Biodegradation and Bioconversion of Hydrocarbons

This chapter outlines an established approach for hydrocarbon analysis in sediments, the sources of hydrocarbons in the marine environment, and the importance of understanding the sedimentary environment of deposition and the reservoir of contaminants it can represent. To supplement national monitoring programmes, government and industry have commissioned work on polycyclic aromatic hydrocarbons in several United Kingdom estuaries, including Milford Haven Waterway, Southampton Water and Sullom Voe. These areas have some of the longest-established and largest oil industry sites in the UK, and they have been monitored intensively and successfully through most of their histories as oil, gas and petrochemicals ports. However, few economically and ecologically important UK estuaries and coastal zones have a particularly long history of advanced chemical “fingerprinting” to assist monitoring the specific sources, fates and effects of sediment hydrocarbons. As such, the UK approach has not compared well with the efforts of the United States of America in terms of apportionment of contaminant sources, albeit driven in part by the latter’s focus on litigation. As well as distinguishing natural and anthropogenic inputs from background conditions, hydrocarbon fingerprinting methods can directly improve the ability to discriminate between individual hydrocarbon sources using knowledge of their composition, age and relative weathering. An understanding of the manufacturing processes and their chronology can help discriminate among multiple sources of pollutant hydrocarbons and also contribute to life cycle analysis and studies of product footprints. There is a need to track the ubiquity, fate, persistence and effects of hydrocarbons and petrochemicals in the environment. However, the use of fingerprinting faces challenges that include high cost, potentially unwelcome discovery of liability, sediment movements and patchiness, biodegradation effects on clarity of the fingerprint, and over-printing by chronic inputs from non-point sources such as air pollution and river runoff.

Polycyclic aromatic hydrocarbons (PAHs) comprise a class of organic compounds of petrogenic origins or generated from the incomplete combustion of organic matter. Their presence in the environment can be a source of food contamination, which implies a potential risk to human health according to the International Agency for Research on Cancer. Additionally, the Food and Agriculture Organization of the United Nations (FAO/WHO) and the Scientific Committee on Food consider PAHs to be genotoxic and carcinogenic. The greatest concern has been raised regarding the possibility of cancer induction in humans exposed to PAHs from contaminated food. Therefore, many regulations and reports regarding strategies for and results of food monitoring have been published, including performance criteria for the sampling, chemical analysis and maximum permitted levels of these contaminants in food. A variety of techniques have been reported for the extraction, clean-up and determination steps of the analytical process. The details and advantages of each technique are discussed in this chapter. Additionally, because method validation is one measure that laboratories must implement to guarantee the reliability, traceability and comparability of their results, a review and critical analysis of the current practices in this area are also presented.

Hydrocarbons and associated derivatives are unavoidably common in the environment. The use of crude oils, petrol, diesel, heavy oils, lubricants etc. has continued to cause widespread aquatic, terrestrial and even atmospheric pollution. Considering the importance of hydrocarbons in various industries, its occurrence in natural and blended forms is inevitable. However, possible recovery of systems contaminated with hydrocarbons has given rise to the interest on the degradation of hydrocarbons, especially in a biologically-driven process known as biodegradation. Therefore, the Chapter will provide an overview of the basic behaviour of hydrocarbons in the environment, chances of biological degradation and factors pivotal for biodegradability. Similarly, among other issues related to biodegradation of hydrocarbons, the core remediation techniques (bio-, chemico-, and physico-treatments) adopted in most hydrocarbon biodegradability ventures are evaluated alongside the evaluation of the mechanisms of degradation. The use of plant technology in the remediation of polluted sites often referred to as phytoremediation is one of the options employed for the bio-recovery of hydrocarbon-impacted systems due to the various mechanisms involved. Therefore, regardless of the fact that some phyisco-chemically driven processes of hydrocarbon removal are abundantly used at some contaminated sites, none has been as green, cost effective and sustainable like the adoption of a biodegradation process.

Polycyclic aromatic hydrocarbons (PAHs) present in the petroleum wastewater are ubiquitous environmental pollutants. They are generated from both natural and anthropogenic processes, and pose a serious concern on the health of aquatic life and human beings through bioaccumulation. PAHs are known to be cytotoxic, mutagenic and carcinogenic. They persist in the environment due to their hydrophobic nature and are difficult to treat using chemical methods. This chapter details the biodegradation of PAHs under extremophilic condition. Bacteria, fungi and algae are reported to be used in the treatment of PAHs. Extremophilic conditions such as acidophilic (pH 1–5), alkaliphilic (pH > 9) halophilic (>3 % salt), thermophilic (temperature > 50 °C), psycrophilic (temperature < 10 °C), piezophilic or barophilic (pressure > 38 MPa) and xerophilic (a_w 0.60–a_w 0.90) conditions. Collection of samples, isolation of extremophilic micro-organism, mineralization of hydrocarbons and identification of microbes using molecular techniques are detailed. Despite the microbial ability to degrade petroleum hydrocarbons, there are factors such as temperature, pH and nutrients that influence the degradation of hydrocarbons. Information on mechanisms and pathways for petroleum hydrocarbon degradation under extreme conditions is scarcely known and recently few studies reported on enzymes, genes and metabolism of hydrocarbons. Microbial cell interaction with petroleum hydrocarbons are also detailed in this chapter. Extremophiles play a vital role in the degradation of petroleum hydrocarbons and in the treatment of refinery wastewater.

