Styrene Degradation Research Articles

Biotrickling filtration of airborne styrene: A comparison of filtration media

ABSTRACTThis study compares the performances of fern and plastic chips as packing media for the biofiltration of a styrene-laden waste gas stream emitted in a plant for the manufacture of plastic door plates. Fern chips (with a specific surface area of 1090 m2 m−3) and plastic chips (with a specific surface area of 610 m2 m−3) were packed into a pilot-scale biotrickling filter with a total medium volume of 50 L for the performance test. Field waste gas with styrene concentrations in the range of 161–2390 mg Am−3 at 28–30 °C) was introduced to the bed and a fixed empty-bed retention time (EBRT) of 21 sec, a volumetric gas flow rate of 8.57 m3 hr−1, and superficial gas velocity of 53.6 m hr−1 were maintained throughout the experimental period. Nutrients containing metal salts, nitrogen, phosphorus, and milk were supplemented to the filters for maintaining the microbial activities. Results reveal that the biotrickling filter developed in this study had the highest styrene monomer (SM) elimination capacities (170 g m−3 hr−1 for fern-chip packing and 300 g m−3 hr−1 for plastic-chip packing) among those cited in the literature. The plastic medium is a favorable substitute for endangered fern chips. The thermal-setting nature of plastic chips limits their recycle and reuse as raw materials, and the study provides an opportunity for the utilization of the materials.Implications: Biotreatment of contaminants in air streams offers an inexpensive and efficient alternative to conventional technologies. Biofiltration has a great potential for the degradation of gas-borne styrene and total hydrocarbon (THC) removal efficiency of around 80%. The objective of this research was to compare the performances of fern chips and a kind of plastic chips as packing media for biofiltration of the styrene-laden waste gas stream emitted from cutting operations of stripes of premixed unsaturated polyester (UP) and styrene paste before hot-pressing operations for making plastic door plates. From a practical point of view, the plastic medium can be a good substitute medium for fern chips, which has been declared as a protected plant. This study provides an experimentally verified model for the design and operation of such biotreatment systems.

Enhanced visible-light photocatalytic activity to volatile organic compounds degradation and deactivation resistance mechanism of titania confined inside a metal-organic framework

Poor visible-light-driven activity and deactivation property as well as wide band gap of the most common TiO2 photocatalyst significantly limits its practical application in volatile organic compounds (VOCs) purification. In this study, tiny TiO2 nanoparticles incorporated into a typical metal-organic framework (MOF), NH2-UiO-66, with controllable TiO2 content and size, were synthesized based on the hard-soft acid-base (HSAB) principle and applied to VOCs purification. Compared to bare TiO2, the TiO2@NH2-UiO-66 composites could extend the optical absorption to the visible light range and accelerate the photogenerated electrons-holes separation, due to the excellent interface contact between TiO2 and NH2-UiO-66. Moreover, the abundant interconnected 3D cavities of the outer MOF allowed for VOCs to easily diffuse into the pores, producing a concentration microenvironment around the encapsulated TiO2. The TiO2@NH2-UiO-66 composites exhibited a markedly improved photocatalytic efficiency and a good resistance to deactivation during the photocatalytic degradation of gaseous styrene under visible light illumination, which were associated with the synergetic effects between the TiO2 and MOF. The TiO2@NH2-UiO-66 with 5 wt% TiO2 could efficiently mineralize styrene to CO2 to some extent companying with the removal ratio >99% within 600 min, whereas the removal efficiency over the bare TiO2 only 32.5%.

A Review: The Styrene Metabolizing Cascade of Side-Chain Oxygenation as Biotechnological Basis to Gain Various Valuable Compounds.

