Degradation Of Long-chain Alkanes Research Articles

Mechanism and kinetic study of n-undecane degradation on Co-CeO2: A dual approach combining thermal and plasma catalysis

The catalytic degradation of long-chain alkanes presents a formidable challenge in environmental chemistry. n-Undecane (C11), a quintessential long-chain alkane, predominates as a component of volatile organic compounds (VOCs) emitted from the printing industry and diesel-powered vehicles. The uncontrolled release of these compounds into the atmosphere necessitates stringent measures. This study reports on the plasma-catalytic degradation of n-undecane over the CeO2 based catalysts cooperated with cobalt (Co), manganese (Mn), aluminum (Al), nickel (Ni), iron (Fe), or magnesium (Mg) via aerosol pyrolysis method. Notably, the Co-doped CeO2 catalyst with a Co:Ce atom ratio of 4:1, in conjunction with plasma, achieves an optimal degradation performance. Under the reaction conditions of 90 °C and an energy density of 40 J/L, C11 conversion and COx selectivity reached impressive levels of 100 % and 97 %, respectively. Characterization findings indicate that elevated ratios of Ce3+/(Ce3++Ce4+) and Co3+/(Co2++Co3+) are conducive to the catalytic degradation of C11. Kinetic models have been developed to elucidate the thermal and plasma catalytic degradation mechanisms

Long-lasting degradation of long-chain alkanes through activating Bacillus-like microbes after Fenton pre-oxidation in soil

To explore the effects and mechanisms of long-lasting degradation of long-chain alkanes (C25-C30) in petroleum-contaminated soil, a solid iron catalyst prepared by adding different proportions of (5 % and 15 % (w/w)) chitosan (CS) was used for Fenton pre-oxidation experiment. Bioremediation experiments were performed for 100 days after pre-oxidation. The results indicated that the degradation for long-chain alkanes and Total Petroleum Hydrocarbons (TPH) were 76.95 % and 76.89 %, respectively. Furthermore, long-lasting degradation of long-chain alkanes was achieved by activating Bacillus-like microbes. In each biodegradation cycle, the long-chain alkanes degradation in the active control group increased by 77.39 mg/kg, 76.74 mg/kg, 36.88 mg/kg, and 76.51 mg/kg compared to the previous cycle. Besides, the half-life of long-chain alkanes was 131 days shorter in the active control group than in the inactive control group. Higher microbial enzyme activity for degrading long-chain alkanes was observed after Fenton pre-oxidation because the expression of alkane metabolism genes was activated by the high consumption of dissolved organic carbon. Finally, the dominant bacterial genera in the active control group shifted predominantly to Paenibacillus (13.26 %), Acinetobacter (8.02 %), and Microbacterium (17.64 %). Therefore, this study possesses significant engineering application value.

Genome and metabolome analysis of Bacillus sp. Hex-HIT36: A newly screened functional microorganism for the degradation of 1-hexadecene in industrial wastewater

1-Hexadecene has been detected at a level of mg/L in both influent and effluent of wastewater treatment plants situated in chemical/pharmaceutical industrial parks, which poses a potential threat to the environment. However, few reports are available on aerobic metabolic pathways and microorganisms involved in 1-Hexadecene degradation. In this study, a new strain of 1-Hexadecene-degrading bacteria, Bacillus sp. Hex-HIT36 (HIT36), was isolated from the activated sludge of a wastewater treatment plants located in an industrial park. The physicochemical properties and degradation efficacy of HIT36 were investigated. HIT36 was cultured on a medium containing 1-Hexadecene as a sole carbon source; it was found to remove ∼67% of total organic carbon as confirmed by mass spectrometric analysis of intermediate metabolites. Metabolomic and genomic analysis showed that HIT36 possesses various enzymes, namely, pyruvate dehydrogenase, dihydropolyhydroxyl dehydrogenase, and 2-oxoglutarate-2-oxoiron oxidoreductase (subunit alpha), which assist in the metabolization of readily available carbon source or long chain hydrocarbons present in the growth medium/vicinity. This suggests that HIT36 has efficient long-chain alkane degradation efficacy, and understanding the alkane degradation mechanism of this strain can help in developing technologies for the degradation of long-chain alkanes present in wastewater, thereby assisting in the bioremediation of environment.

