Characterization of crude oil degrading bacterial communities and their impact on biofilm formation

Sustainable Biofilm Inhibition Using Chitosan-Mesoporous Nanoparticle-Based Hybrid Slippery Composites

In recent decades, extensive research has been directed toward mitigating microbial contamination and preventing biofilm formation. However, many conventional antibiofilm methods rely on hazardous and toxic substances, neglecting potential risks to human health and the environment. Moreover, these approaches often rely on single-strategy mechanisms, utilizing either bactericidal or fouling-resistant agents, which have shown limited efficacy in long-term biofilm suppression. In this study, we propose an efficient and sustainable biofilm-resistant slippery hybrid slippery composite. This composite integrates nontoxic and environmentally friendly materials including chitosan, silicone oil-infused polydimethylsiloxane, and mesoporous silica nanoparticles in a synergistic manner. Leveraging the bacteria-killing properties of chitosan and the antifouling capabilities of the silicone oil layer, the hybrid composite exhibits robust antibiofilm performance against both Gram-positive and Gram-negative bacteria. Furthermore, the inclusion of mesoporous silica nanoparticles enhances the oil absorption capacity and self-replenishing properties, ensuring exceptional biofilm inhibition even under harsh conditions such as exposure to high shear flow and prolonged incubation (7 days). This approach offers promising prospects for developing effective biofilm-resistant materials with a reduced environmental impact and improved long-term performance.

Impact of artisanal refining activities on bacterial diversity in a Niger Delta fallow land

Hydrocarbon pollution is a major ecological problem facing oil-producing countries, especially in the Niger Delta region of Nigeria. In this study, a site that had been previously polluted by artisanal refining activity was investigated using 16S rRNA Illumina high-throughput sequencing technology and bioinformatics tools. These were used to investigate the bacterial diversity in soil with varying degrees of contamination, determined with a gas chromatography-flame ionization detector (GC-FID). Soil samples were collected from a heavily polluted (HP), mildly polluted (MP), and unpolluted (control sample, CS) portion of the study site. DNA was extracted using the Zymo Research (ZR) Fungi/Bacteria DNA MiniPrep kit, followed by PCR amplification and agarose gel electrophoresis. The microbiome was characterized based on the V3 and V4 hypervariable regions of the 16S rRNA gene. QIIME (Quantitative Insights Into Microbial Ecology) 2 software was used to analyse the sequence data. The final data set covered 20,640 demultiplexed high-quality reads and a total of 160 filtered bacterial OTUs. Proteobacteria dominated samples HP and CS, while Actinobacteria dominated sample MP. Denitratisoma, Pseudorhodoplanes, and Spirilospora were the leading genera in samples HP, CS, and MP respectively. Diversity analysis indicated that CS [with 25.98 ppm of total petroleum hydrocarbon (TPH)] is more diverse than HP (with 490,630 ppm of TPH) and MP (with 5398 ppm of TPH). A functional prediction study revealed that six functional modules dominated the dataset, with metabolism covering up to 70%, and 11 metabolic pathways. This study demonstrates that a higher hydrocarbon concentration in soil adversely impacts microbial diversity, creating a narrow bacterial diversity dominated by hydrocarbon-degrading species, in addition to the obvious land and ecosystem degradation caused by artisanal refining activities. Overall, the artisanal refining business is significantly driving ecosystem services losses in the Niger Delta, which calls for urgent intervention, with focus on bioremediation.

Impact of biosurfactant produced by Bacillus spp. on biodegradation efficiency of crude oil and anthracene

Biosurfactants are surface active molecules generated by various microorganisms, including bacteria, actinobacteria, algae, and fungi. In this study, bacterial strains are isolated from soil contaminated with used motor oil and examined for potential biosurfactant production. A minimum salt medium (MSM), with crude oil as the only carbon source, is used to isolate potential biosurfactant-producing bacterial strains. About 23 strains are isolated, and all are subjected to the primary screening methods for biosurfactant production. Based on the emulsification index, oil displacement, and drop collapse screening methods, two isolates with potential biosurfactant-producing ability are selected for further studies. The synthesis of biosurfactants, crude oil and anthracene biodegradation is carried out with strains DTS1 and DTS2. Both strains show significant outcomes in crude oil degradation. In addition, both strains can utilize anthracene as the sole carbon source. During the degradation course, changes in the growth conditions are continuously monitored by measuring turbidity and pH. In this degradation study, the biosurfactant production aptitude of the isolated strains plays an essential role in increasing the bioavailability of hydrophobic hydrocarbons. These strains are identified down to the molecular level by employing 16S rRNA gene sequencing, and the acquired sequences are submitted to get the accession numbers. These prospective strains can be utilized to remediate hydrocarbon-contaminated environments.

