A biotechnology startup is researching the commercial cultivation of the green microalga Chlorella vulgaris in photobioreactors for protein production. They are investigating how varying the nitrate concentration in the culture medium affects both the rate of photosynthesis and the final dry algal biomass.
The table below shows the results of their investigation:
| Nitrate concentration (mg dm−3\text{mg dm}^{-3}mg dm−3) | Rate of photosynthesis (arbitrary units) | Dry algal biomass produced (g dm−3\text{g dm}^{-3}g dm−3) |
|---|---|---|
| 5 | 2.5 | 2.0 |
| 15 | 4.6 | 4.0 |
| 30 | 7.8 | 6.5 |
| 60 | 9.4 | 8.2 |
| 120 | 10.5 | 11.4 |
| 240 | 9.8 | 10.2 |
Explain why there is a direct link between the rate of photosynthesis and the dry biomass produced by the algal culture.
Identify the nitrate concentration that produced the highest dry algal biomass.
Calculate the percentage increase in dry algal biomass when the nitrate concentration is increased from 15 mg dm−315\text{ mg dm}^{-3}15 mg dm−3 to 120 mg dm−3120\text{ mg dm}^{-3}120 mg dm−3.
Suggest why the rate of photosynthesis and the dry biomass produced do not follow a perfectly proportional pattern across all nitrate concentrations.
State three environmental factors, other than nitrate concentration, that the researchers must control to optimize the rate of photosynthesis and microalgal growth.