Characterization and identification of long-chain hydrocarbon-degrading bacterial communities in long-term chronically polluted soil in Ogoniland: an integrated approach using culture-dependent and independent methods

Escalating oil consumption has resulted in an increase in accidental spills of petroleum hydrocarbons, causing severe environmental degradation, notably in vulnerable regions like the Niger Delta. Complex mixture of these hydrocarbons particularly long-chain alkanes presents unique challenges in restoration of polluted environment due to their chemical properties. This study aimed to investigate the long-chain hydrocarbon-degrading bacterial communities within long-term chronically polluted soil in Ogoniland, by utilizing both traditional cultivation methods and modern culture-independent techniques. Results revealed that surface-polluted soil (SPS) and subsurface soil (SPSS) exhibit significantly higher total organic carbon (TOC) ranging from 5.64 to 5.06% and total petroleum hydrocarbons (TPH) levels ranging from 36,775 ppm to 14,087 ppm, compared to unpolluted soil (UPS) with 1.97% TOC and 479 ppm TPH, respectively. Analysis of carbon chain lengths reveals the prevalence of longer-chain alkanes (C20-28) in the surface soil. Culture-dependent methods, utilizing crude oil enrichment (COE) and paraffin wax enrichment (PWE), yield 47 bacterial isolates subjected to a long-chain alkane degradation assay. Twelve bacterial strains demonstrate significant degradation abilities across all enriched media. Three bacterial members, namely Pseudomonas sp. (almA), Marinomonas sp. (almA), and Alteromonas (ladA), exhibit genes responsible for long-chain alkane degradation, demonstrating efficiency between 50 and 80%. Culture-independent analysis reveals that surface SPS samples exhibit greater species richness and diversity compared to subsurface SPSS samples. Proteobacteria dominates as the phylum in both soil sample types, ranging from 22.23 to 82.61%, with Firmicutes (0.2–2.22%), Actinobacteria (0.4–3.02%), and Acidobacteria (0.1–3.53%) also prevalent. Bacterial profiles at genus level revealed that distinct variations among bacterial populations between SPS and SPSS samples comprising number of hydrocarbon degraders and the functional predictions also highlight the presence of potential catabolic genes (nahAa, adh2, and cpnA) in the polluted soil. However, culture-dependent analysis only captured a few of the dominant members found in culture-independent analysis, implying that more specialized media or environments are needed to isolate more bacterial members. The findings from this study contribute valuable information to ecological and biotechnological aspects, aiding in the development of more effective bioremediation applications for restoring oil-contaminated environments.

An NAD+-dependent group Ⅲ alcohol dehydrogenase involved in long-chain alkane degradation in Acinetobacter venetianus RAG-1

Alcohol dehydrogenases (ADHs) are a class of key enzymes responsible for the oxidation of alkyl alcohols in the aerobic alkane metabolic pathway. Currently, the degradation mechanisms of short- and medium-chain alkanes are commonly reported, while those of long-chain alkanes have received less attention. In this work, a putative long-chain ADH was screened from Acinetobacter venetianus RAG-1 via RNA-seq with n-octacosane (C28) as the sole carbon source. Conserved sequence analysis revealed that it is a group III (Fe-containing/activated) ADH, which is widespread in the genus Acinetobacter. The deletion of adhA led to a significant reduction in the degradation of C28. AdhA exhibited optimal oxidative activity at pH 8.0 and 50 °C with NAD+ as coenzyme, while showing better tolerability to chemical reagents. Enzyme activity assay showed that AdhA owed the oxidative activity to a wide range of substrates including alkyl alcohols (C1-C32) and some isomeric alcohols, such as isopropanol, isobutanol, isoamyl alcohol, and propanetriol, and could reduce the alkyl aldehyde (C1-C12). Meanwhile, the binding of AdhA to different alkyl alcohols was mediated by different amino acids. AdhA is an ADH with an extremely broad substrate utilization range and excellent biochemical characteristics. These results provided important insights in the subsequent investigation of long-chain alkane degradation and petroleum pollution bioremediation.