Global industrialization has largely expanded the edges of petroleum hydrocarbon (PHC) exploration. A large amount of various hydrocarbons are introduced into the environment during the stages of oil extraction, refinement, storage, transportation and disposal. Benzene is the parent hydrocarbon among the aromatic organic compounds which naturally occurs in petroleum products. It is a well-known carcinogenic organic compound. Its contamination is a widespread problem in soil as well as groundwater due to lack of oxygen in subsurface soils. Various physical and chemical methods are known to clean up aromatic hydrocarbons but they are too expensive and lead to adverse effects. Bioremediation technology has gained a great attention for the cleanup of hazardous aromatic compounds. There are advantages to rely on indigenous microorganisms rather than adding microbes to degrade waste. Emerging technologies have been developed in the field of environmental biotechnology for enhance degradation and complete removal of organic contaminant. This chapter reviews on recent progress in anaerobic degradation of benzene along with its sources, environmental fate and anaerobic mineralization pathways in the presence of different electron acceptors and also focuses on enhanced benzene degradation by enrichment and immobilization-based culture technique, factors affecting the rate of anaerobic degradation, role of enzymes and molecular tools to assess bioremediation.

Over the last hundred years, fossil fuels consumption has increased dramatically leading to a significant increase in greenhouse gas emissions, the depletion of natural reserves of fossil fuels and increase fuel production costs. Consequently, renewable and sustainable fuel sources such as bio-oil are receiving increased attention. In bio-oils, such as microalgae oil, triglycerides and fatty acids are sustainable resources with high energy densities that can be converted into liquid hydrocarbon fuels, efficiently. One of the efficient ways for bio-oil conversion to applicable fuels is catalytic hydro-cracking. This chapter presents research on the catalytic conversion of oleic acid (main component in all types of bio-oil) in bio-oil to liquid hydrocarbon fuels employing two catalysts. These catalysts include Ni-ZSM-5 and Ni-Zeolite β, which were prepared by impregnating cheap catalyst supports (ZSM-5 and Zeolite β) with Ni(NO₃)₂·6H₂O calcined at a temperature of 500 °C. The catalysts were characterized using the Brunauer–Emmet–Teller Nitrogen Adsorption technique, scanning electron microscopy (SEM) and SEM–EDX (energy-dispersive X-ray spectroscopy) to analyse nickel impregnation and measure surface areas and pore size distribution. Conversion rates of oleic acid and product yields of liquid hydrocarbon fuels using each catalyst sample were determined via hydro-cracking reactions run at a temperature range of 300–450 °C and under a 30 bar pressure.

Nowadays air pollutants are becoming more widespread as the pace of industrial activity accelerates. Emission inventories reveal that atmospheric pollutant emissions have continuously increased since the beginning of the twentieth century, with volatile organic compounds (VOCs) representing about 7 % of these emissions. Despite this relatively low emission share, VOC emissions represent a major environmental and human health problem since most VOCs can be toxic depending on the concentration and exposure time and they also contribute to substantial damage to natural ecosystems. The negative effects of VOCs on human health and natural ecosystems have therefore led to stricter environmental regulations worldwide. VOCs emitted from industrial facilities are usually volatile hydrocarbons (VHs), which are extensively used in manufacturing processes. Among the available technologies for VHs treatment, biological processes in many cases constitute the most cost-effective technology for treating low pollutant concentrations and their implementation at industrial scale is growing exponentially. Unfortunately, several VHs can produce toxic effects to the microbial communities, leading to inhibition issues as in the case of aromatic compounds. Furthermore, some VHs used as monomers in the plastics industry or as industrial solvents exhibit a very low aqueous solubility, leading to mass transfer issues and poor removal performance. Two-phase partitioning bioreactors (TPPBs) emerged as innovative multiphase systems capable of overcoming the key limitations of traditional biological technologies such as the low mass transfer rates of hydrophobic VOCs and microbial inhibition at high pollutant loading rates. This work presents an updated state-of-the-art on the advances of TPPB technology for the treatment of VHs. The fundamentals of TPPB design, operation, microbiology and mass transfer are reviewed. Niches for future research, opportunities for TPPB optimization and challenges towards full-scale applications are identified and discussed.

