42. What is the definition of the Decimal Reduction Time (D-value)? How is the D

Question

42. What is the definition of the Decimal Reduction Time (D-value)? How is the D-value often used in the food industry? (2 pts) 43. Answer any two of the following three: [42(a); 42(b); 42(c)). (4 pts) (a) Consider a culture medium which contains the following: glucose; yeast extract; hydrolyszed casein; minerals; water. Which one of these ingredients serves as both a source of vitamins and growth factors? (b) List the two enzymes that have been proposed as missing in bacteria that are incapable of living in the presence of molecular oxygen? 2. (c) If a disinfectant achieves a 90% kill of a microbial population in 1 minute, what is the minimum amount of time (whole minutes) required to achieve a 100% kill of 100,000 microbial cells in a test solution? 44. Imagine that you have discovered a new bacterium. After analysis, the new organism is olerant, thermophilic, acidophilic, autotroph'. Explain, using described as a halot specifie values, to a non-biologist what this means. (2pts)

Explanation / Answer

D - Valve is the time required at a given condition (s) to kill 90% of the exposed organisms. D - value is used in food industry to measure the disinfectants efficiency to reduce the number of microorganisms in the particular food.

43 a) Yeast extract serves as a souce of growth factors and vitamins in nutrient media.

b) Catalase and superoxide dismutase

44) Halotolerent - adaption of microorganisms to high salt conditions.

Thermophillic - presence of microorganisms in high temperatures.

Acidophillic - thriving of microbes at high acidic condition or ph below 3

Autotroph - organisms that are able to form organic substances from inorganic substances like carbondioxide.

37) Cardinal growth temperatures used in microbiology are

minimum ,maximum and optimal temperatures

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