Non-syntrophic Methanogenic Hydrocarbon Degradation by an Archaeal Species

Methanogenic hydrocarbon biodegradation alters the composition of many subsurface oil reservoirs (Jones et al. 2007). This process reduced the crude oil quality by removing alkanes and thus increasing the oil viscosity. The process has been described for syntrophic associations of hydrocarbon-degrading bacteria and methanogenic archaea (Zengler et al. 1999, Dolfing et al. 2007). However, recent culture-independent studies suggest that the archaeon ‘Candidatus Methanoliparum’ may combine alkane degradation and methanogenesis (Laso-Pérez et al. 2019, Borrel et al. 2019). Here we cultured Ca. Methanoliparum from a subsurface oil reservoir. To study this culture, situ hybridization, metagenomics and metatranscriptomics were combined with stable isotope probing and metabolite analyses for describing its functioning and assessing its potential role in reservoir chemistry. Incubated an anoxic oily sludge of the Shengli oilfield with sulfate-free medium, we established a methanogenic culture. This culture consumed various different long-chain alkanes, but also alkyl-benzenes and alkyl-cycloalkanes, and produced methane and CO2 as products (Fig. 1a-b). Our analyses revealed that our culture is dominated by a single archaeon, Ca. Methanoliparia (green). To study the specific turnover of n-alkanes, the cultures were supplemented with 1,2-13C-labelled or unlabelled n-hexadecane (Fig. 2). Within 100 days of incubation, both compounds were quantitatively converted into methane and carbon dioxide. In the 13C-labelling experiment, around 0.46 mmol of 13CH4 and around 0.15 mmol of 13CO2 were produced, which was equal to 85% to 92% of the stoichiometric conversion of the supplemented labelled hexadecane according to 4C16H34 + 30H2O -- 49CH4 + 15CO2 (Fig. 2a-d). We examined the functioning of Ca. Methanoliparum in the hexadecane-degrading culture using amplicon sequencing, metagenomics and metatranscriptomics. In the archaeal domain, the relative abundance of Ca. Methanoliparum in the hexadecane-degrading cultures comprised up to 75% of the total abundance according to analysis of archaeal 16S rRNA genes. Furthermore, Ca. Methanoliparum accounted for approximately 34–40% of the total microbial community as determined by metagenomic read recruitment estimation (Fig. 2e-f). We analysed the gene expression patterns of Ca. Methanoliparum during methanogenic hexadecane degradation (Fig. 3). The genes encoding the methanogenic hexadecane degradation pathway ranked among the top 10% to 25% of all Ca. M. thermophilum transcribed genes. Moreover, genes of Ca. M. thermophilum encoding ACR and MCR ranked among the top 2% of all transcribed genes within the whole community (Fig. 3b). The MAGs of Ca. M. thermophilum also showed the highest transcription among all described MAGs (Fig. 3c). These analyses indicate that Ca. M. thermophilum performs both the degradation of hexadecane and the formation of methane. We searched the cell extracts of the hexadecane-degrading cultures for hexadecyl-CoM formation using Q-Exactive Plus Orbitrap masss pectrometry. The unlabelled hexadecane culture contained a prominent mass peak of m/z = 365.21868 that matches the mass produced by synthesized authentic standard of hexadecyl-CoM. Fragmentation of both peaks yielded hexadecyl-thiol (m/z = 257.23080, C16H33S−), ethenesulfonate (m/z = 106.98074, C2H3SO3−) and bisulfite (m/z = 80.96510, HSO3−). Moreover, cultures supplied with 1,2-13C-hexadecane produced a peak at m/z = 367.22524 for 1,2-13C-hexadecyl-CoM and the fragment 259.23721 for 1,2-13C-hexadecyl-thiol, with a mass shift of 2 units compared with the unlabelled group. These analyses confirmed the activation of n-hexadecane as hexadecyl-CoM (Fig. 4). Here we demonstrate the activation of different hydrocarbon classes by ACRs of Ca. Methanoliparum, expanding the substrate range of this enzyme to an unforeseen number of compounds. Ca. Methanoliparum couples the degradation of long-chain alkanes and alkyl-substituted hydrocarbons to methane formation, proposed as alkylotrophy. Its metabolic pathways represent an additional mode of methanogenesis, adding to CO2 reduction, methylotrophy, methyl reduction, acetate fermentation and the recently reported methoxydotrophy. Ca. Methanoliparum grows in a wide temperature range, at least between 35 and 55 °C, covering the temperature range of most biodegraded oil reservoirs. Indeed, sequences of Ca. Methanoliparum are present in various anoxic hydrocarbon-rich environments worldwide. Thus, the demonstration of the unique features of Ca. Methanoliparum in hydrocarbon conversion may fundamentally change our view of crude oil transformation and biogeochemical processes in subsurface oil reservoirs. Future studies with Ca. Methanoliparia cultures will resolve the biochemical mechanisms of methanogenic hydrocarbon degradation in archaea, and will be helpful for the application of microbial-enhanced energyrecovery from depleted oil reservoirs.