Enrichment of microbial consortia for MEOR in crude oil phase of reservoir-produced liquid and their response to environmental disturbance

Developing microbial consortiums is necessary for microbial enhanced oil recovery (MEOR) in heavy crude oil production. The aqueous phase of produced fluid has long been considered an ideal source of microorganisms for MEOR. However, it is recently found that rich microorganisms (including hydrocarbon-degrading bacteria) are present in the crude oil phase, which is completely different from the aqueous phase of produced fluid. So, in this study, the microbial consortia from the crude oil phase of produced fluids derived from four wells were enriched, respectively. The microbial community structure during passage was dynamically tracked, and the response of enriched consortia to successive disturbance of environmental factors was investigated. The results showed the crude oil phase had high microbial diversity, and the original microbial community structure from four wells was significantly different. After ten generations of consecutive enrichment, different genera were observed in the four enriched microbial consortia, namely, Geobacillus, Bacillus, Brevibacillus, Chelativorans, Ureibacillus, and Ornithinicoccus. In addition, two enriched consortia (eG1614 and eP30) exhibited robustness to temperature and oxygen perturbations. These results further suggested that the crude oil phase of produced fluids can serve as a potential microbial source for MEOR.

Dibenzothiophene removal by environmental bacteria with differential accumulation of intracellular inorganic polyphosphate

Dibenzothiophene (DBT), which belongs to the group of polycyclic aromatic heterocycles of sulfur, is a model substance to study the removal of sulfur compounds from oil due to its recalcitrance to traditional and specific removal processes. The aim of this work was to evaluate DBT bioremoval by environmental bacteria and its relationship with polyphosphate (polyP) accumulation, cell surface characteristics and bioemulsifying activity. Pseudomonas sp. P26 achieved the highest DBT removal percentage (48%) after 7 days of incubation. Moreover, positive correlations were estimated between DBT removal and bioemulsifying activity and biofilm formation. A strain-dependent relationship between the content of intracellular polyP and the presence of DBT in the culture medium was also demonstrated. The study of these bacterial characteristics, which could promote DBT transformation, is a first approach to select DBT-removing bacteria, in order to develop bioformulations that are able to contribute to desulfurization processes of petroleum-derived pollutants in the future.

Highly efficient screening and optimal combination of functional isolates for bioremediation of hydrocarbon-polluted soil

The key to enhancing the efficacy of bioremediation of hydrocarbon-contaminated soil is the precise and highly efficient screening of functional isolates. Low screening effectiveness, narrow screening range and an unstable structure of the constructed microflora during bioremediation are the shortcomings of the traditional shaking culture (TSC) method. To improve the secondary screening of isolates and microflora implemented for alkane degradation, this work evaluated the characterization relationship between bacterial function and enzyme activity and devised an enzyme activity assay (EAA) method. The results indicated a substantial positive correlation (r = 0.97) between 24 candidate isolates and their whole enzymes, proving that whole enzyme activity properly reflects the metabolic functions of microorganisms. The functional analysis of the isolates demonstrated that the EAA method in conjunction with microbial abundance and metabolite determination could broaden the screening range of functional isolates, including aliphatic acid-metabolizing isolates (isolates H4 and H7) and aliphatic acid-sensitive isolates (isolate H2) with n-hexadecane degradation ability. The EAA method also guided the construction of functional microflora and optimized the mode of application using combinations of alkane-degrading bacteria and aliphatic acid-degrading bacteria successively (e.g., F1+H7+H7). The combinations maintained a high abundance of functional isolates and stable α diversity and community composition throughout the experiment, which contributed to more advanced alkane degradation and mineralization ability (p < 0.01). Assuming a workload of 100 tests, the screening efficiency of the EAA method is more than 16 times that of the TSC method, and the greater the quantity of isolates, the higher the screening efficiency, enabling high-throughput screening. In conclusion, the EAA method has a broad-spectrum, accurate and highly efficient screening ability for functional isolates and microflora, which can provide intensive technical support for the development of bioremediation materials and the application of bioremediation technology.

