Question

The decimal reduction time (DRT or D value) of a bacterial culture is one minute. If a suspension of the bacterial culture contains an initial population of \( 10^6 \) cells, then the time (in minutes) required to reduce the number of bacteria to 10 by heat treatment is ............

Hint:

To calculate the time required to reduce a bacterial population by a certain factor, multiply the DRT by the number of times the population must be reduced by a factor of 10.

Answer 1

Correct Answer: 5

Step 1: Understanding DRT.
The decimal reduction time (DRT) is the time required to reduce the bacterial population by 90%. The population decreases by a factor of 10 for every DRT. If the initial population is \( 10^6 \), and we want to reduce it to 10, we need to reduce it by five orders of magnitude (from \( 10^6 \) to \( 10^1 \)).

Step 2: Calculating the time.
Each DRT reduces the population by a factor of 10. So, to reduce the population from \( 10^6 \) to \( 10^1 \), it takes: \[ 5 \times \text{DRT} = 5 \times 1 \, \text{minute} = 5 \, \text{minutes}. \]

Step 3: Conclusion.
The required time to reduce the bacterial population to 10 is \( \boxed{5} \, \text{minutes} \).