Question

describe the required type of microorganism/s and their role for an effective removal of
petroleum hydrocarbon spill from oil-contaminated soil desert?

Answer 1

There are various groups of microorganisms which can degrade the petroleum hydrocarbon components and therefore can be utilised for remediation of oil contaminated soil desert. Most of the petroleum hydrocarbons in the environment are eventually degraded by indigenous bacteria because of their carbon and energy needs for growth and reproduction, and to relieve the physiological stress caused by the presence of petroleum hydrocarbon components. There are approximately more than 80 genera of microorganisms which have been identified to degrade petroleum hydrocarbons. However, the degradation pathway utilised by a bacteria may vary depending upon the variety of petroleum hydrocarbons which will act as the substrate and specific oxygenase used by a particular bacterial species as the pathway involves oxidizing reactions. For example, some bacteria can break specific alkanes, whereas some will act on the aromatic or resin fractions of hydrocarbons. Some petroleum hydrocarbon degrading bacteria along with their substrates have been listed in the table below:

S.No.	Microrganism	Petroleum hydrocarbon component	Specific degradation profile
1	Pseudomonas sp.	Aliphatics	n-alkanes (C14-C30)
2	Geobacillus thermodenitrifican	Aliphatics	n-alkanes (C15-C36)
3	Rhodococcus sp.	Aliphatics	Cyclohexane, n-alkane(C13-C17)
4	Pseudomonas aeruginosa	Aromatics	Monoaromatics
5	Bacillus sp.	Aromatics	Polyaromatics
6	Mycobacterium cosmeticum	Aromatics	Monoaromatics
7	Pseudomonas sp.	Resins and asphaltenes	Resins and asphaltenes
8	Enterobacter sp., Staphylococcus sp., Bacillus sp.	Resins and asphaltenes	Asphaltenes

The harmful effects posed by oil pollution causes to the environment are well known. For example, the Deep Water Horizon oil spill accident in the Gulf of Mexico, Penglai 19-3 oil spill accident in China have some serious consequences on economy as well as on the residents health. Therefore, degradation of these petroleum components is a matter of major concern. Using bacteria to deal with such environmental pollutants has emerged as a promising strategy because of its low cost and eco-friendly nature.

However, there are many factors which restrict the use of bacteria for the degradation of petroleum hydrocarbons such as:

1. Bioavailability of petroleum hydrocarbons

2. Environmental constraints

3. Metabolic restriction

4. Toxic effect of these substrates on bacteria

5. Long remediation periods