Enzymatic Bioremediation of Petroleum

Petroleum Bioremediation – Employing microorganisms in bioremediation has been a common practice for the past few years. However, relying solely on microorganisms for the degradation procePetroleum bioremediation is an environmentally friendly process that involves the use of microorganisms and enzymes to degrade and remove hydrocarbons from contaminated sites.ss may not be feasible since it is a slow process. Enzymes help to catalyze the conversion of substrates into products by providing favorable conditions for lowering the reaction’s activation energy. At least one polypeptide moiety makes up both proteins and glycoproteins. They function as catalysts for many biochemical processes found in microbial degradation. 

Oxygenases, Laccases and Hydrolases

Enzymatic bioremediation depends on the enzymes’ efficiency. This process is safe as it does not produce toxic byproducts during remediation, and it may also be performed on nutrient-deficient soils. Furthermore, recombinant DNA technology can help to create more stable and active enzymes at lower costs and in larger quantities. This makes using enzymes more appealing and productive. Enzymes may be affected by various external factors, resulting in decreased activity. Immobilization methods are used to overcome this situation. Oxygenases, laccases, and hydrolases can perform bioremediation of petroleum. This article compares the activities of these enzymes.  

Laccases – Petroleum Bioremediation

Laccases refer to polyphenol oxidases containing four ions of copper. This catalyze the cleaving of aromatic compound rings to produce free radicals by reducing one oxygen molecule. Initially studied, laccases are dispersed throughout higher plants and animals and can also be found in bacteria, fungi, and insects.

Laccases are polymeric. They oxidize phenolics and methoxy-phenolic acids and decarboxylate their methoxy groups. Intracellular and extracellular laccases produced by numerous microorganisms catalyze the oxidation of lignins, aryl diamines, aminophenols, para-diphenols, polyamines, polyphenols, and ortho-diphenols. 

Immobilizing laccases onto glass beads can increase their resistance to proteases, enzyme half-life, and stability. Recombinant laccases produced via Trametes Versicolor immobilized on glass beads containing pores have higher bioremediation qualities for petroleum-based materials like amine-containing aromatics, heterocyclic aromatic compounds, and phenolic compounds. 

Hydrolases 

Petroleum bioremediation using hydrolases involves cleaving toxic compounds into less harmful compounds, reducing their toxicity. Petroleum bioremediation involves five types of hydrolases: haloalkane dehalogenases, phosphotriesterases, carboxylesterases, cellulases, and lipases. Lipases can be used to break down triglycerol into glycerol and fatty acids for achieving bioremediation of polyaromatic hydrocarbons (PAHs). Lipases can degrade hydrocarbons in polluted soils. Researchers have reported that a fungal species named P. aeruginosa produces lipase, which can be utilized for petroleum bioremediation.

Biological indicators for studying petroleum hydrocarbon degradation in organisms can be provided by using esterases and lipases. Esterases can degrade alkane and aromatic rings in bacterial and fungal isolates. Haloalkane dehalogenases degrade halogenated aliphatic compounds such as 1,2,3-Trichloropropane. 

Hydrolases are non-selective, well-tolerating, readily available, and lack a cofactor stereo-selectivity. These factors make hydrolases very effective in oil spill biodegradation. Researchers have reported that entrapping organophosphorus hydrolase in the bacterial membrane enhances the catalytic rate of parathion hydrolase.

Enzymes from purified and partially purified bioremediation do not require the growth of a particular microorganism in a polluted environment, but they require catalytic activity. Microbial biotransformation generates toxic side products, as opposed to environmentally friendly enzymatic biotransformation. Although enzymes are more specific to their substrate than bacteria, they are smaller and mobile, making them more efficient at attacking their target.

Oxygenases 

An oxygenase (EC 1.13, 1.14) catalyzes oxygen transfer from molecular oxygen to organic or inorganic substrates using coenzymes line NADPH, NADH, and FAD. Oxygenases can transform and mineralize aromatic compounds such as chlorinated biphenyls and aliphatic olefins. Raising the water solubility or reactivity of aromatic compounds degrades them.

Furthermore, the addition of oxygen atoms to compounds through monooxygenases not only breaks their aromatic rings, but also enables the biotransformation, ammonification, dehalogenation, biodegradation, hydroxylation, denitrification, and desulfurization of aliphatic and aromatic compounds. One of the most distinctive monooxygenase enzymes, methane monooxygenase, is capable of digesting heterocyclic hydrocarbons, aromatics, ethers, cycloalkanes, haloalkanes, methane, alkenes, and alkanes.

The P450 monooxygenase enzyme produced by the Bacillus metaterium bacterium can catalyze the degradation of aromatic substances. Dioxygenases catalyze the transformation of aromatics to aliphatic substances. Pseudomonas putida produces Toluene Dioxygenase to catalyze the toluene (VOC) degradation.

Peroxidases (for example, hydrogen peroxide) produce reactive free radicals after the oxidation of organic compounds. Peroxidases (oxidizing agents) that contain hydrogen peroxide oxidoreductase donors are widespread in the environment. These can be classified as heme peroxidases and non-heme peroxidases. These are found in animals, plants, prokaryotes, and viruses, and are involved in hormone regulation, immune responses, and other biological processes in mammals. Since peroxidases are thermoplastic, they can oxidize a wide range of substrates. 

Future research focus

Rapidly accumulating in the environment, crude oil spillages are a menace to the environment and pose a significant risk to the health of many organisms. Therefore, the degradation of these contaminants can have a significant impact on reducing petroleum toxicity. To improve the bioremediation of petroleum by laccases, several future research directions can be considered.

One example of future research in genetic engineering approaches for petroleum bioremediation would be directed evolution. This in-lab technique utilizes Darwinian selection and mutation techniques to examine, adjust enzyme-substrate specificity, and enhance bio-catalysis. Additionally, future research can be directed towards site-directed mutagenesis, which utilizes homologous genetic sources to identify and mutate key gene regions by rational design. 

Scientists can use genetic engineering to achieve various goals by mutating specific sites of a gene or performing iterative mutations at specific locations. Additionally, researchers can consider metabolic engineering as a focus area for future research to enhance the production of a specific cellular compound and modify an organism’s genetic and regulatory system for petroleum bioremediation.