Polystyrene-colonizing bacteria are enriched for long-chain alkane degradation pathways.

One of the most promising strategies for the management of plastic waste is microbial biodegradation, but efficient degraders for many types of plastics are still lacking, including those for polystyrene (PS). Genomics has emerged as a powerful tool for mining environmental microbes that may have the ability to degrade different types of plastics. In this study, we use 16S rRNA sequencing to analyze the microbiomes for multiple PS samples collected from sites with different vegetation in Taiwan to reveal potential common properties between species that exhibit growth advantages on PS surfaces. Phylum enrichment analysis identified Cyanobacteria and Deinococcus-Thermus as being the most over-represented groups on PS, and both phyla include species known to reside in extreme environments and could encode unique enzymes that grant them properties suitable for colonization on PS surfaces. Investigation of functional enrichment using reference genomes of PS-enriched species highlighted carbon metabolic pathways, especially those related to hydrocarbon degradation. This is corroborated by the finding that genes encoding long-chain alkane hydroxylases such as AlmA are more prevalent in the genomes of PS-associated bacteria. Our analyses illustrate how plastic in the environment support the colonization by different microbes compared to surrounding soil. In addition, our results point to the possibility that alkane hydroxylases could confer growth advantages of microbes on PS.

Degradation of long-chain alkanes through biofilm formation by bacteria isolated from oil-polluted soil

Three bacteria, Novosphingobium sp. S1, Gordonia amicalis S2 and Gordonia terrae S5, were isolated from a crude oil polluted soil and investigated for their ability to utilize long-chain alkanes (C16-C30). The strains were able to use n-hexadecane, n-octadecane and paraffins as carbon and energy source, although at different extents. Growth with alkanes, resulted in the formation of a biofilm at the alkane-water interface. Growth was shown to occur only if cells had access to the alkane-water interface suggesting that biofilm formation was required to assimilate these hydrophobic substrates. The interfacial access to alkanes is also supported by the ability of the strains to adhere to n-hexadecane, with Gordonia amicalis S2 and Gordonia terrae S5 exhibiting a much stronger adhesion than Novosphingobium sp. S1. None of the strains released biosurfactant into the culture medium which is consistent with an interfacial access to alkanes. LC-MS analyses revealed the release into the extracellular medium of 8-hydroxyhexadecanedioic acid by Novosphingobium sp. S1 and Gordonia amicalis S2, and 8-hydroxyhexadecanoic acid and 7-hydroxyhexadecanoic by Gordonia terrae S5. The production of these hydroxylated carboxylic acids substantiates the degradation of n-hexadecane by the strains although their physiological significance remains to be elucidated.

Identification of long-chain alkane-degrading (LadA) monooxygenases in Aspergillus flavus via in silico analysis.