Styrene is one of the most produced and processed chemicals worldwide and is released into the environment during widespread processing. But, it is also produced from plants and microorganisms. The natural occurrence of styrene led to several microbiological strategies to form and also to degrade styrene. One pathway designated as side-chain oxygenation has been reported as a specific route for the styrene degradation among microorganisms. It comprises the following enzymes: styrene monooxygenase (SMO; NADH-consuming and FAD-dependent, two-component system), styrene oxide isomerase (SOI; cofactor independent, membrane-bound protein) and phenylacetaldehyde dehydrogenase (PAD; NAD+-consuming) and allows an intrinsic cofactor regeneration. This specific way harbors a high potential for biotechnological use. Based on the enzymatic steps involved in this degradation route, important reactions can be realized from a large number of substrates which gain access to different interesting precursors for further applications. Furthermore, stereochemical transformations are possible, offering chiral products at high enantiomeric excess. This review provides an actual view on the microbiological styrene degradation followed by a detailed discussion on the enzymes of the side-chain oxygenation. Furthermore, the potential of the single enzyme reactions as well as the respective multi-step syntheses using the complete enzyme cascade are discussed in order to gain styrene oxides, phenylacetaldehydes, or phenylacetic acids (e.g., ibuprofen). Altered routes combining these putative biocatalysts with other enzymes are additionally described. Thus, the substrates spectrum can be enhanced and additional products as phenylethanols or phenylethylamines are reachable. Finally, additional enzymes with similar activities toward styrene and its metabolic intermediates are shown in order to modify the cascade described above or to use these enzyme independently for biotechnological application.

Draft Genome Sequence of Pseudomonas putida CA-3, a Bacterium Capable of Styrene Degradation and Medium-Chain-Length Polyhydroxyalkanoate Synthesis.

ABSTRACTPseudomonas putida strain CA-3 is an industrial bioreactor isolate capable of synthesizing biodegradable polyhydroxyalkanoate polymers via the metabolism of styrene and other unrelated carbon sources. The pathways involved are subject to regulation by global cellular processes. The draft genome sequence is 6,177,154 bp long and contains 5,608 predicted coding sequences.

Biosynthesis of polyhydroxyalkanoates from styrene by Enterobacter spp. isolated from polluted environment

Styrene and its metabolites are known to have serious adverse effects on human health and hence, strategies to prevent its release, eradicate it from the environment, and understand its route of degradation are being considered. A total of 18 strains were isolated from 4 samples of diesel contaminated soils. Among them 5 strains were selected for their ability to degrade styrene and use it as a sole carbon source to produce PHA. These strains were identified as Enterobacter spp. on the basis of 16S rRNA gene sequencing. Bacteria were screened for their ability to produce PHA by utilizing glucose and styrene as a carbon sources. Screening for PHA production was done by Nile blue A, Sudan black B, and phase contrast microscopy and the selected 3 strains showed positive results. Growth kinetics along with time profiling of PHA was performed for glucose and styrene as carbon sources. PHA extraction was done at equal intervals of 12 h by sodium hypochlorite method which showed that these strains accumulate maximum amount of PHA after 48 h in glucose (30.60%). FTIR analysis of PHA was done which revealed homopolymer PHB and copolymer (PHB-co-PHV) production in strains by utilizing glucose and styrene. Gas chromatography mass spectrometry was carried out to identify the metabolites produced by bacterial strains grown on styrene. Metabolites of styrene degradation included propyne and phenylalanine. Genomic DNA isolation was carried out to amplify phaC gene which encodes PHA synthase enzyme. The conversion of styrene to polyhydroxyalkanoates (PHA) provides a new and unique link between an aromatic environmental pollutant and aliphatic PHA accumulation.

Fabrication of Au/TiO2 nanowires@carbon fiber paper ternary composite for visible-light photocatalytic degradation of gaseous styrene

In this work, Au nanoparticles decorated TiO2 nanowires onto hierarchically porous carbon fiber paper (Au/TiO2NWs@CFP) ternary composite was synthesized using a combining approach of wet coating, hydrothermal growth and photoreduction. Characterization revealed that the 3D network of CFP was homogeneously encapsulated by Au nanoparticles (1.8nm in diameter) decorated anatase TiO2 NWs with diameter of 15–30nm and length of several microns. The formation of the Au/TiO2NWs@CFP composite undergoes the following three key-steps: formation of TiO2 islands on CFP, in-situ growth of TiO2 NWs on the TiO2 islands and deposition of Au NPs onto TiO2 NWs. Photocatalytic degradation of gaseous styrene showed that Au/TiO2NWs@CFP exhibited the excellent photoactivity and photostability under visible light irradiation. It is attributed to the synergistic effect of the three components (TiO2 NWs, CFP and Au nanoparticles), which can enhance visible light absorption intensity, reduce the recombination of photogenerated charges and holes, as well as improve the adsorption of organic pollutants. The present strategy would offer an effective way for the synthesis of ternary composite photocatalyst and its application to air purification under visible light irradiation.