As a result of global industrialization and increasing population there has been an alarming increase in the global demands for energy which is being fulfilled by exploiting various natural resources significantly hydrocarbons. As a result enormous amounts of hydrocarbons and hydrocarbon-based products have been released into the environment, threatening health and sustainability of the ecosystem. These different types of hydrocarbon-contaminated environments vary in their microbial composition and serve as an excellent reservoir of microbial flora, with a potential to degrade hydrocarbons and produce biosurfactants. In this chapter, an overview of biosurfactant-producing microorganisms from hydrocarbon-contaminated environments and their role in utilisation and degradation of hydrocarbon compounds is presented. Micro-organisms growing in hydrocarbon-rich environments undergo many adaptations, such as production of biosurfactants, which increases access to these hydrophobic substrates. Industrially, biosurfactants, which constitute as a group of surface-active amphiphilic compounds, are of great significance as they are biodegradable and nontoxic compared to synthetic chemical surfactants. Thus, biosurfactants have found wide applications and are used in bioremediation, oil exploration and enhanced recovery, health care, oil and food processing industries.

Crude oils vary in their physical properties, chemical composition and between fields of origin; of special importance are the relative amounts of high and low molecular weight compounds present in crude oils. Heavy oils contain a greater percentage of high molecular weight components. The low biodegradation rates of heavy oils probably reflect the resistance of the complex high molecular weight components to microbial degradation. Hydrocarbons are water insoluble substrates that often need to be emulsified prior to their degradation by microbes. Emulsification is an important phenomenon among those parameters which influence the fate of crude oil. It has been accepted that the microorganisms developing on hydrocarbons produce surface-active agents, or biosurfactants, which emulsify the substrate, enabling its transfer into cells. Biodegraded hydrocarbons can provide bio-corrosive microbial communities with an important source of nutrients. Hence, occurrence of some hydrocarbon-degrading bacteria in oil reservoir/petroleum transporting pipelines influence electrochemical corrosion reactions. These isolates able to cause corrosion of carbon steel. Microbiologically influenced corrosion is a problem commonly encountered in facilities of the oil and gas industries. New insights into microbial corrosion processes may be achieved through understanding of the interaction between biodegradation and corrosion of carbon steel in crude oil reservoir/transporting pipelines. In this chapter, the interaction between hydrocarbon-degrading bacteria on corrosion of carbon steel are elucidated. The role of biodegradation on corrosion was confirmed by gas chromatography–mass spectrometry, X-ray diffraction, electrochemical impedance spectroscopy and weight loss analyses. The potential of this consortium was evaluated for the bioremediation of oil-contaminated environments.

Petroleum or crude oil is a crucial source of energy and one of the main factors driving the World’s economy. The progressive depletion of high-quality crudes in the last decades will make necessary the exploitation of unconventional low-quality heavy and extra-heavy crudes to meet future energy demands. However, their exploitation requires the application of special techniques in order to facilitate their recovery, transportation and refining. Chemical and thermal methods commonly employed (e.g. use of gases, polymers or solvents; hydraulic fracturing; in situ combustion) are expensive and environmentally hazardous. The application of biological treatments to reduce the viscosity and density of unconventional oils can be a cheaper and environmentally friendly alternative or a complementary technology. The bioconversion of crude oil is a process where heavy oil fractions are converted into lighter ones due to the action of microorganisms or enzymes, resulting in an enrichment in lighter hydrocarbons. However, it is necessary to select microorganisms and enzymes with the ability of degrading preferentially the heavy oil fractions (long chain alkanes, aromatics, resins and asphaltenes). As a result, the oil viscosity is reduced (usually from 10³–10² cP up to 10 cP) and its mobility is improved, which contributes to increase oil recovery efficiency and, at the same time, increases the quality of the oil. This chapter will review the latest advances in the use of biological treatments to reduce the viscosity and improve the quality of heavy crude oils.

Bacteria with the abilities to degrade crude oil were isolated from soil, activated sludge and biological treatment lagoon of the local petrochemical industries. For the biodegradation process, n-alkanes, of varying carbon chain length, C₁₆–C_38, were used. Out of the 12 cultures of bacteria isolated, 3 of the best oil degraders were partially identified via biochemical tests; 2 of which were Acinetobactor spp while another one belonged to Proteus sp. Degradation of the n-alkanes in crude oil was monitored under agitated and non-agitated condition using gas chromatography technique. Generally, non-agitated cultures showed higher degradation rates. One of the Acinetobacter sp. showed the highest degradation rate, in which 80–100 % of the alkanes (C₁₆–C₃₈) in crude oil was degraded without any addition of organic nitrogen and phosphorus. It is of interest to highlight another of the Acinetobacter sp. which showed the ability to degrade longer chain alkanes more rapidly than shorter ones; C₃₆ and C₃₈ were fully degraded in 2 days. Only one bacterium, Proteus sp showed increased rates of degradation under agitated condition.