Efficient degradation of alkanes in crude oil by the isolated Aspergillus flavus MM1 alluded to the presence of highly active alkane-degrading enzymes in this fungus. A long-chain alkane-degrading, LadA-like enzyme family in A. flavus was identified, and possible substrate-binding modes were analyzed using a computational approach. By analyzing publicly available protein databases, we identified six uncharacterized proteins in A. flavus NRRL 3357, of which five were identified as class LadAα and one as class LadAβ, which are eukaryotic homologs of bacterial long-chain alkane monooxygenase (LadA). Computational models of A. flavus LadAα homologs (Af1-Af5) showed overall structural similarity to the bacterial LadA and the unique sequence and structural elements that bind the cofactor Flavin mononucleotide (FMN). A receptor-cofactor-substrate docking protocol was established and validated to demonstrate the substrate binding in the A. flavus LadAα homologs. The modeled Af1, Af3, Af4, and Af5 captured long-chain n-alkanes inside the active pocket, above the bound FMN. Isoalloxazine ring of reduced FMN formed a π–alkyl interaction with the terminal carbon atom of captured alkanes, C16–C30, in Af3–Af5 and C16–C24 in Af1. Our results confirmed the ability of identified A. flavus LadAα monooxygenases to bind long-chain alkanes inside the active pocket. Hence A. flavus LadAα monooxygenases potentially initiate the degradation of long-chain alkanes by oxidizing bound long-chain alkanes into their corresponding alcohol.

Anaerobic Degradation of Alkanes by Marine Archaea.

Alkanes are saturated apolar hydrocarbons that range from their simplest form, methane, to high-molecular-weight compounds. Although alkanes were once considered biologically recalcitrant under anaerobic conditions, microbiological investigations have now identified several microbial taxa that can anaerobically degrade alkanes. Here we review recent discoveries in the anaerobic oxidation of alkanes with a specific focus on archaea that use specific methyl coenzyme M reductases to activate their substrates. Our understanding of the diversity of uncultured alkane-oxidizing archaea has expanded through the use of environmental metagenomics and enrichment cultures of syntrophic methane-, ethane-, propane-, and butane-oxidizing marine archaea with sulfate-reducing bacteria. A recently cultured group of archaea directly couples long-chain alkane degradation with methane formation, expanding the range of substrates used for methanogenesis. This article summarizes the rapidly growing knowledge of the diversity, physiology, and habitat distribution of alkane-degrading archaea.

Fast biodegradation of long-chain alkanes in heavily polluted soil by improving C/H conversion after pre-oxidation

This study aimed to explore the effects of Fenton pre-oxidation under different conditions on the indigenous bacterial communities and the mechanism of soil C/H conversion and rapid degradation of long-chain alkanes. The soil total petroleum hydrocarbons (TPH) content for this study was 27998 ± 883 mg/kg of soil. The results showed that the half-life period of the rapid long-chain degradation group was 266 days faster than that of the slow long-chain degradation group. After pre-oxidation, the number of bacteria in the fast group (5.07 log CFU/g) was higher than slow group (2.57 log CFU/g). Further studies showed that the consumption of ammonia nitrogen in the long-chain rapid degradation group was 1.37 times higher than that in the long-chain slow degradation group. The mapping characterization by DEEM revealed a high level of humic acid-like and organic matter produced by microbial metabolism in the fast group, and the long-chain degradation group had higher C/H conversion (35%), thus improving the degradation rate of long-chain alkanes (47%). High biomass and ammonia nitrogen consumption promoted higher C/H conversion. After proper pre-oxidation, the bacterial community changed, with an average relative abundance of 34% for Actinobacteria. This study has good engineering application value.

Degradation of long-chain n-alkanes by a novel thermal-tolerant Rhodococcus strain.

A novel bacterial strain, CH91, was isolated from a high-temperature oil reservoir. Morphological characterization, phylogenetic analyses of 16S rRNA gene sequence and genome relatedness indicated that the strain is a potential new species in the genus Rhodococcus. Strain CH91 could grow in the temperature range of 25-50°C (optimally at 37°C) and utilize a broad range of long-chain n-alkanes from hexadecane to hexatriacontane. The utilization of the n-alkanes mixture of strain CH91 revealed that the degradation rate was correlated to the length of the carbon chain. Two novel alkB genes encoding alkane 1-monooxygenase were found in the genome of this strain. The protein sequences of both alkane 1-monooxygenases showed a remarkable phylogenetic distance to other reported AlkB protein sequences. These results would help broaden our knowledge about alkane degradation by Rhodocuccus and its potential ecological role. The ability of the strain in the long-chain alkane degradation and thermal tolerance could also be further exploited for bioremediation of oil contaminations and microbial enhanced oil recovery.

