Influence of phenol on the biodegradation of pyridine by freely suspended and immobilized Pseudomonas putida MK1

Liquefaction of lignocellulosic biomass for methane production: A review

Hydrothermal pretreatment (HTP) (Hot water extraction (HWE) and steam pretreatment) and pyrolysis have the potential to liquefy lignocellulosic biomass. HTP produces hydrolysate, consisting mainly of solubilized hemicellulose, while pyrolysis produces aqueous pyrolysis liquid (APL). The liquid products, either as main products or by-product, can be used as anaerobic digestion (AD) feeds, overcoming shortcomings of solid-state AD (SS-AD). This paper reviews HWE, steam pretreatment, and pyrolysis pretreatment methods used to liquefy lignocellulosic biomass, AD of liquefied products, effects of inhibition from intermediate by-products such as furan and phenolic compounds, and pretreatment tuning to increase methane yield. HTP, focusing on methane production, produces less inhibitory compounds when carried out at moderate temperatures. APL is a challenging feed for AD due to its complexity, including various inhibitory substances. Pre-treatment of biomass before pyrolysis, adaptation of microorganism to inhibitors, and additives, such as biochar, may help the AD cultures cope with inhibitors in APL.

UV activation of the pi bond in pyridine for efficient pyridine degradation and mineralization by UV/H2O2 treatment

Pyridine and organics containing pyridine rings are widely used but persist in the environment and cause toxic pollution. Due to the attraction of the nitrogen atoms to the electrons in the pi bond, the pyridine ring is difficult to oxidize by oxidant. Here, we propose that ultraviolet (UV) irradiation activates the electrons in the pi bond and enables combination with the hydroxyl radical (OH) originating from hydrogen peroxide (H₂O₂) to eliminate pyridine quickly and mineralize the byproducts. The removal rates of pyridine and total organic carbon (TOC) were compared in different treatments: UV irradiation, UV/H₂O₂ treatment and Fenton oxidation with different initial pyridine concentrations, pH values and H₂O₂ concentrations. The UV/H₂O₂ treatment yielded a higher pyridine removal rate and greater mineralization than the other treatments. The removal rate of pyridine was highest in neutral aqueous solution and H₂O₂ concentration of 10 mM. At an initial H₂O₂ concentration of 10 mM, more than 90% of the pyridine was degraded in 10 min, and approximately 70% of the TOC was removed in 60 min. The absorption of UV light at 254 nm by the pi bond of pyridine can accelerate the damage to the stable pyridine structure, especially in the presence of OH. This study provides a promising alternative for the removal and mineralization of pyridine ring-containing materials.

Improved Removal of Quinoline from Wastewater Using Coke Powder with Inorganic Ions

In this paper, laboratory batch adsorption tests were performed to study the adsorption behavior of coke powder in a quinoline aqueous solution with the absence and presence of inorganic ions (K+ and Ca2+). Adsorption isotherms, thermodynamic parameters, and kinetic models were used to understand the sorption mechanism, and zeta potential measurements were performed to elucidate the effect of the inorganic ions on the adsorption. The results showed that coke powder exhibited a reasonably good adsorption performance due to its pore structure and surface characteristics, and the presence of K+ and Ca2+ could further improve the adsorption. Without inorganic ions, the adsorption capacity of coke powder for quinoline and the removal efficiency of quinoline were 1.27 mg/g and 84.90%, respectively. At the ion concentration of 15 mmol, the adsorption capacity of coke powder and quinoline removal efficiency in the presence of K+ reached 1.38 mg/g and 92.02%, respectively, whereas those in the solutions with Ca2+ reached 1.40 mg/g and 93.31%, respectively. It was found that the adsorption of quinoline onto coke powder in the absence and presence of inorganic ions fit the Freundlich isotherm. Changes in the Gibbs free energy, the heat of adsorption, the entropy, and the activation energy of adsorption suggest that the adsorption was spontaneous and exothermic, which was dominated by physical adsorption, and that the added K+ and Ca2+ would favor the adsorption. In addition, the pseudo-second-order kinetic model was found to provide the best fit to the adsorption kinetic data, and K+ and Ca2+ increased the rate of quinoline adsorbed onto coke power. This improved adsorption due to inorganic ions was found to be a consequence of the decrease in the surface potential of coke powder particles, which resulted in a reduced thickness of water film around particles, as well as a decreased electrostatic repulsion between coke powder particles and quinoline molecules.

