20-03-2014, 11:12 AM
BIODEGRADATION OF DIESEL BY AEROMONASHYDROPHILA
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Abstract
Hydrocarbon degrading microorganisms play a major role in the environment.. The purpose of the present study was to enumerate of Aeromanas sp from oil contaminated soil and to study degrading capacity, emulcification activity and production of biosurfactant. The hydrocarbon substrate specificity test shown that diesel is also one of the best substrate for growth and emulsification of biosurfactant by Aeromonas. Among 6 strains of Aeromonas, frist strain(A1) shows maximum degradation rate at end of 168 hrs upto19.37% followed by other strains, about 75% of diesel was degraded by Aromonas over a period of 7days. Emulsification upto 75% by A1 followed by A2(63.75%) ,A3(57.5%), Biosurfactant production by A1 strain 0.064g/1 followed by other strains it represents a new type of biosurfactant with strong emulsifying ability.
INTRODUCTION
Biodegradation is the partial or complete conversion of the compound of interest to its elements. The role of organisms, both micro-and macro-organisms, in biodegradation is complex. It is a function of the organism’s presence in an environment, their ecology, their metabolism (enzyme complement and efficiencies), growth rate and kinetics (of both growth and metabolism). It has been known for several decades that microorganisms possess both aerobic and anaerobic degradation. Microorganisms are actively involved in the degradation of several naturally occuring and toxic substances such as petroleum hydrocarbons, pesticides etc., Aerobic biodegradation is the breakdown of organic contaminants by microorganisms when oxygen is present. Aerobic bacteria use oxygen as an electron acceptor, and break down organic chemicals into smaller or organic compounds, often producing carbon dioxide and water as the final product. Aerobic biodegradation is also known as aerobic respiration. Aerobic biodegradation is an important component of the natural attenuation of contaminants at many hazardous waste sites. Anaerobic biodegradation is the breakdown of organic contaminants by microorganisms when oxygen is not present. Some anaerobic bacteria use nitrate, sulfate, iron, manganese, and carbon dioxide as their electron acceptors. And break down organic chemicals into smaller compounds, often producing carbon dioxide and methane as the final products. Anaerobic biodegradation is an important components of the natural attenuation of contaminants at many hazardous waste sites.
Distribution of hydrocarbon degrading microorganisms
It has been known for several years that certain microorganisms are able to degrade petroleum hydrocarbons and use them as sole source of carbon and energy for growth. The ability to degrade and/or utilize hydrocarbons substrates is exhibited by wide variety of bacterial genera, 25 genera of hydrocarbon degrading bacteria (Floodgate, 1984) have been isolated from the marine environment. Similarly 22 genera of hydrocarbon degrading bacteria have been reported (Bossert and Bartha, 1984) based on the number of published.
Microbial remediation of toxic hydrocarbon contaminated sites is carried out by a diverse group of microorganisms. Study of this diversity at the genetic level is necessary to understand the phylogenetic perspective, the mechanism of degradation, and develop novel strategies of treatment. Analysis of microorganisms having high specificity for recalcitrant compound. Documentation of this microbial diversity from oily sludge/crude oil contaminated sites is essential because they create a major environmental concern and these microbes can be used for cleaning up the same ().
Characteristics of diesel
One can obtain diesel from petroleum, which is sometimes called petrodiesel when there is a need to distinguish it from diesel obtained from other sources. As a hydrocarbon mixture, it is obtained in the fractional distillation of crude oil between 2500C and 3500C at atmospheric pressure. Diesel is generally simpler to refine than gasoline and often costs less (through price fluctuations often mean that the inverse is true).
Reducing the level of sulfur in diesel is better for the environment. It allows the use of catalytic diesel particulate filters to control diesel particulate emissions, as well as more advanced technologies, such as Nox absorbers (still under development), to reduce emissions of nitrogen oxides (Nox). However, lowering sulfur also reduces the lubricity of the fuel, meaning that additives must be put into the fuel to help lubricate engines. Diesel contains approximately 18% more energy per unit of volume than gasoline, which along with the greater efficiency of diesel engines contributes of fuel economy (distance traveled per volume of fuel consumed). In the maritime field various grades of diesel fuel are used.
IMPORTANCE OF THE PRESENT INVESTIGATION
Petroleum hydrocarbon continues to be used as the principle source of energy. Wide scale production, transport use and disposal and petroleum globally have made it a major containment in both prevalence and quantity in the environment. Biosurfactant are a group of surface-active molecules produced mainly by hydrocarbon degrading microorganism it can degrade or transform the components of petroleum products. They are non-toxic, non–hazardous, Biodegradable and environmentally friendly components. Hence, reclamation of petroleum hydrocarbon polluted sites can be carried out by bioremediation, which is can enhance natural process of biodegradation using biosurfactant producing and oil degrading bacterial cultures. Bioremediation technologies generally aim at providing favourable conditions of certain, temperature and nutrients to enhance biological hydrocarbon break down.