Assessment of Hydrocarbon Degradation Potential in Microbial Communities in Arctic Sea Ice.

The anthropogenic release of oil hydrocarbons into the cold marine environment is an increasing concern due to the elevated usage of sea routes and the exploration of new oil drilling sites in Arctic areas. The aim of this study was to evaluate prokaryotic community structures and the genetic potential of hydrocarbon degradation in the metagenomes of seawater, sea ice, and crude oil encapsulating the sea ice of the Norwegian fjord, Ofotfjorden. Although the results indicated substantial differences between the structure of prokaryotic communities in seawater and sea ice, the crude oil encapsulating sea ice (SIO) showed increased abundances of many genera-containing hydrocarbon-degrading organisms, including Bermanella, Colwellia, and Glaciecola. Although the metagenome of seawater was rich in a variety of hydrocarbon degradation-related functional genes (HDGs) associated with the metabolism of n-alkanes, and mono- and polyaromatic hydrocarbons, most of the normalized gene counts were highest in the clean sea ice metagenome, whereas in SIO, these counts were the lowest. The long-chain alkane degradation gene almA was detected from all the studied metagenomes and its counts exceeded ladA and alkB counts in both sea ice metagenomes. In addition, almA was related to the most diverse group of prokaryotic genera. Almost all 18 good- and high-quality metagenome-assembled genomes (MAGs) had diverse HDGs profiles. The MAGs recovered from the SIO metagenome belonged to the abundant taxa, such as Glaciecola, Bermanella, and Rhodobacteracea, in this environment. The genera associated with HDGs were often previously known as hydrocarbon-degrading genera. However, a substantial number of new associations, either between already known hydrocarbon-degrading genera and new HDGs or between genera not known to contain hydrocarbon degraders and multiple HDGs, were found. The superimposition of the results of comparing HDG associations with taxonomy, the HDG profiles of MAGs, and the full genomes of organisms in the KEGG database suggest that the found relationships need further investigation and verification.

Degradation of Long-Chain Alkanes Through Biofilm Formation by Bacteria Isolated from Oil-Polluted Soil

Degradation of Long-Chain Alkanes Through Biofilm Formation by Bacteria Isolated from Oil-Polluted Soil

Non-syntrophic methanogenic hydrocarbon degradation by an archaeal species.

The methanogenic degradation of oil hydrocarbons can proceed through syntrophic partnerships of hydrocarbon-degrading bacteria and methanogenic archaea1-3. However, recent culture-independent studies have suggested that the archaeon 'Candidatus Methanoliparum' alone can combine the degradation of long-chain alkanes with methanogenesis4,5. Here we cultured Ca. Methanoliparum from a subsurface oil reservoir. Molecular analyses revealed that Ca. Methanoliparum contains and overexpresses genes encoding alkyl-coenzyme M reductases and methyl-coenzyme M reductases, the marker genes for archaeal multicarbon alkane and methane metabolism. Incubation experiments with different substrates and mass spectrometric detection of coenzyme-M-bound intermediates confirm that Ca. Methanoliparum thrives not only on a variety of long-chain alkanes, but also on n-alkylcyclohexanes and n-alkylbenzenes with long n-alkyl (C≥13) moieties. By contrast, short-chain alkanes (such as ethane to octane) or aromatics with short alkyl chains (C≤12) were not consumed. The wide distribution of Ca. Methanoliparum4-6 in oil-rich environments indicates that this alkylotrophic methanogen may have a crucial role in the transformation of hydrocarbons into methane.

