Biodegradation of methyl tert-butyl ether by cometabolism with hexane in biofilters inoculated with Pseudomonas aeruginosa

Thermal and structural changes of a starch flexible film and cellulosic semi-rigid tray during the biodegradation process under controlled composting conditions

Biopolymers used to mitigate the environmental impact needed establish biodegradation percentage. The thermal and structural changes of two plastic materials, a flexible film based on cassava starch - Poly(lactic acid) (PLA) and a semi-rigid cassava flour-stay cellulose fique fiber, were evaluated biodegradation under ISO 4855-1 standard. The tests were carried out for four weeks at constant temperature and flow of 58 °C ± 2 °C and 250 mL/h, using a mature compost as inoculum. The percentages of CO2, thermal, morphological, and structural changes, variation of degradation temperatures, glass transition temperatures (Tg), Melting temperatures (Tm) and enthalpies of fusion (Hm), were properly evaluated as indicators of the materials biodegradation of two materials. Scanning electron microscopy (SEM), showed the microorganisms colonization on the materials surface, evidencing the appearance of cracks and microbial population. The flexible film showed a biodegradation percentage of 98.24 %, the semi-rigid tray 89.06 %, and the microcrystalline cellulose, 81.37 %.

Pilot-scale biofiltration of 1,4-dioxane at drinking water-relevant concentrations

1,4-Dioxane is a drinking water contaminant of emerging concern. Because conventional and many advanced drinking water treatment technologies are ineffective for 1,4-dioxane removal, cost-effective technologies for the removal of 1,4-dioxane at drinking water-relevant concentrations are needed. In this research, a gravity-fed, cometabolic biofiltration system was developed to degrade 1,4-dioxane that was spiked into coagulated, settled surface water at a concentration of ∼10 µg/L. Objectives were to determine whether cometabolic degradation of trace levels of 1,4-dioxane can be sustained using n-butane as primary substrate and whether filter media properties and empty bed contact time (EBCT) affect biofiltration efficiency. A mixed culture of bacteria derived from the Cape Fear River basin and previously enriched using isobutane served as inoculum for biologically active filters. Two granular activated carbons (GACs) with different grain sizes and one carbonaceous resin were used as attachment media, and n-butane served as the primary substrate for biologically active filters. Non-inoculated controls with the same media were evaluated in parallel to distinguish between biological and adsorptive removals of 1,4-dioxane. For the duration of the pilot study (>3 months), 1,4-dioxane was degraded in inoculated biofilters receiving n-butane. In control filters containing larger and smaller grain GAC, 1,4-dioxane broke through completely within 750 and 1250 bed volumes, respectively, corresponding to 15 to 30 days of operation at an EBCT of 30 min. 1,4-Dioxane removal increased with increasing EBCT in all biologically active filters. At an EBCT of 30 min, the biologically active GAC filter containing the larger-grain GAC removed on average 87% of 1,4-dioxane at pseudo steady-state. When the hydraulic loading rate was decreased to achieve an overall EBCT of 60 min, 1,4-dioxane was removed to <1 µg/L in the biologically active GAC filter containing the larger-grain GAC. Activity-based labeling showed the presence of catalytically active monooxygenases in backwash water from biologically active filters that degraded 1,4-dioxane. Amplicon sequencing results showed that while taxa shifted after the initial inoculation of biologically active filters, taxa in biologically active filters remained more similar to the inoculum than those in the non-inoculated control filters. Overall, results of this research demonstrate that cometabolic degradation of 1,4-dioxane at trace levels is possible for extended periods of time in inoculated biofilters that receive n-butane as primary substrate.

Characterization of co-metabolic biodegradation of methyl tert-butyl ether by a Acinetobacter sp. strain

Co-metabolic bioremediation is a promising approach for the elimination of methyl tert-butyl ether (MTBE), which is a common pollutant found worldwide in ground water. In this paper, a bacterial strain able to co-metabolically degrade MTBE was isolated and named as Acinetobacter sp. SL3 based on 16S rRNA gene sequencing analysis. Strain SL3 could grow on n-alkanes (C₅–C₈) accompanied with the co-metabolic degradation of MTBE. The number of carbons present in the n-alkane substrate significantly influenced the degradation rate of MTBE and accumulation of tert-butyl alcohol (TBA), with n-octane resulting in a higher MTBE degradation rate (V_max = 36.7 nmol min⁻¹ mg_protein⁻¹, K_s = 6.4 mmol L⁻¹) and lower TBA accumulation rate. A degradation experiment in a fed-batch reactor revealed that the efficiency of MTBE degradation by Acinetobacter sp. strain SL3 did not show an obvious decrease after nine rounds of MTBE replenishment ranging from 0.1–0.5 mmol L⁻¹. The results of this paper reveal the preferable properties of Acinetobacter sp. SL3 for the bioremediation of MTBE via co-metabolism and leads towards the development of new MTBE elimination technologies.

Acinetobacter sp. SL3 could co-metabolically degrade MTBE when grown on n-alkanes. An extremely low TBA accumulation were achieved on n-octane. The fed-batch reactor degradation revealed continuous MTBE degradation capacity by Acinetobacter sp. SL3.

