Study Notes on Biodegradation of Hydrocarbons

The below mentioned article provides study notes on Biodegradation of Hydrocarbons.

Hydrocarbons can generate significant pollu­tion because they are among the most com­mon contaminants of groundwater, soil and sea when oil is spilled (Mohn 1997). The damage caused by oil spills in marine or freshwater systems is usually caused by the water-in-oil emulsion.

Various types of microorganisms can degrade hydrocarbons: bacteria, yeasts, filamentous fungi, but none of them degrade all of the possible hydrocarbon molecules at the same rate.

Each organism may have a differ­ent spectrum of activity and a definite prefer­ential use of certain chain lengths hydrocar­bon structures. Almost all petroleum hydro­carbons can be oxidized to mainly water and carbon dioxide, but the rate at which the pro­cess takes place is dependent on their nature, amount and the physical and chemical prop­erties that influence their persistence and bio- degradability.

Hydrocarbons are subject to both aerobic and anaerobic oxidation. Usually, the first stage of biodegradation of insoluble hydrocarbons is predominantly aerobic, while the organic carbon content is reduced by the action of anaerobic organisms. The prevailing environmental factors and the types, numbers and capabilities of the mi­croorganisms present affect the biodegradation occurrence and rate.

Factors affecting hydro­carbon biodegradation in contaminated soils can be:

a. The occurrence of optimal environmental conditions to stimulate bio-degradative ac­tivity

b. The predominant hydrocarbon types in the contaminated matrix; the bioavailability of the contaminants to microorganisms

c. Dispersion and emulsification enhancing rates in aquatic systems and absorption by soil particulates.

Hydrocarbons have different solubility in water where they are only degraded. Due to different hydrophobicity and low solubility in water of the hydrocarbons, the process should be intensified by enhancing physical contact between microorganisms and oil by adding adjuvants to improve the contact areas or by injecting of mixtures of microorganisms, dur­ing the so-called bio-augmentation.

It is also known that the activity of bacte­ria and fungi able to oxidize hydrocarbons could be improved by supplementation with various nutrients (sources of nitrogen and phosphorous). Different organisms need dif­ferent types of nutrients. Bio-enhancement is applied to stimulate the activity of bacteria already present in the soil at a waste site by adding different nutrients).

Bio-sorption:

Bio-sorption is a fast and reversible process for the removal of toxic metal ions from waste water by live or dried biomass, which re­sembles adsorption and in some cases ion ex­change. The bio-sorption offers an alternative to the remediation of industrial effluents as well as the recovery of metals contained in other media.

Bio-sorbents are prepared from naturally abundant and waste biomass. Due to the high uptake capacity and very cost-ef­fective source of the raw material, bio-sorption is a progression towards a perspective method.

It has been demonstrated that both living and non-living biomass may be utilized in biosorptive processes, as they often exhibit a marked tolerance towards metals and other adverse conditions. Metal ions can bind to cells by different physiochemical mechanisms, de­pending on the bacterial strain and environ­mental conditions. Because of this variability, current knowledge of these processes is incom­plete.

In general, bacterial cell walls are poly- electrolytes and interact with ions in solution so as to maintain electro neutrality.

The mecha­nisms by which metal ions bind onto the cell surface most likely include electrostatic inter­actions, van der Waals forces, covalent bond­ing, redox interactions, and extracellular pre­cipitation, or some combination of these pro­cesses.

Bio-sorption of heavy metals by algal biomass is an advantageous alternative, an ap­propriate and economically feasible method used for wastewater and waste clean-up, be­cause it uses algal biomass sometimes consid­ered waste from some biotechnological pro­cesses or simply its high availability in coastal areas makes it suitable for developing new by-­products for waste water treatment plants.