Adsorptive Removal of Pyridine in Simulation Wastewater Using Coke Powder

Pyridine is a toxic component in industrial wastewater, which is difficult to remove using conventional methods. In this study, the cost-effective coke powder was used to remove pyridine from a pyridine simulation wastewater. The removal efficiency and adsorption capacity of pyridine reached up to 67.32% and 0.4488 mg/g, respectively, at a coke powder concentration of 60 mg/L and an adsorption time of 30 min. The pyridine removal efficiency and adsorption capacity of coke powder reached saturation when the initial concentration was 40 mg/L. The pH of 2–12 in the solution was found to have little effect on the pyridine adsorption process of coke powder, while the coke powder with lower ash content was of better adsorbability for pyridine. The coke powder was regenerated by heat treatment, and reused for pyridine adsorption. It was found that the pyridine removal efficiency slightly decreased after nine times of reuse, in addition to a small cumulative weight loss rate of coke powder. Adsorption isotherm analysis showed that the adsorption of pyridine by coke powder could be well described by the Freundlich isothermal adsorption model, indicating multi-molecular layers mainly dominated the adsorption of pyridine on the surface of coke powder.

Inhibitors degradation and microbial response during continuous anaerobic conversion of hydrothermal liquefaction wastewater

One critical challenge of hydrothermal liquefaction (HTL) is its complex aqueous product, which has a high concentration of organic pollutants (up to 100gCOD/L) and diverse fermentation inhibitors, such as furfural, phenolics and N-heterocyclic compounds. Here we report continuous anaerobic digestion of HTL wastewater via an up-flow anaerobic sludge bed reactor (UASB) and packed bed reactor (PBR). Specifically, we investigated the transformation of fermentation inhibitors and microbial response. GC-MS identified the complete degradation of furfural and 5-hydroxymethylfurfural (5-HMF), and partial degradation (54.0-74.6%) of organic nitrogen and phenolic compounds, including 3-hydroxypyridine, phenol and 4-ethyl-phenol. Illumina MiSeq sequencing revealed that the bacteria families related to detoxification increased in response to the HTL aqueous phase. In addition, the increase of acetate-oxidizing bacteria in UASB and acetogens in PBR showed a strengthened acetogenesis. As for the archaeal communities, an increase in hydrogenotrophic methanogens was observed. Based on GC-MS/HPLC and microbial analysis, we speculate that dominant fermentation inhibitors were transformed into intermediates (Acetyl-CoA and acetate), further contributing to biomethane formation.

Immobilization of Microbes for Bioremediation of Crude Oil Polluted Environments: A Mini Review

Petroleum hydrocarbons are the most common environmental pollutants in the world and oil spills pose a great hazard to terrestrial and marine ecosystems. Oil pollution may arise either accidentally or operationally whenever oil is produced, transported, stored and processed or used at sea or on land. Oil spills are a major menace to the environment as they severely damage the surrounding ecosystems. To improve the survival and retention of the bioremediation agents in the contaminated sites, bacterial cells must be immobilized. Immobilized cells are widely tested for a variety of applications. There are many types of support and immobilization techniques that can be selected based on the sort of application. In this review article, we have discussed the potential of immobilized microbial cells to degrade petroleum hydrocarbons. In some studies, enhanced degradation with immobilized cells as compared to free living bacterial cells for the treatment of oil contaminated areas have been shown. It was demonstrated that immobilized cell to be effective and is better, faster, and can be occurred for a longer period.

