15. The mean extracellular cellulase activity of 7 Bacillus strains isolated from soil was determined to be 12
IU/mL. A new hyper-producing Bacillus isolate was found to have an extracellular activity of 36 IU/mL. If
equal volumes of the supernatants of all 8 strains are mixed together, the cellulase activity of the solution
will be:
1. 13.5
2. 15
3. 16.5
4. 17.5

Calculating the Combined Cellulase Activity of Bacillus Strains

In this problem, we are given the mean extracellular cellulase activity of 7 Bacillus strains and the activity of a new hyper-producing Bacillus strain. We are asked to determine the cellulase activity of the solution when equal volumes of the supernatants of all 8 strains are mixed together.

Step-by-Step Solution:

1. Mean Cellulase Activity of 7 Bacillus Strains:

   • The mean extracellular cellulase activity of the 7 Bacillus strains is 12 IU/mL.

2. Activity of the New Hyper-Producing Bacillus Strain:

   • The new hyper-producing Bacillus strain has an extracellular cellulase activity of 36 IU/mL.

3. Calculate the Combined Activity of All 8 Strains:

   • We are mixing equal volumes of the supernatants from all 8 strains.

   • The combined cellulase activity is the average of the individual activities of the 8 strains.

   The total activity of the 7 strains is:

   $$7\times 12=84\text{ IU/mL}$$

   Adding the activity of the new strain:

   $$84+36=120\text{ IU/mL}$$

4. Calculate the Average Activity:

   • Since we are mixing equal volumes, the average cellulase activity will be:

   120 IU/mL8=15 IU/mL\frac{120 \text{ IU/mL}}{8} = 15 \text{ IU/mL}8120 IU/mL​=15 IU/mL

✅ Correct Answer:

(2) 15

Conclusion:

The cellulase activity of the solution after mixing equal volumes of the supernatants from all 8 Bacillus strains will be 15 IU/mL. This problem involves calculating the average of multiple values, which is a common technique in experimental setups to determine the overall effect when combining different samples.