BIODEGRADATION OF CRUDE OIL

Abstract

The pollution of marine environment bycrude oil has beenfocussedbyanumber of events in recent years. The oil spills of American tanker in Alaska, Iranian oil tanker in Moracco, and the recent Persian Gulf war have more than brought out the importance of such ecological disasters. Numerous technological advancements have been recom mended to contain this menace. One of important processes of removingoil from the spills is by utilizing natural biodegradation through microorganisms such as bacteria, fungi and yeast. Many environmental factors influence the oxidation of hydrocarbons even when the microorganisms of proper specificity are available. In the investigations presented in this dissertation a number of oil degrading microorganisms were isolated and identified from effluents and contaminated soil. They have been experimented upon in the laboratory mock up for exploring their potential. About 22 bacteria and 11 fungi were obtained from soil and 17bacteria and 7 fungi from petrochemical effluents. Bacteria were identified to the generic level by morphological and biochemical tests whereas for fungi identification was done bymicroscopic examination and staining. Among the isolates, six bacteria and four fungi were selected on the basis of pronounced growth viz. Bacillus megaterium. Bacillus pumilus, Curtobacterium spp., Enterobacter sakazakii. Micrococuss roseus, Pseudomonas spp., Aspergillus niger, Cladosporium sphaerospermum. Fusarium lateritium. and Penicillium purpurogenome. Effect of physico-chemical parameters such as substrate concentrations, aeration, pH, Nitrogen sources in various forms, phosphate concentration on the growth of selected bacteria and fungi was investigated. Growth was measured by bacterial enumeration (7 days growth) and drymass (15 days growth) for fungi. The growth pattern of bacteria indicate that the log period was well defined and that it extends upto the 10th day. The fungi on the other hand, show log periods between 10th-25 th day with reducing slopes. It was interesting to note that in certain cases growth accompanied by emulsificationwas evident in the form of colloidal suspension of droplets. Assimilation of crude oil in selected species of bacteria and fungi monitored by transmission electron microscopy, of protein estimation and oxygen uptake apart from determining numbers and dry mass was restored to demonstrate their capacities in hydrocarbon degradation. Transmission electron microscopy revealed: - disappearance of envelope in Gram's negative bacteria, - increase in thickness of cell wall in both bacteria and fungi - oil inclusions in the cells, - presence of peroxisomes in fungal strains. Protein analysis demonstrated that the amount is not as much as in cells grown on other media. Furthermore the amount of protein in Gram's - ve bacteria was less as compared to Gram's+ve bacteria. Respiratory activity (Q02) monitored employing the manometric technique showed oxygen consumption with some n-alkanes and aromatic hydrocarbons, glucose and crude oil. Significant differences were observed in the rate of oxygen uptake with various substrates. The ability of microbes to degrade a heavy crude oil, .which contained about 50% NSO, and asphaltene has been demonstrated. The potential of these microorganisms and concomitant decrease inpH and reduction in oil fractions was observed. The residual oil was separated into class fractions through solvent elution bysilica alumina chromatography and high performance liquid chromatography, (HPLC). The results show that the tested microbes were able to grow utilizing fractions of crude. An overall utilization of 47-58% crude with 78-90% alkanes and 77-90% aromatic was established. All the tested microbes used in this study showed continued activity until about the end of 30 days. The result however, showed that the most outstanding changes were noticed during the first 10 days in bacteria and 10 - 15 days in fungi. Though every care has been taken in the isolation , identification of microbes and measurement of their degradingcapabilities the author may have missed some salient details which may only be taken as a shortcoming of work .