CRUDE OIL DEGRADATION BY MARINE MICROORGANISMS

Marine pollution and microbial remediationISA-IIMI-1414MICROBIOLOGY

introduction Petroleum is a viscous liquid mixture that contains

thousands of compounds mainly consisting of carbon and hydrogen.

Petroleum-based products are the major source of energy for industry and daily life.

Release of hydrocarbons into the environment whether accidentally or due to human activities is a main cause of water and soil pollution.

Soil contamination with hydrocarbons causes extensive damage of local system since accumulation of pollutants in animals and plant tissue may cause death or mutations .

Composition of crude oil Crude oil which is a heterogeneous liquid

consisting of hydrocarbons comprised almost entirely of the elements hydrogen and carbon in the ratio of 2:1

It also contains elements such as nitrogen, sulfur and oxygen, all of which constitute less than 3% (v/v). There are also trace constituents, comprising

less than1% (v/v), including phosphorus and heavy metals such as vanadium and nickel.

crude oil can be classified into four main groups of chemicals:

the saturated hydrocarbons poly aromatic hydrocarbons, polar, non-hydrocarbon components-resins

(pyridines, quinolines,carbazoles, sulfoxides, and amides)and the asphaltenes(phenols, fatty acids, ketones, esters,

and porphyrins). Saturated hydrocarbons constitute the largest

fraction of crude oil Aromatic hydrocarbon and polar fractions are

more toxic and persistant

Microbial degradation of crude oil Biodegradation of petroleum hydrocarbons is a complex

process that depends on the nature and on the amount of the hydrocarbons present.

Hydrocarbons in the environment are biodegraded primarily by bacteria, yeast, and fungi. mixed populations with overall broad enzymatic capacities are required to degrade complex mixtures of hydrocarbons such

as crude oil in soil, fresh water, and marine environments. Bacteria are the most active agents in petroleum

degradation

Bacteria Yeast Fungi Achromobacter Candida Aspergillus Acinetobacter Cryptococcus Cladosporium Alcanivorax Debaryomyces Corollasporium Alcaligenes Hamsenula Cunninghamella Bacillus Pichia Dendryphiella Brevibacterium Rhodotorula Fusarium Burkholderia Saccharomyces Gliocladium Corynebacterium Sporobolomyces Luhworthia Flavobacterium Torulopsis Penicillium Mycobscterium Trichosporon Varicospora Nocardia Yarrowia Verticillium Pseudomonas Rhodococcus Sphingomonas Streptomyces Table 1. Crude-oil degrading microorganisms

Mechanism of degradation The degradation of petroleum hydrocarbons can be mediated

by specific enzyme system -oxygenases, Cytochrome P450 alkane hydroxylases.

attachment of microbial cells to the substrates production of biosurfactants-Surfactants enhance solubilization and removal of contaminants.Biodegradation is also enhanced by surfactants due to increased bioavailability of pollutants. eg:Pseudomonas aeruginosa and Rhodococcus erythropolis.

Biosurfactants increase the oil surface area.

Biosurfactants can act as emulsifying agents by decreasing the surface tension and forming micelles. The microdroplets encapsulated in the hydrophobic microbial cell surface are taken inside and degraded

Thus..

Aerobic degradation

Aerobic degradation of crude oil hydrocarbons with its environmental impact. Biodegradation of n-alkanes: metabolism begins with the activity of a monooxygenase which introduces a hydroxyl group into the aliphatic chain.[A]-monoterminal oxidation, [B]-biterminal oxidation, [C]- subterminal oxidation; TCA

Anaerobic degradation

Remediation The technology commonly used for the soil

remediation- mechanical Burying evaporation dispersion washing However, these technologies are expensive

and can lead to incomplete decomposition of contaminants.

bioremediation The process of bioremediation, defined as the use of

microorganisms to detoxify or remove pollutants owing to their diverse metabolic capabilities.

cheaper than other remediation technologies. strategies: 1.Nutrient enrichment (Biostimulation) eg: Exxon,

and the State of Alaska have carried out extensive nutrient enrichment testing on beaches polluted by oil from the Exxon Valdez, nutrient enrichment in near shore areas off the coast of New Jersey, in Prudhoe Bay, and in several ponds near Barrow, Alaska.

2. Seeding with naturally occurring microorganisms (Bioaugmentation)

3. Seeding with genetically engineered microorganisms (Bioaugmentation with GEMs)

Factors affecting crude oil degradation in marine environment

Oxygen availability Microorganisms employ oxygen-incorporating

enzymes to initiate attack on hydrocarbons. Nutrient availability nitrogen, phosphorus, and iron-rate limiting Eg. by adding nitrogen- and phosphorus-rich fertilizers to stimulate

biodegradation of petroleum hydrocarbons Prince William Sound, Alaska.

Temperature The temperature of most seawater is between –2 and

35⁰C At low temperature, the rate of hydrocarbon

metabolism by microorganisms decreases. lighter fractions of petroleum become less volatile,

thereby leaving the petroleum constituents that are toxic to microbes in the water for a longer time and depressing microbial activity.

Petroleum also becomes more viscous at low temperature.

Other factors-pressure, salinity, and pH.

REFERNCES Dorota Wolicka and Andrzej Borkowski (2012) Microorganisms and

Crude Oil, Introduction to Enhanced Oil Recovery (EOR) Processes and Bioremediation of Oil-Contaminated Sites, Dr. Laura Romero-Zerón (Ed.), ISBN: 978-953-51-0629-6, InTech.

Mehdi Hassanshahian and Simone Cappello (2013)Crude Oil Biodegradation in the Marine Environments Biodegradation - Engineering and Technology.

Nilanjana Das and Preethy Chandran (2011)Microbial Degradation of Petroleum Hydrocarbon Contaminants: An Overview Biotechnology Research International.

Olajire and Essien J Pet (2014) Aerobic Degradation of Petroleum Components by Microbial Consortia Environ Biotechnol, 5:5.

Shigeaki Harayama, Yuki Kasai and Akihiro HaraMicrobial (2004) communities in oil-contaminated seawater Current Opinion in Biotechnology, 15:205–214.

THANK YOU…