Bioaugmentation with a pyridine-degrading bacterium in a membrane bioreactor treating pharmaceutical wastewater

The bacterial strain Paracoccus denitrificans W12, which could utilize pyridine as its sole source of carbon and nitrogen, was added into a membrane bioreactor (MBR) to enhance the treatment of a pharmaceutical wastewater. The treatment efficiencies investigated showed that the removal of chemical oxygen demand, total nitrogen, and total phosphorus were similar between bioaugmented and non-bioaugmented MBRs, however, significant removal of pyridine was obtained in the bioaugmented reactor. When the hydraulic retention time was 60 hr and the influent concentration of pyridine was 250-500 mg/L, the mean effluent concentration of pyridine without adding W12 was 57.2 mg/L, while the pyridine was degraded to an average of 10.2 mg/L with addition of W12. The bacterial community structure of activated sludge during the bioaugmented treatment was analyzed using polymerase chain reaction -denaturing gradient gel electrophoresis (PCR-DGGE). The results showed that the W12 inoculum reversed the decline of microbial community diversity, however, the similarity between bacterial community structure of the original sludge and that of the sludge after bioaugmentation decreased steadily during the wastewater treatment. Sequencing of the DNA recovered from DGGE gel indicated that Flavobacteriaceae sp., Sphingobium sp., Comamonas sp., and Hyphomicrobium sp. were the dominant organisms in time sequence in the bacterial community in the bioaugmented MBR. This implied that the bioaugmentation was affected by the adjustment of whole bacterial community structure in the inhospitable environment, rather than being due solely to the degradation performance of the bacterium added.

Persistent organic pollutants induced protein expression and immunocrossreactivity by Stenotrophomonas maltophilia PM102: a prospective bioremediating candidate

A novel bacterium capable of growth on trichloroethylene as the sole carbon source was identified as Stenotrophomonas maltophilia PM102 by 16S rDNA sequencing (accession number of NCBI GenBank: JQ797560). In this paper, we report the growth pattern, TCE degradation, and total proteome of this bacterium in presence of various other carbon sources: toluene, phenol, glucose, chloroform, and benzene. TCE degradation was comparatively enhanced in presence of benzene. Densitometric analysis of the intracellular protein profile revealed four proteins of 78.6, 35.14, 26.2, and 20.47 kDa while the extracellular protein profile revealed two distinct bands at 14 kDa and 11 kDa that were induced by TCE, benzene, toluene, and chloroform but absent in the glucose lane. A rabbit was immunised with the total protein extracted from the bacteria grown in 0.2% TCE + 0.2% peptone. Antibody preadsorbed on proteins from peptone grown PM102 cells reacted with a single protein of 35.14 kDa (analysed by MALDI-TOF-mass-spectrometry) from TCE, benzene, toluene, or chloroform grown cells. No reaction was seen for proteins of PM102 grown with glucose. The PM102 strain was immobilised in calcium alginate beads, and TCE degradation by immobilised cells was almost double of that by free cells. The beads could be reused 8 times.

Bacterial pyridine hydroxylation is ubiquitous in environment

Ten phenol-degrading bacterial strains were isolated from three geographically distant environments. Five of them, identified as Diaphorobacter, Acidovorax, Acinetobacter (two strains), and Corynebacterium, could additionally transform pyridine, through the transcription of phenol hydroxylase genes induced both by phenol and pyridine. HPLC-UV and LC-MS analyses indicated that one metabolite (m/e = 96.07) with the same molecular weight as monohydroxylated pyridine was produced from the five phenol-degrading strains, when pyridine was the sole carbon source. Phenol (50 mg l(-1)) could initially inhibit and later stimulate the pyridine transformation. In addition, heterologous expression of the phenol hydroxylase gene (pheKLMNOP) resulted in the detection of monohydroxylated pyridine, which confirmed the phenol hydroxylase could catalyze pyridine hydroxylation. Phylogeny of the phenol hydroxylase genes revealed that the genes from the five pyridine-hydroxylating strains form a clade with each other and with those catalyzing the hydroxylation of phenol, BTEX (acronym of benzene, toluene, ethylbenzene, and xylene), and trichloroethylene. These results suggest that pyridine transformation via hydroxylation by phenol hydroxylase may be prevalent in environments than expected.

