Pseudomonas putida is employed for the bioremediation of petroleum‑contaminated soil. Describe, in detail, (i) the metabolic pathway it uses to degrade alkanes, (ii) the enzymes involved, and (iii) the environmental factors that influence the efficiency of this biodegradation.
Answer
The degradation is aerobic via alkane monooxygenase leading to fatty acids, β‑oxidation, requiring oxygen, moisture, 20–30 °C, and nitrate.
Step-by-step solution
- Alkanes are first activated by alkane monooxygenase, a cytochrome P450 system, introducing a hydroxyl group to form an alcohol.
- The alcohol is oxidised by alcohol dehydrogenase to a fatty acid.
- The fatty acid undergoes β‑oxidation in the peroxisomal pathway, producing acetyl‑CoA which enters the TCA cycle.
- Enzymes: alkane hydroxylase (monooxygenase), alcohol dehydrogenase, aldehyde dehydrogenase, and β‑oxidation enzymes.
- Environmental factors:
- • Oxygen availability – aerobic metabolism is essential.
- • Moisture content – too dry or too wet soil hampers activity.
- • Temperature – optimum between 20 °C and 30 °C for enzyme kinetics.
- • Presence of nitrate or other electron acceptors can enhance degradation rate.
- Concluding that efficient bioremediation requires these conditions.
Common mistake: Confusing aerobic with anaerobic alkane degradation pathways
Concept tested: Bioremediation of hydrocarbons by Pseudomonas
Published · How this solution was prepared and checked
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