Petroleum Hydrocarbon Degradation

STIMULATION OF PETROLEUM HYDROCARBON DEGRADATION IN SOIL

GAYATHRI.M

DATE OF SUBMISSION:19-12-2017.

ABSTRACT:

Hydrocarbon are mainly the pollutants from oil refineries and oil spills. These pollutants can be degraded by a consortium or cocktail of microorganisms e.g. pseudomonas, Corynebacterium, Arthobacter, Mycobacterium and nocardia. Biodegradation has at least three outcomes (1) a minor change in an organic molecule, leaving the main structure still intact;(2) Fragmentation of a complex organic molecule in such a way that the fragments could be reassembled to yield the original structure; and (3) complete mineralisation, which is transformation of organic molecules to inorganic forms. In the laboratory experiments,

There are several 100 individual components in every crude oil and the composition of each varies with its origin. Most xenobiotic pollutants can be regarded as substituted (or) modified hydrocarbons. Susceptibility to biodegradation varies with type and size of the hydrocarbon molecule. Fuel and lubricating oil spills have become a major environmental hazard to-date. The extent of hydrocarbon biodegradation in contaminated soils is critically dependent upon three factors: a) the creation of optimal environmental conditions to stimulate biodegradative activity, b) the predominant Petroleum hydrocarbon types in the contaminated matrix and c) the bioavailability of the contaminants to microorganisms. The Petroleum hydrocarbon degradation is also affected by the molecular composition of the hydro carbons. Microorganisms with the ability to degrade crude oil are ubiquitously distributed in soil and mine environments. Dehydrogenase enzyme involves in this to remove the oxidative substrate, and has been found in correlation with the oxygen uptake and organic substrate removal rates in aerobic

Samples were transported in coolers to the laboratory, and stored at −20°C until they were analysed. Soil samples were sieved moist using a 2-mm mesh screen and thoroughly mixed. 10 g of soil was added to 95 ml deionized water containing 2 drops of Tween 80 and then was incubated and shaked for 30 min at room temperature. The mixture prepared is called soil solution. A 100 ml Erlenmeyer (flask 1) was prepared containing 2.5 ml soil solution and 95 ml of mineral salt medium (MSM) (KH2PO4, 1.52 g; Na2HPO4, 2.44 g; CaCl2.2H2O, 0.50 g; MgSO4.7H2O, 0.20 g; (NH4)2SO4, 0.50 g; trace element, 10ml) and 2.5ml of synthetic mixture of petroleum hydrocarbons (gas oil, kerosene, furnace oil; 1:1:0.1) as sole source of carbon. The flask was incubated at 22 ± 2 o C. After 15 days, 2.5 ml of flask1 was transferred to a second flask (flask 2) with the same condition as flask 1. These incubating -transferring were repeated for 4 times. The experiments were carried out with soil from an uncontaminated area around were the sample is collected. The soil samples were sieved by a 2-mm screen and were sterilized three times by autoclaving at 200 o C for 30 min followed by incubation for 24 h at 37 o C. Six 250 ml Erlenmeyer flasks were prepared for each of the soils