Biodegradation of kerosene: Study of growth optimization and metabolic fate of P. janthinellum SDX7

Spectroscopic and Microscopic Characterization of Microbial Biofouling on Aircraft Fuel Tanks

Avoiding microbial contamination and biofilm formation on the surfaces of aircraft fuel tanks is a major challenge in the aviation industry. The inevitable presence of water in fuel systems and nutrients provided by the fuel makes an ideal environment for bacteria, fungi, and yeast to grow. Understanding how microbes grow on different fuel tank materials is the first step to control biofilm formation in aviation fuel systems. In this study, biofilms of Pseudomonas putida, a model Gram-negative bacterium previously found in aircraft fuel tanks, were characterized on aluminum 7075-T6 surfaces, which is an alloy used by the aviation industry due to favorable properties including high strength and fatigue resistance. Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray (EDX) showed that extracellular polymeric substances (EPS) produced by P. putida were important components of biofilms with a likely role in biofilm stability and adhesion to the surfaces. EDX analysis showed that the proportion of phosphorus with respect to nitrogen is higher in the EPS than in the bacterial cells. Additionally, different morphologies in biofilm formation were observed in the fuel phase compared to the water phase. Micro-Fourier transform infrared spectroscopy (micro-FTIR) analysis suggested that phosphoryl and carboxyl functional groups are fundamental for the irreversible attachment between the EPS of bacteria and the aluminum surface, by the formation of hydrogen bonds and inner-sphere complexes between the macromolecules and the aluminum surface. Based on the hypothesis that nucleic acids (particularly DNA) are an important component of EPS in P. putida biofilms, the impact of degrading extracellular DNA was tested. Treatment with the enzyme DNase I affected both water and fuel phase biofilms─with the cell structure disrupted in the aqueous phase, but cells remained attached to the aluminum coupons.

Exploring the bioremediation capability of petroleum-contaminated soils for enhanced environmental sustainability and minimization of ecotoxicological concerns

The bioremediation of soils contaminated with petroleum hydrocarbons (PHCs) has emerged as a promising approach, with its effectiveness contingent upon various types of PHCs, i.e., crude oil, diesel, gasoline, and other petroleum products. Strategies like genetically modified microorganisms, nanotechnology, and bioaugmentation hold potential for enhancing remediation of polycyclic aromatic hydrocarbon (PAH) contamination. The effectiveness of bioremediation relies on factors such as metabolite toxicity, microbial competition, and environmental conditions. Aerobic degradation involves enzymatic oxidative reactions, while bacterial anaerobic degradation employs reductive reactions with alternative electron acceptors. Algae employ monooxygenase and dioxygenase enzymes, breaking down PAHs through biodegradation and bioaccumulation, yielding hydroxylated and dihydroxylated intermediates. Fungi contribute via mycoremediation, using co-metabolism and monooxygenase enzymes to produce CO2 and oxidized products. Ligninolytic fungi transform PAHs into water-soluble compounds, while non-ligninolytic fungi oxidize PAHs into arene oxides and phenols. Certain fungi produce biosurfactants enhancing degradation of less soluble, high molecular-weight PAHs. Successful bioremediation offers sustainable solutions to mitigate petroleum spills and environmental impacts. Monitoring and assessing strategy effectiveness are vital for optimizing biodegradation in petroleum-contaminated soils. This review presents insights and challenges in bioremediation, focusing on arable land safety and ecotoxicological concerns.

Behavior of deteriogenic fungi in aviation fuels (fossil and biofuel) during simulated storage

Biofuels are expected to play a major role in reducing carbon emissions in the aviation sector globally. Farnesane ("2,6,10-trimethyldodecane") is a biofuel derived from the synthesized iso-paraffin route wich can be blended with jet fuel; however, the microbial behavior in farnesane/jet fuel blends remains unknown. The chemical and biological stability of blends should be investigated to ensure they meet the quality requirements for aviation fuels. This work aimed at evaluating the behavior of two fungi Hormoconis resinae (F089) and Exophiala phaeomuriformis (UFRGS Q4.2) in jet fuel, farnesane, and in 10% farnesane blend during simulated storage. Microcosms (150-mL flasks) were assembled with and without fungi containing Bushnell & Haas mineral medium for 28 days at a temperature of 20±2°C. The fungal growth (biomass), pH, surface tension, and changes in the fuel's hydrocarbon chains were evaluated. This study revealed thatthe treatment containing H. resinae showed a biomass of 19 mg, 12 mg, and 2 mg for jet fuel, blend, and farnesane respectively. The pH was reduced from 7.2 to 4.3 observed in jet fuel treatment The degradation results showed that compounds with carbon chains between C9 and C11, in jet fuel, and blend treatments were preferably degraded. The highest biomass (70.9 mg) produced by E. phaeomuriformis was in 10% farnesane blend, after 21 days. However, no significant decrease was observed on pH and surface tension measurements across the treatments as well as on the hydrocarbons when compared to the controls. This study revealed that farnesane neither inhibited nor promoted greater growth on both microorganisms.