Effects of co-modified biochar immobilized laccase on remediation and bacterial community of PAHs-contaminated soil

Considering the stability and economy of immobilized enzymes, this study prepared co-modified biochar immobilized laccase product named Fe₃O₄@NaBC@GA@LC via orthogonal experimental design and explored its possibility of remediating polycyclic aromatic hydrocarbons (PAHs) contaminated soil in steel plants. Compared with the free laccase treatment, the relative activity of Fe₃O₄@NaBC@GA@LC remained 60 % after 50 days of incubation at room temperature. The relative activity of Fe₃O₄@NaBC@GA@LC could still retain nearly 80 % after five reuses. In the process of simulating the PAHs-contaminated site treatment experiment in Hangzhou Iron and steel plant, immobilized laccase exhibited efficient adsorption and degradation performances and even the removal rate of 5-ring PAHs reached more than 90 % in 40 days, resulting in improving urease activity and dehydrogenase in the soil and promoted the growth of a PAH degrading bacteria (Massilia). Our results further explained the efficient degradation effects of Fe₃O₄@NaBC@GA@LC on PAHs, which make it a promising candidate for PAHs-contaminated soil remediation.

Metagenomics diversity analysis of sulfate-reducing bacteria and their impact on biocorrosion and mitigation approach using an organometallic inhibitor

Sulfate-reducing bacteria (SRB) have impacted the biocorrosion process for various industrial sectors, especially in the oil and gas industry. The higher stability over extreme conditions is the key parameter for their survival in such environments. So far, many materials have been tried to minimize or control the growth of SRB. In the present study, an organo-metallic compound of the zinc sorbate (ZS) was successfully synthesized by the simple co-precipitation method and its improved antibacterial activity against SRB. The SRB consortia are enriched from the sub-surface soil sample and identified by 16s rDNA sequencing by targeting the V3-V4 region. The most dominating genera identified with sulfate-reducing capability are Sulfurospirillum (42 %), Shewanella (19 %) Bacteroides (14 %), and Desulfovibrio (8 %). Further biocorrosion experiments are conducted by weight loss methods. Higher corrosion current density (I_corr) and less charge transfer resistance (R_ct) are observed for the SRB consortia. Concurrently, higher R_ct is kept for the inhibitor-included systems. The slowest release of the sorbate into the medium suppressed the growth of the SRB bacterial cells with 86 ± 3 % corrosion inhibition efficiency and prevented further corrosion reactions by forming a protective layer over the surface of the carbon steel API 5LX. The surface analysis strongly confirmed that SRB caused pitting corrosion, which has been suppressed in the inhibitor-included systems.

Study on the Effect of Petroleum Components on the Elution of Oily Sludge by a Compound Biosurfactant

Currently, research on oily sludge treatment mainly focuses on optimizing the deoiling effect and research on the deoiling mechanism, and the influence of petroleum components on the properties and treatment of oily sludge is rarely considered. Therefore, in this study, petroleum substances in three types of oil sludge were eluted using the biosurfactant cleaning technology, and the influence of petroleum components on the cleaning process was explored. The results showed that the biosurfactants rhamnolipid and sophorolipid had a synergistic effect, and the oil-removal rate was as high as 92.2% when the SL mass fraction was 0.4 in the compound biosurfactant. Three types of oily sludge, wellsite-landing sludge, pipeline-landing sludge, and tank-bottom sludge, were cleaned by the compound biosurfactant; the results showed that the residual petroleum substance in liquid and solid phases, the turbidity value, and the zeta-potential value of the supernatant of oil sludge samples after cleaning increased with the increase in the heavy components of the oily sludge, and the oil-removal rate decreased gradually. After cleaning, the average relative molecular weight of the three oil phases increased with the heavy components, which was increased by 1.83, 4.83, and 10.72%, respectively, and the increase in molecular weight increased the difficulty of cleaning. After cleaning, the retention time and peak intensity of the oil sample changed significantly, and it had a stronger elution effect on low-molecular-weight alkanes. It was found that the compound biosurfactant had a good elution effect on polycyclic aromatic hydrocarbons, but the increase in the content of heavy components and the increase in aromatic rings increased the difficulty of cleaning. Moreover, it was found that the compound biosurfactant could not completely elute the petroleum substances on the surface of solid particles, and the asphaltene components in the oil phase were more difficult to elute than other components.

