted from the solution by precipitation and other industrial procedures.

Q.21. What is beer? How is it prepared?

Ans: Beer is made using bottom yeast Saccharomyces carlsbergensis. The germinated barley releases starches and amylase enzymes which is called malting. The enzymes in malt Hydrolyze starch to fermentable sugars called mashing. A liquid called worth is sterilized. The flowers of Hops are added for flavour. Yeast is then added and incubated from 37° – 49°C. In the presence of yeast sugar gets converted into alcohol and CO₂. The alcohol is 4 per cent. The yeast grows on the bottom of the fermenting vessel.

Q.22. What is ale?

Ans: It is prepared like beer and is incubated at 50°-70°C. The microorganism’s top yeast S. cerevisiae converts sugar into alcohol. The alcohol content is 6 per cent and the yeast grows at the top of the fermentation vessel.

Q.23. What is sake?

Ans: The starch of steamed rice is converted into sugar by the fungus Aspergillus oryzae. Yeast is added and incubated at 20°C. The yeast converts sugar into alcohol which is 14 -16 per cent.

Q.24. What is the raw material and which is the organism used to make wine?

Ans: Wine is prepared from grapes using S. cerevisiae and contains 14% or less alcohol. To prepare wine, grapes are crushed into must, SO₂ is added to inhibit wild yeast and then yeast is added to it.

Q.25. What is red wine?

Ans: For red wine black grapes are used and pressing does not occur until after fermentation. It is prepared like natural wine incubated at 25°C. Aged in Oak for 3-5 years and in bottle for 5-15 years.

Q.26. What is white wine?

Ans: It is almost white to colourless or pale yellow. For white wine white grapes (with green, golden or yellow colour skin) are used, the juice being extracted from the pulp by pressing before fermentation. White wine is incubated at 10 – 15°C and aged for 2-3 years in bottles.

Q.27. What is sherry?

Ans: It is like natural wine with additional surface growth floor at 27°C. The alcohol content is 18- 21%. The microorganisms used are S. cerevisiae, S. beticus and S. bayanus. It is S. beticus that grows on the surface as a film producing aldehydes from alcohol.

Q.28. What is sparkling wine (champagne)?

Ans: It is like natural wine using yeast S. cervisiae with secondary fermentation in a bottle. 2.5% sugar and yeast are added to bottled wine. Incubated at 15°C and the botrie is inverted to collect the yeast in the neck of the bottle. In secondary fermentation yeast produces CO₂ and yeast settles quickly.

Q.29. What is rum or Jamaica?

Ans: It is prepared from cane molasses, inoculated from previous fermentations. Wild yeast is used for the purpose. Oak aging adds colour and is finally distilled to concentrate. Alcohol content is 50-95 per cent.

Q.30. What is brandy?

Ans: Fruits are crushed and added to S. cerevisae and distilled for concentration. It contains 40-43 per cent alcohol.

Q.31. What is whiskey?

Ans: Wort is fermented by yeast S. cerevisae. It is distilled to concentrate alcohol and aged in charred Oak barrels. Alcohol content ranges from 50-95 per cent.

Q.32. Give the basic steps in making red wine.

Ans: (1) Grapes are tested and picked.

(2) Crushed and de-stemmed.

(3) Addition of sulphide to kill undesirable microorganisms.

(4) Addition of innoculum (yeast).

(5) Fermentation is carried out.

(6) The resultant is pressed to separate solids from wine.

(7) Wine is clarified in settling vats.

(8) Filtration of wine.

(9) Wine is aged.

(10). Bottling of wine.