Kerosene Biodegradation by Highly Efficient Indigenous Bacteria Isolated From Hydrocarbon-Contaminated Sites

Kerosene is widely used in Ethiopia as a household fuel (for lighting and heating), as a solvent in paint and grease, and as a lubricant in glass cutting. It causes environmental pollution and escorts to loss of ecological functioning and health problems. Therefore, this research was designed to isolate, identify, and characterize indigenous kerosene-degrading bacteria that are effective in cleaning ecological units that have been contaminated by kerosene. Soil samples were collected from hydrocarbon-contaminated sites (flower farms, garages, and old-aged asphalt roads) and spread-plated on mineral salt medium (Bushnell Hass Mineral Salts Agar Medium: BHMS), which consists of kerosene as the only carbon source. Seven kerosene-degrading bacterial species were isolated, 2 from flower farms, 3 from garage areas, and 2 from asphalt areas. Three genera from hydrocarbon-contaminated sites were identified, including Pseudomonas, Bacillus, and Acinetobacter using biochemical characterization and the Biolog database. Growth studies in the presence of various concentrations of kerosene (1% and 3% v/v) showed that the bacterial isolates could metabolize kerosene as energy and biomass. Thereby, a gravimetric study was performed on bacterial strains that proliferated well on a BHMS medium with kerosene. Remarkably, bacterial isolates were able to degrade 5% kerosene from 57.2% to 91% in 15 days. Moreover, 2 of the most potent isolates, AUG2 and AUG1, resulted in 85% and 91% kerosene degradation, respectively, when allowed to grow on a medium containing kerosene. In addition, 16S rRNA gene analysis indicated that strain AAUG1 belonged to Bacillus tequilensis, whereas isolate AAUG showed the highest similarity to Bacillus subtilis. Therefore, these indigenous bacterial isolates have the potential to be applied for kerosene removal from hydrocarbon-contaminated sites and the development of remediation approaches.

Effective degradation of Chlortetracycline using dual bio catalyst

Chlortetracycline (CTC) degradation using potential microbial consortia or individual bacterial strains was useful method for improving bioremediation potential. The co-culture (Klebsiella pneumoniae CH3 and Bacillus amyloliquefaciens CS1) of bacterial strains have the ability to degrade chlortetracycline (91.8 ± 1.7%), followed by sulfamethoxazole (62.1 ± 1.2%) and amoxicillin (73.9 ± 3.3%). It was observed that the degradation potential was maximum after 10 days incubation, 8-10% inoculum, pH 7.5, and antibiotic concentration ranged from 150 to 200 mg/L. The initial concentrations of CTC significantly affected CTC degradation. In strain CH3, maximum biodegradation of CTC (99.4 ± 2.3%) was observed at 200 mg/L initial CTC concentrations. In CS1, maximum biodegradation of CTC was obtained at 150 mg/L concentration (80.5 ± 3.2%) after 10 days of culture. Alkaline pH was found to be suitable for the degradation of antibiotic than acidic range. After initial optimization by one factor at a time approach in free cells, the bacterial strains (CH3 and CS1) were co-immobilized. The co-immobilized bacterial cells showed improved degradation potential than free cells. To determine the biodegradation potential of immobilized cells, the selected strains were immobilized in polymer beads and treated with CTC with 175 mg/L initial concentration. The experimental results revealed that after 3 days of treatment the residual CTC concentration was 150.1 ± 3.2 mg/L and it decreased as 1.28 ± 0.01 mg/L after 10 days of treatment. The present study confirmed the effectiveness and feasibility of biodegradation ability of K. pneumoniae CH3 and B. amyloliquefaciens CS1 immobilized for CTC degradation in wastewater.

Biodegradation of phenol by a halotolerant versatile yeast Candida tropicalis SDP-1 in wastewater and soil under high salinity conditions