Polypyrrole-Grafted Coconut Shell Biological Carbon as a Potential Adsorbent for Methyl Tert-Butyl Ether Removal: Characterization and Adsorption Capability

Methyl tert-butyl ether (MTBE) has been used as a common gasoline additive worldwide since the late twentieth century, and it has become the most frequently detected groundwater pollutant in many countries. This study aimed to synthesize a novel microbial carrier to improve its adsorptive capacity for MTBE and biofilm formation, compared to the traditional granular activated carbon (GAC). A polypyrrole (PPy)-modified GAC composite (PPy/GAC) was synthesized, and characterized by Fourier transform infrared spectroscopy (FT-IR) and Brunauer-Emmett-Teller (BET) surface area analysis. The adsorption behaviors of MTBE were well described by the pseudo-second-order and Langmuir isotherm models. Furthermore, three biofilm reactors were established with PPy/GAC, PPy, and GAC as the carriers, respectively, and the degradation of MTBE under continuous flow was investigated. Compared to the biofilm reactors with PPy or GAC (which both broke after a period of operation), the PPy/GAC biofilm column produced stable effluents under variable treatment conditions with a long-term effluent MTBE concentration <20 μg/L. Pseudomonas aeruginosa and Acinetobacter pittii may be the predominant bacteria responsible for MTBE degradation in these biofilm reactors.

Biodegradation of Methyl tert-Butyl Ether by Co-Metabolism with a Pseudomonas sp. Strain

Co-metabolic bioremediation is supposed to be an impressive and promising approach in the elimination technology of methyl tert-butyl ether (MTBE), which was found to be a common pollutant worldwide in the ground or underground water in recent years. In this paper, bacterial strain DZ13 (which can co-metabolically degrade MTBE) was isolated and named as Pseudomonas sp. DZ13 based on the result of 16S rRNA gene sequencing analysis. Strain DZ13 could grow on n-alkanes (C₅-C₈), accompanied with the co-metabolic degradation of MTBE. Diverse n-alkanes with different carbon number showed a significant influence on the degradation rate of MTBE and accumulation of tert-butyl alcohol (TBA). When Pseudomonas sp. DZ13 co-metabolically degraded MTBE with n-pentane as the growth substrate, a higher MTBE-degrading rate (V_max = 38.1 nmol/min/mg_protein, K_s = 6.8 mmol/L) and lower TBA-accumulation was observed. In the continuous degradation experiment, the removal efficiency of MTBE by Pseudomonas sp. Strain DZ13 did not show an obvious decrease after five times of continuous addition.

Cometabolism of methyl tert-butyl ether by a new microbial consortium ERS

The release of methyl tert-butyl-ether (MTBE) into the environment has increased the worldwide concern about the pollution of MTBE. In this paper, a microbial consortium was isolated from the soil sample near an oil station, which can degrade MTBE directly with a low biomass yield and MTBE degrading efficiency. Further research has indicated that this consortium can degrade MTBE efficiently when grown on n-octane as the cometabolic substrate. The results of 16S rDNA based on phylogenetic analysis of the selected operating taxonomic units (OTUs) involved in the consortium revealed that one OTU was related to Pseudomonas putida GPo1, which could cometabolically degrade MTBE on the growth of n-octane. This may help explain why n-octane could be the optimal cometabolic substrate of the consortium for MTBE degradation. Furthermore, the degradation of MTBE was observed along with the consumption of n-octane. Different K s values for MTBE were observed for cells grown with or without n-octane, suggesting that different enzymes are responsible for the oxidation of MTBE in cells grown on n-octane or MTBE. The results are discussed in terms of their impacts on our understanding of MTBE biodegradation and cometabolism.

Individual or synchronous biodegradation of di-n-butyl phthalate and phenol by Rhodococcus ruber strain DP-2

The bacterial strain DP-2, identified as Rhodococcus ruber, is able to effectively degrade di-n-butyl phthalate (DBP) and phenol. Degradation kinetics of DBP and phenol at different initial concentrations revealed DBP and phenol degradation to fit modified first-order models. The half-life of DBP degradation ranged from 15.81 to 27.75h and phenol degradation from 14.52 to 45.52h under the initial concentrations of 600-1200mg/L. When strain DP-2 was cultured with a mixture of DBP (800mg/L) and phenol (700mg/L), DBP degradation rate was found to be only slightly influenced; however, phthalic acid (PA) accumulated, and phenol degradation was clearly inhibited during synchronous degradation. Transcriptional levels of degradation genes, phenol hydroxylase (pheu) and phthalate 3,4-dioxygenase (pht), decreased significantly more during synchronous degradation than during individual degradation. Quantitative estimation of individual or synchronous degradation kinetics is essential to manage mixed hazardous compounds through biodegradation in industrial waste disposal.

Degradation potential and microbial community structure of heavy oil-enriched microbial consortia from mangrove sediments in Okinawa, Japan

Mangroves constitute valuable coastal resources that are vulnerable to oil pollution. One of the major processes to remove oil from contaminated mangrove sediment is microbial degradation. A study on heavy oil- and hydrocarbon-degrading bacterial consortia from mangrove sediments in Okinawa, Japan was performed to evaluate their capacity to biodegrade and their microbial community composition. Surface sediment samples were obtained from mangrove sites in Okinawa (Teima, Oura, and Okukubi) and enriched with heavy oil as the sole carbon and energy source. The results revealed that all enriched microbial consortia degraded more than 20% of heavy oil in 21 days. The K1 consortium from Okukubi site showed the most extensive degradative capacity after 7 and 21 days. All consortia degraded more than 50% of hexadecane but had little ability to degrade polycyclic aromatic hydrocarbons (PAHs). The consortia were dominated by Pseudomonas or Burkholderia. When incubated in the presence of hydrocarbon compounds, the active bacterial community shifted to favor the dominance of Pseudomonas. The K1 consortium was a superior degrader, demonstrating the highest ability to degrade aliphatic and aromatic hydrocarbon compounds; it was even able to degrade heavy oil at a concentration of 15%(w/v). The dominance and turn-over of Pseudomonas and Burkholderia in the consortia suggest an important ecological role for and relationship between these two genera in the mangrove sediments of Okinawa.