Use of biotechnology in the removal of Oil and Grease deposits
The oil spills from oil tankers on land surface as well as in seas and oceans are a major environmental hazard. This not only kills the aquatic flora and fauna by destroying the habitat but also creates health problems for the local inhabitants. Traditionally chemical dispersants are being used as remediation efforts. However these chemical dispersants are also toxic in nature and they persist in the environment for a long time. The present techniques of washing the oil off the gravel and cleaning the area of oil spills, is very expensive and time consuming. In order to overcome some of these problems, the oleophilic fertilizers are being developed which allow rapid growth and multiplication of microbes which further leads to the increase in the biodegradation process for removal of oil. In recent years, using genetic engineering, oil utilizing microorganisms have been produced which can grow rapidly on oil. The genetically engineered microbes for cleaning oil spills are mixed with straw. At the site of oil spill, the straw mixed with microbes are scattered over the oil spilled area. The straw soaks the oily water and the microbes break the oil into non-toxic and non polluting materials thereby cleaning up the site.
Some of the oil utilizing microbes can also produce surface active compounds that can emulsify oil in water and thereby removing the oil. A strain of Pseudomonas aeruginosa produces a glycolipid emulsifier that reduces the surface tension of oil-water interface which helps in the removal of oil from water. This microbial emulsifier is nontoxic and biodegradable and has shown promising results in the laboratory experiments.
Some of the microorganisms which are capable of degrading petroleum include pesudomonads, various corynebacteria, mycobacteria and some yeasts. The two methods for bioremediation of oil spills are: a) using a consortium of bacteria, and b) using genetically engineered bacteria/microbial strains. (discussed under the topic of bioremediation) Both bacterial and fungal cultures from the petroleum sludge have been isolated. The fungal culture could degrade 0.4% sludge in 3 weeks. Degradation of petroleum sludge occurred within two weeks when the bacterial culture (Bacillus circulans CI) was used. A significant degradation of petroleum sludge was observed in 10 days when the fungus + B. Circulans and a prepared surfactant were exogenuously added to petroleum sludge.