5. (10 points, total) A startup company is evaluating the potential of producing
ID: 72340 • Letter: 5
Question
5. (10 points, total) A startup company is evaluating the potential of producing single cell protein (SCP) using microalgae. The volume of the designed bioreactor is 1000 L and the desired production rate is 90 g protein/month. They are screening two microalgae strains: A and B. The characteristics of these strains are: Strain A: 70% of dry weight is protein Doubling time: 36 hrs Dry weight of single cell: 3 × 10-10 g
Strain B: 60% of dry weight is protein Doubling time: 24 hrs Dry weight of single cell: 3 × 10-10 g
Which of these two strains will meet the desired production rate assuming the initial cell concentration of 1 million cells/L? Clearly show all your calculations and assumptions.
Explanation / Answer
Strain A:
70% dry weight is protein. Dry weight of single cell = 3 x 10-10gm
Protein in dry weight = 0.7 x 3 x 10-10gm = 2.1 x 10-10gm protein / cell.
Total amount of protein required = 90 gm
No. of cells required to produce 90 gm proteins = 90/2.1 x 10-10 = 43 x 1010 or 4.3 x 1011 cells.
Initial cell concentration = 106 cells/ltr.
Therefore, in 1000L, the no. of cells will be 109 cells.
Doubling time = 36 hrs
Nt = No. 2n
4.3 x 1011 cells = 109 x 2n
n = 8.75 generations
Time required for 1 generation = 36 hrs
Time required for 8.75 generations = 315 hrs = 13.125 days.
Strain B:
60% dry weight is protein. Dry weight of single cell = 3 x 10-10gm
Protein in dry weight = 0.6 x 3 x 10-10gm = 1.8 x 10-10gm protein / cell.
Total amount of protein required = 90 gm
No. of cells required to produce 90 gm proteins = 90/1.8 x 10-10 = 50 x 1010 or 5 x 1011 cells.
Initial cell concentration = 106 cells/ltr.
Therefore, in 1000L, the no. of cells will be 109 cells.
Doubling time = 24 hrs
Nt = No. 2n
5 x 1011 cells = 109 x 2n
n = 8.5 generations
Time required for 1 generation = 24 hrs
Time required for 8.5 generations = 204 hrs = 8.5 days.
Therefore, both the strains will reach the desired production rate. However, strain B will reach earlier than strain A.
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