Biofilm formation on copper and its control by inhibitor/biocide in cooling water environment

The present study has successfully identified the nitrate reducing bacteria present in the cooling water system and also investigated the performance of industrially applied biocide and inhibitor on the bacterial inhibition. In order to carry out the objective of this study, facilities and methods such as 16S rRNA gene sequencing, Lowry assay, SEM, EIS, ICP-MS and weight loss analysis were being utilized. In this study, two out of the five morphologically dis- similar colonies identified through 16S rRNA gene sequencing, namely the Massilia timonae and the Pseudomonas, were being utilized in the biocorrosion study on copper metal. From the surface analysis using SEM demonstrated the phenomenon of biofilm formation on the copper surface. 2-methylbenzimidazole has the addition of methyl group in the diazole ring position of benzimidazole it has create basicity environment and inhibit the metal deterioration. Meanwhile, it is also deducible from the EIS and protein analysis that com- bination of biocide with either of the inhibitors gives rise to better biocorrosion suppression (0.00178 mpy and 0.00171mpy) as compared to the sole effect of either biocide or inhibitor (0.00219 mpy, 0.00162 and 0.00143). Biocorrosion system biocide with MBM was found to exhibit 65% corrosion inhibition efficiency. Moreover, adoption of 2-Methylbenzimidazole seems to display better performance as compared to Multionic 8151, which is adopted in cooling water system.

The impact of bacterial diversity on resistance to biocides in oilfields

Extreme conditions and the availability of determinate substrates in oil fields promote the growth of a specific microbiome. Sulfate-reducing bacteria (SRB) and acid-producing bacteria (APB) are usually found in these places and can harm important processes due to increases in corrosion rates, biofouling and reservoir biosouring. Biocides such as glutaraldehyde, dibromo-nitrilopropionamide (DBNPA), tetrakis (hydroxymethyl) phosphonium sulfate (THPS) and alkyl dimethyl benzyl ammonium chloride (ADBAC) are commonly used in oil fields to mitigate uncontrolled microbial growth. The aim of this work was to evaluate the differences among microbiome compositions and their resistance to standard biocides in four different Brazilian produced water samples, two from a Southeast Brazil offshore oil field and two from different Northeast Brazil onshore oil fields. Microbiome evaluations were carried out through 16S rRNA amplicon sequencing. To evaluate the biocidal resistance, the Minimum Inhibitory Concentration (MIC) of the standard biocides were analyzed using enriched consortia of SRB and APB from the produced water samples. The data showed important differences in terms of taxonomy but similar functional characterization, indicating the high diversity of the microbiomes. The APB and SRB consortia demonstrated varying resistance levels against the biocides. These results will help to customize biocidal treatments in oil fields.

Enhanced biodegradation of hydrophobic organic pollutants by the bacterial consortium: Impact of enzymes and biosurfactants

Hydrocarbons and their derivative compounds are recalcitrant in nature and causing adverse impacts to the environment and are classified as important pollutants. Removal of these pollutants from the atmosphere is a challenging process. Hydrophobic organic pollutants (HOPs) including crude oil, diesel, dotriacontane (C₃₂), and tetracontane (C₄₀) are subjected to the biodegradation study by using a bacterial consortium consist of Bacillus subtilis, Pseudomonas stutzeri, and Acinetobacter baumannii. The impact of pH and temperature on the biodegradation process was monitored. During the HOPs biodegradation, the impact of hydrocarbon-degrading extracellular enzymes such as alcohol dehydrogenase, alkane hydroxylase, and lipase was examined, and found average activity about 47.2, 44.3, and 51.8 μmol/mg^-1, respectively. Additionally, other enzymes such as catechol 1,2 dioxygenase and catechol 2,3 dioxygenase were found as 118 and 112 μmol/mg^-1 Enzyme as an average range in all the HOPs degradation, respectively. Also, the impact of the extracellular polymeric substance and proteins were elucidated during the biodegradation of HOPs with the average range of 116.90, 54.98 mg/L^-1 respectively. The impact of biosurfactants on the degradation of different types of HOPs is elucidated. Very slight changes in the pH were also noticed during the biodegradation study. Biodegradation efficiency was calculated as 90, 84, 76, and 72% for crude oil, diesel, C_32, and C₄₀, respectively. Changes in the major functional groups (CH, C-O-C, CO, =CH₂, CH₂, CH₃) were confirmed by FTIR analysis and intermediated metabolites were identified by GCMS analysis. The surface-active molecules along with the enzymes played a crucial role in the biodegradation process.