Degradation of pyridine by one Rhodococcus strain in the presence of chromium (VI) or phenol

A Rhodococcus strain, Chr-9, which has the ability to degrade pyridine and phenol and reduce chromium (VI) (Cr (VI)) was isolated. The strain could grow with pyridine as the sole carbon and nitrogen source, and its pyridine-degradation capability was enhanced by 100 mg l(-1) phenol; however, the degradation of pyridine was inhibited when the phenol concentration was greater than 400 mg l(-1). The hydroxylation of pyridine suggested that the stimulation and inhibition of phenol to the pyridine degradation may be attributed to competition of phenol and pyridine for the hydroxylase gene. Strain Chr-9 was also able to reduce Cr (VI) when glucose and LB was used as the carbon source; however, the Cr (VI) reduction did not occur when pyridine was the sole carbon and energy source. In addition, strain Chr-9 could reduce Cr (VI) and simultaneously degrade pyridine in the presence of glucose. To the best of our knowledge, strain Chr-9 is the first Rhodococcus strain reported to degrade pyridine in the presence of Cr (VI), and the first strain with the pyridine degradation being stimulated by low concentrations of phenol.

Dual substrates biodegradation kinetics of m-cresol and pyridine by Lysinibacillus cresolivorans

Phenols and N-heterocyclic compounds are found to co-exist in actual wastewater, especially in petrochemical and coking wastewater. Lysinibacillus cresolivorans, a bacterium capable of phenol-biodegradation was used to study the substrate interactions of m-cresol and pyridine as single and dual substrates. The cell growth and substrate biodegradation kinetics were also investigated with initial m-cresol concentrations varying from 0 to 1200 mg/L and pyridine concentrations varying from 0 to 150 mg/L. The single substrate kinetics was well described by the Haldane kinetic models. The single-substrate parameter values of m-cresol on cell growth were μ(max)=0.89 h(-1), K(s)=426.25 mg/L, K(i)=51.26 mg/L and μ(max)=0.0925 h(-1), K(s)=60.28 mg/L, K(i)=16.17 mg/L for cell growth on pyridine. Inhibitory effects of substrates were observed when cells were grown on the mixed substrates. The interaction parameter I(m,p) (0.76) was greater than I(m,p) (0.11), which indicated that m-cresol inhibited the utilization of pyridine much more than pyridine inhibited the biodegradation of m-cresol. The study showed a good potential of L. cresolivorans in degrading mixed substrates of m-cresol and pyridine.

Bioremediation of crude oil-contaminated soil: comparison of different biostimulation and bioaugmentation treatments

Biostimulation with inorganic fertilizer and bioaugmentation with hydrocarbon utilizing indigenous bacteria were employed as remedial options for 12 weeks in a crude oil-contaminated soil. To promote oil removal, biocarrier for immobilization of indigenous hydrocarbon-degrading bacteria was developed using peanut hull powder. Biodegradation was enhanced with free-living bacterial culture and biocarrier with a total petroleum hydrocarbon removal ranging from 26% to 61% after a 12-week treatment. Oil removal was also enhanced when peanut hull powder was only used as a bulking agent, which accelerated the mass transfer rate of water, oxygen, nutrients and hydrocarbons, and provided nutrition for the microflora. Dehydrogenase activity in soil was remarkably enhanced by the application of carrier material. Metabolites of polycyclic aromatic hydrocarbons were identified by Fourier transform ion cyclotron resonance mass spectrometry.

Microbial degradation and metabolic pathway of pyridine by a Paracoccus sp. strain BW001

A bacterial strain using pyridine as sole carbon, nitrogen and energy source was isolated from the activated sludge of a coking wastewater treatment plant. By means of morphologic observation, physiological characteristics study and 16S rRNA gene sequence analysis, the strain was identified as the species of Paracoccus. The strain could degrade 2,614 mg l(-1) of pyridine completely within 49.5 h. Experiment designed to track the metabolic pathway showed that pyridine ring was cleaved between the C2 and N, then the mineralization of the carbonous intermediate products may comply with the early proposed pathway and the transformation of the nitrogen may proceed on a new pathway of simultaneous heterotrophic nitrification and aerobic denitrification. During the degradation, NH3-N occurred and increased along with the decrease of pyridine in the solution; but the total nitrogen decreased steadily and equaled to the quantity of NH3-N when pyridine was degraded completely. Adding glucose into the medium as the extra carbon source would expedite the biodegradation of pyridine and the transformation of the nitrogen. The fragments of nirS gene and nosZ gene were amplified which implied that the BW001 had the potential abilities to reduce NO2- to NO and/or N2O, and then to N2.