The Influence of Biosurfactants on the Rate of Oil Spill BioremediationBIOLOGICAL RESEARCH PROJECT

BY EMILY MA

Introduction

Problem: Petroleum oil is a significant source of nonrenewable energy that contributes to sustaining society; however, an oil spill can have disastrous effects on the biodiversity and productivity of a marine ecosystem.

Solution: Bioremediation is an oil spill treatment that uses naturally occurring organisms to break down toxic substances into less hazardous ones. Bacteria play a crucial role in the biodegradation of oil by producing biosurfactants.

Competing Technologies

Other methods that control oil spills include a variety of booms, barriers, and skimmers, as well as natural and synthetic absorbent materials

These methods work by physically removing the oil from the body of water

However, these methods are inefficient because they are not cost-effective, they require high maintenance, and these processes occur at a slow rate

A disastrous oil spill occurring in the Gulf of Mexico, which killed thousands of marine organisms and had lasting effects on the environment

Limiting Factors to Bioremediation

TemperatureLow temperatures can hinder the biodegradation process because molecules move at a slower rate, and the impact of some molecule collisions would not be strong enough to bring about a reaction.

OxygenOxygen is also necessary because it is needed for aerobic hydrocarbon degradation reactions, one of the processes essential for bioremediation.

Nitrogen and PhosphorusIn addition, bacterial metabolism requires certain amounts of nitrogen and phosphorus as sources of nutrients.

Physical Status of an Oil Spill

The distribution of oil in the water spreads throughout the depth of the ocean.

• The lighter potion of the oil normally spreads and forms a thin layer on the top of the body of water

• Most of the oil emulsifies and dissolves in the mid-potion of the water.

• Some denser potions of oil sink to the bottom of the ocean. The release and distribution of oil in the water column due to the differences

in physical status and density of the oil that was released

Oil degrading Bacteria

Types of Bacterial Biosurfactants

Low molecular weight Structure-usually glycolipids, in which

carbohydrates are attached to a long chain of aliphatic acid or lipopeptides

Benefits-efficiently lowers surface and interfacial tension and has a high specificity

Setbacks-Cannot bind tightly the surface molecules and less effective in preventing the combination of oil molecules

High molecular weight Structure-this kind of bacterial

biosurfactant are composed of polysaccharides and other high weight molecules

Benefits-Efficient at coating oil droplets, prevents coalescence of oil, and has a high specificity

Setbacks-less effective at reducing surface tension

Design

Since high molecular weight and low molecular weight biosurfactants essentially do different tasks, creating genetically modified bacteria that would produce both types of biosurfactants would increase the rate of bioremediation.

Producing a bacteria that can synthesize and regulate the production of rhamnolipids (a low molecular weight biosurfactant) and alasan (a high molecular weight biosurfactant) would be a very effective way to treat oil spills

Types of Biosurfactants Used

Alasan This biosurfactant is composed of an

anionic polysaccharide and a protein with a high molecular weight and is covalently bound to alanine, an enzyme

Alanine plays an important role in the structure and function of alasan

Allows this biosurfactant to become more effective in stabilizing oil emulsions and in solubilizing hydrocarbons

Rhamnolipids Rhamnolipids are a class of glycolipid

produced by multiple species of Pseudomonas and it has a low molecular weight

Pseudomonas aeruginosa has the ability to metabolize an array of substrates, including n-alkanes, hexadecane and oils

The rhamnolipids are able to emulsify the oil and lower interfacial, and in turn, increase the rate of uptake in bacteria

This system consists of the following parts

gene that enables the cell to produce rhamnolipids

gene that enables the cell to produce alasan

a sensor that would detect the presence of hydrocarbons in the oil spill (Lacl)

a regulator to transform the signal and activate the promoter (IPTG)

promoter to turn on the gene

open reading frame (Plac) that will ultimately produce alasan

a sensor that would detect the presence of alasan

a regulator to transform the signal and activate another promoter

another promoter to turn on the gene

open reading frame that will produce rhamnolipids

the terminating sequence

Pseudomonas aeruginosa

Under the Presence of Hydrocarbons:

1)The hydrocarbon sensor is stimulated

2)IPTG is activated and it transforms the signal

3)This activates the promoter

4)The Plac gene is turned on and it starts to produce alasan

Hydrocarbon sensor (Lacl)

Presence of hydrocarbons

Regulator (IPTG)

Open reading frame (Plac) on

Alasan is produced

Under the Presence of Alasans:

1)The alasan sensor is stimulated

2)The regulator is activated and it transforms the signal

3)This activates the promoter

4)A certain gene is turned on and it starts to produce rhamnolipids

Alasan sensor

Presence of alasan

Regulator

Open reading frame on

Rhamnolipids are produced

• when there are no hydrocarbons present, then no chemical reaction would take place and neither alasan nor rhamnolipids would be produced

• when there are hydrocarbons present, both alasan and rhamnolipids would be produced.

• when there are no hydrocarbons present and alasan is present, rhamnolipids would be produced

Hydrocarbon

s

Alasan Rhamnolipid

s

0 0 0

1 1 1

0 1 1

Truth Table

Potential Problems

One of the main problems in this design is the possibility of Pseudomonas aeruginosa overpopulating and an algae bloom occurring

In addition, there could be a problem with the design if there is a surplus of alasan and rhamnolipids are continuing to be produced without the presence of oil

Overall there is a low risk factor for this design, and it is a quick and efficient way to speed up the rate of oil spill bioremediation

Conclusion

Biosurfactants are produced by a vast array of oil-degrading microorganisms

These biosurfactants can have a low molecular weight, and decrease the oil-water interfacial tensions, or they can have a high molecular weight, and act as biodispersants by preventing the coalescence of oil droplets in the water

These biosurfactants simulate the growth of oil-degrading bacteria and improve their ability to utilize hydrocarbons

Bibliography

http://www.researchgate.net/publication/6424393_Molecular_and_structural_characterization_of_the_biosurfactant_produced_by_Pseudomonas_aeruginosa_DAUPE_614

http://repository.ias.ac.in/17365/1/409.pdf

http://www.iisc.ernet.in/currsci/jul10/articles19.htm

http://www.sciencedirect.com/science/article/pii/S0960852415006604

http://microbewiki.kenyon.edu/index.php/Oil_spills

http://dujs.dartmouth.edu/winter-2012/oil-spills-severity-and-consequences-to-our-ecosystem#.VZPqbPlViko

https://en.wikipedia.org/wiki/Rhamnolipid

http://parts.igem.org/Part:BBa_K398206

http://www.epa.gov/oem/content/learning/oiltech.htm