In this study, a novel halotolerant phenol-degrading yeast strain, SDP-1, was isolated from a coastal soil in Jiangsu, China, and identified as Candida tropicalis by morphology and rRNA internal transcribed space region sequence analysis. Strain SDP-1 can efficiently remove phenol at wide ranges of pH (3.0-9.0), temperature (20-40 °C), and NaCl (0-5%, w/v), as well as the tolerance of Mn²⁺, Zn²⁺ and Cr³⁺ in aquatic phase. It also utilized multiple phenol derivatives and aromatic hydrocarbons as sole carbon source and energy for growth. Free cells of SDP-1 were able to degrade the maximum phenol concentration of 1800 mg/L within 56 h under the optimum culture conditions of 10% inoculum volume, pH 8.0, 35 °C and 200 rpm agitation speed. Meanwhile, SDP-1 was immobilized on sodium alginate, and the capability of efficiently phenol degradation of free cells and immobilized SDP-1 were evaluated. Shortened degradation time and long-term utilization and recycling for immobilized SDP-1 was achieved compared to free cells. The 1200 mg/L of phenol under 5% NaCl stress could be completely degraded within 40 h by immobilized cells. In actual industrial coking wastewater, immobilized cells were able to completely remove 383 mg/L phenol within 20 h, and the corresponding chemical oxygen demand (COD) value was decreased by 50.38%. Besides, in phenol-contained salinity soil (3% NaCl), 100% of phenol (500 and 1000 mg/kg) removal efficiency was achieved by immobilized SDP-1 within 12 and 26 days, respectively. Our study suggested that versatile yeast Candida tropicalis SDP-1 could be potentially used for enhanced treatment of phenol-contaminated wastewater and soil under hypersaline or no-salt environmental conditions.

Effective degradation of tetracycline by manganese peroxidase producing Bacillus velezensis strain Al-Dhabi 140 from Saudi Arabia using fibrous-bed reactor

A tetracycline degrading bacterial strains was characterized from the municipal sludge and detected its ability to produce manganese peroxidase. The molecular weight of manganese peroxidase was determined as 46 kDa after Biogel P-100 gel filtration column chromatography purification. Maximum tetracycline degradation was observed with the manganese peroxidase from the strain Bacillus velezensis Al-Dhabi 140 and the optimum degradation process was studied. Optimization revealed the maximum removal efficacy was obtained as 87 mg/L at initial tetracycline concentration 143.75 mg/L, pH 6.94 and 8.04% inoculum. Consequently, fibrous bed reactor containing the culture of B. velezensis Al-Dhabi 140 in fibrous matrix was formed to transform tetracycline in synthetic wastewater. The transformed product of tetracycline from the fibrous bed reactor was evident by the activity of ligninolytic enzymes produced by B. velezensis Al-Dhabi 140 in reactor. The decreased level of antibacterial potency was obtained after 10 days. The zone of inhibition was 24 ± 1 mm after 1 day and it decreased as 9 ± 1 mm after 10 days. Based on the findings, fibrous bed B. velezensis Al-Dhabi 140 could be an efficient strain for tetracycline removal from artificial wastewater, even from natural wastewater.

Biodegradation of gentamicin by bacterial consortia AMQD4 in synthetic medium and raw gentamicin sewage

Gentamicin, a broad spectrum antibiotic of the aminoglycoside class, is widely used for disease prevention of human beings as well as animals. Nowadays the environmental issue caused by the disposal of wastes containing gentamicin attracts increasing attention. In this study, a gentamicin degrading bacterial consortia named AMQD4, including Providencia vermicola, Brevundimonas diminuta, Alcaligenes sp. and Acinetobacter, was isolated from biosolids produced during gentamicin production for the removal of gentamicin in the environment. The component and structure of gentamicin have a great influence on its degradation and gentamicin C1a and gentamicin C2a were more prone to being degraded. AMQD4 could maintain relatively high gentamicin removal efficiency under a wide range of pH, especially in an alkaline condition. In addition, AMQD4 could remove 56.8% and 47.7% of gentamicin in unsterilized and sterilized sewage in a lab-scale experiment, respectively. And among the isolates in AMQD4, Brevundimonas diminuta BZC3 performed the highest gentamicin degradation about 50%. It was speculated that aac3iia was the gentamicin degradation gene and the main degradation product was 3'-acetylgentamicin. Our results suggest that AMQD4 and Brevundimonas diminuta BZC3 could be important candidates to the list of superior microbes for bioremediation of antibiotic pollution.

Gentamicin removal in submerged fermentation using the novel fungal strain Aspergillus terreus FZC3

Social concern and awareness of the potential risk posed by environmental residues of antibiotics such as gentamicin in the development of antibiotic resistance genes have increased. The present study used laboratory-scale experiments to develop methods for gentamicin removal from the environment. A fungus, strain FZC3, which could remove gentamicin in submerged fermentation, was isolated from solid waste and sewage water from a gentamicin production factory. The fungus was identified as Aspergillus terreus by sequencing the PCR-amplified ITS fragments of its rRNA-coding genes and by its morphology. The gentamicin removal efficiency exceeded 95% by day 7 under optimized culture conditions. The results showed that both biosorption and biodegradation were involved. We speculated that Aspergillus terreus FZC3 absorbed gentamicin and subsequently degraded it. We also found that Aspergillus terreus FZC3 survived and maintained a high bioremediation efficiency over a wide pH range, indicating its potential for future use in the large-scale bioremediation of gentamicin.