Microbial degradation of n-hexadecane using Pseudomonas aeruginosa PU1 isolated from transformer-oil contaminated soil

The present work is carried out to determine the biodegradation potential of n-hexadecane by bacterial strain P. aeruginosa PU1 isolated from soil polluted with transformer oil. The bacteria showed its ability to grow in n-hexadecane containing medium and its utilization was revealed by a 2, 6-dichlorophenol indophenol assay, where complete decolorization of the medium occurred on the 5th day, at 35 °C. During the n-hexadecane degradation, maximum alkane hydroxylase (147 μmol min−1 mg−1) and alcohol dehydrogenase (113 μmol min−1 mg−1) activities were noticed at 3rd day of incubation. The production of such enzymes is important in the degradation of long-chain alkanes. On 10 days of incubation, P. aeruginosa PU1 degraded 100% n-hexadecane as performed by gravimetric analysis. The formation of P. aeruginosa PU1 biofilm in n-hexadecane containing medium was observed by the Scanning electron microscope (SEM) and intracellular accumulation of n-hexadecane was confirmed by Transmission electron microscope (TEM). Further, studies on ex-situ biodegradation results obtained from the Fourier transform infrared (FT-IR) and Gas Chromatography-Mass Spectrometer (GC-MS) analysis were interrelated with data obtained from Zeta Potential (ZP), Contact Angle (CA) measurement, and Gravimetric Analysis (GA) which showed the hydrophilic nature of the medium due to the production of acids and alcohol on the degradation of n-hexadecane. The biodegradation of the n-hexadecane resulted in the formation of products such as 3-pentyn-1-ol (C5H8O), n-hexyl formate (C7H14O2), cyclopentane propanoic acid (C8H14O2), and 2-ethylbutyl acrylate (C9H16O2). Based on morphological changes and end products formation upon degradation of n-hexadecane implies that the P. aeruginosa PU1 is a effective and robust model in degradation of n-hexadecane and strain can be utilized for reclamation of sites polluted with petroleum sources.

Aerated Static Pile (ASP) Enhanced Bioaugmentation of Oil Sludge Contaminated Soil Using LIBEM Consortium

This paper focused on efficiency of selective locally isolated beneficial microorganisms (LIBeM) consortia in bioaugmentation of oil sludge contaminated soil on a laboratory scale. Five different selective microbial consortia LIBeM were obtained from Environmental Microbiology Laboratory, Universiti Malaysia Sabah. The arrangement of aerated static pile (ASP)-bioreactor made up of acrylic materials was developed act as continuous aeration to the soil. Six different sets of treatment containing 10 kg of soil mixed with 20% (v/v) oil sludge with five bacterial strains and natural attenuation consisted of indigenous microbial in the soil as a control plot was utilized. The rates of biodegradation of oil sludge were studied for a period of three months and periodic sampling of soil from each bioreactor was carried out at 7 days of interval. Analysis of Total Petroleum Hydrocarbon (TPH) was done along with physiochemical parameters such as pH, moisture content and microbial population (CFUs) in the soil. The results obtained revealed biodegradation of oil sludge contaminated soil in all set treatments were much higher than Natural attenuation by 12.1 fold. The bioreactor augmented with Consortia 4 proved to be a better performance with 94% of TPH degradation followed by Consortia 2 (91.6%), Consortia 5 (90.1%), Consortia 1 (90%), Consortia 3 (87.5%) and Natural attenuation (27.4%) respectively. The variations of physiochemical parameters that influence the reduction of oil sludge in the soil were also discussed in this paper. High degradation of long chain alkanes was observed between consortia treatment as compared to natural attenuation plots suggested that bioaugmentation using consortia LIBeM decrease the level of oil sludge in contaminated soil. It was noted that, the continuous supplied of oxygen from aerated static pile (ASP)-system into the soil showed a good prospect in bioremediation of oil sludge.

Functional and Genomic Characterization of a Pseudomonas aeruginosa Strain Isolated From the Southwestern Gulf of Mexico Reveals an Enhanced Adaptation for Long-Chain Alkane Degradation

Indigenous bacterial populations play an important role in the restoration of crude oil-polluted marine environments. The identification and characterization of these bacteria are key in defining bioremediation strategies for the mitigation of possible future oil spills. In this work, we characterized Pseudomonas aeruginosa strain GOM1, which was isolated from the water column in the southwestern Gulf of Mexico. Phylogenetic analysis revealed that GOM1 strain was most closely related to P. aeruginosa WC55, a strain isolated from the northern Gulf of Mexico after the Deepwater Horizon oil spill. The hydrocarbon-degrading capacity of P. aeruginosa GOM1 was investigated using various approaches. This strain degraded 96% of the aliphatic fraction (C12-C38) of crude oil during a 30-day incubation period, exhibiting a high activity on long-chain alkanes, and expressing alkane hydroxylases AlkB1, AlkB2 and AlmA. Addition of nitrogen and phosphate to seawater culture medium enhanced hexadecane degradation by GOM1. Additionally, the strain exhibited high surfactant/rhamnolipid production and emulsifying activity when grown in a complex medium in the presence of hexadecane. Comparisons of growth kinetics, hydrocarbon degradation and gene expression between GOM1 and the closely related P. aeruginosa laboratory strain PAO1 revealed that the marine isolate is better adapted to degrade alkanes. Taken together, our results place P. aeruginosa GOM1 as a potentially effective candidate to be included in a consortium for use in the bioremediation of oil-polluted sites.

Survival and Energy Producing Strategies of Alkane Degraders Under Extreme Conditions and Their Biotechnological Potential.

Many petroleum-polluted areas are considered as extreme environments because of co-occurrence of low and high temperatures, high salt, and acidic and anaerobic conditions. Alkanes, which are major constituents of crude oils, can be degraded under extreme conditions, both aerobically and anaerobically by bacteria and archaea of different phyla. Alkane degraders possess exclusive metabolic pathways and survival strategies, which involve the use of protein and RNA chaperones, compatible solutes, biosurfactants, and exopolysaccharide production for self-protection during harsh environmental conditions such as oxidative and osmotic stress, and ionic nutrient-shortage. Recent findings suggest that the thermophilic sulfate-reducing archaeon Archaeoglobus fulgidus uses a novel alkylsuccinate synthase for long-chain alkane degradation, and the thermophilic Candidatus Syntrophoarchaeum butanivorans anaerobically oxidizes butane via alkyl-coenzyme M formation. In addition, gene expression data suggest that extremophiles produce energy via the glyoxylate shunt and the Pta-AckA pathway when grown on a diverse range of alkanes under stress conditions. Alkane degraders possess biotechnological potential for bioremediation because of their unusual characteristics. This review will provide genomic and molecular insights on alkane degraders under extreme conditions.

Effectiveness of Single and Microbial Consortium of Locally Isolated Beneficial Microorganisms (LIBeM) in Bioaugmentation of Oil Sludge Contaminated Soil at Different Concentration Levels: A Laboratory Scale

An aerated static pile ASP-bioreactor system made up of acrylic material dimension (60 cm × 40 cm × 20 cm) was developed to examine the potential of single and microbial consortium of LIBeM to remediate oil sludge contaminated soil at different concentration levels. Three different strains of LIBeM namely P. aeruginosa-BAS-Cr1, S. paucimobilis-ReTOS-Cr1 and S. maltophilia-RAS-Cr1 were used in this study was obtained from Environmental Microbiology Laboratory, Universiti Malaysia Sabah. Five sets of experiment filled with 10 kg of soils contaminated with 5% and 10% of oil sludge were carried out as Treatment 1 (contaminated soil+P. aeruginosa-BAS-Cr1), Treatment 2 (contaminated soil+S. paucimobilis-ReTOS-Cr1), Treatment 3 (contaminated soil+S. maltophilia-RASCr1), Treatment 4 (contaminated soil+Microbial Consortium; P. aeruginosa-BAS-Cr1+S. paucimobilis-ReTOSCr1+ S. maltophilia-RAS-Cr1) and Treatment 5 (contaminated soil+indigenous bacteria in soil; NA). Their ability to degrade hydrocarbon in the soil was investigated during 60 days incubation periods. Physical and chemical analyses were carried out from each of the treatment and control plot on a weekly basis to check for pH, moisture content, temperatures and Total Petroleum Hydrocarbon (TPH). The results showed that single strain P. aeruginosa- BAS-Cr1 has the highest oil degrading capacity compared to microbial consortium with 80% and 85.2% at both concentration studied. The percentage of TPH removal by P. aeruginosa-BAS-Cr1 is 3-fold higher than NA, thus confirmed that the addition of oil selective degrading bacteria was much better than the control plot. High degradation of long chain alkanes were observed between the control and treatment plot suggested that bioaugmentation using single and microbial consortium had decrease the level of oil sludge in contaminated soil.