Exploring the Degradation of Acrylonitrile Butadiene Styrene Resin Certified Reference Material for Heavy Metal Analysis

The degradation of acrylonitrile butadiene styrene (ABS) resin certified reference materials (CRMs) for heavy metal analysis was found. The masses of the ABS resin CRMs increased after the certification time, which resulted in decreasing the concentrations of elements. Other ABS resin CRMs contained 1 order of magnitude lower concentrations of same elements and showed no change for their concentrations and masses. The carbon and oxygen in degraded ABS resin CRM were ca. 4% lower and ca. 4% higher, respectively, than those of the nondegraded one. The increases for both ether (C–O–C) and ketone (C═O) groups and the decrease of C═C double bond were also observed for degraded ABS resin CRMs. From these results, it was considered that the oxidation occurred for the degraded ABS resin CRMs during the storage period. The Cr(III)-acetylacetonate in the degraded ABS resin CRMs was considered to be a metal catalyst to promote the oxidation.

Effect of loading types on performance characteristics of a trickle-bed bioreactor and biofilter during styrene/acetone vapor biofiltration

ABSTRACTA 2:1 (w/w) mixture of styrene (STY) and acetone (AC) was subjected to lab-scale biofiltration under varied loading in both a trickle bed reactor (TBR) and biofilter (BF) to investigate substrate interactions and determine the limits of biofiltration efficiency of typical binary air pollutant mixtures containing both hydrophobic and polar components. A comparison of the STY/AC mixture degradation in the TBR and BF revealed higher pollutant removal efficiencies and degradation rates in the TBR, with the pollutant concentrations increasing up to the overloading limit. The maximum styrene degradation rates were 12 and 8 gc m−3 h−1 for the TBR and BF, respectively. However, the order of performance switched in favor of the BF when the loading was conducted by increasing air flow rate while keeping the inlet styrene concentration (Cin) constant in contrast to loading by increasing Cin. This switch may be due to a drastic difference in the effective surface area between these two reactors, so the biofilter becomes the reactor of choice when the rate-limiting step switches from biochemical processes to mass transfer by changing the loading mode. The presence of acetone in the mixture decreased the efficiency of styrene degradation and its degradation rate at high loadings. When the overloading was lifted by lowering the pollutant inlet concentrations, short-term back-stripping of both substrates in both reactors into the outlet air was observed, with a subsequent gradual recovery taking several hours and days in the BF and TBR, respectively. Removal of excess biomass from the TBR significantly improved the reactor performance. Identification of the cultivable strains, which was performed on Day 763 of continuous operation, showed the presence of 7 G− bacteria, 2 G+ bacteria and 4 fungi. Flies and larvae of Lycoriella nigripes survived half a year of the biofilter operation by feeding on the biofilm resulting in the maintenance of a nearly constant pressure drop.

Isolation and genome sequencing of four Arctic marine Psychrobacter strains exhibiting multicopper oxidase activity.

BackgroundMarine cold-temperature environments are an invaluable source of psychrophilic microbial life for new biodiscoveries. An Arctic marine bacterial strain collection was established consisting of 1448 individual isolates originating from biota, water and sediment samples taken at a various depth in the Barents Sea, North of mainland Norway, with an all year round seawater temperature of 4 °C. The entire collection was subjected to high-throughput screening for detection of extracellular laccase activity with guaiacol as a substrate.ResultsIn total, 13 laccase-positive isolates were identified, all belonging to the Psychrobacter genus. From the most diverse four strains, based on 16S rRNA gene sequence analysis, all originating from the same Botryllus sp. colonial ascidian tunicate sample, genomic DNA was isolated and genome sequenced using a combined approach of whole genome shotgun and 8 kb mate-pair library sequencing on an Illumina MiSeq platform. The genomes were assembled and revealed genome sizes between 3.29 and 3.52 Mbp with an average G + C content of around 42 %, with one to seven plasmids present in the four strains. Bioinformatics based genome mining was performed to describe the metabolic potential of these four strains and to identify gene candidates potentially responsible for the observed laccase-positive phenotype. Up to two different laccase-like multicopper oxidase (LMCO) encoding gene candidates were identified in each of the four strains. Heterologous expression of P11F6-LMCO and P11G5-LMCO2 in Escherichia coli BL21 (DE3) resulted in recombinant proteins exhibiting 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and guaiacol oxidizing activity.ConclusionsThirteen Psychrobacter species with laccase-positive phenotype were isolated from a collection of Arctic marine bacteria. Four of the isolates were genome sequenced. The overall genome features were similar to other publicly available Psychrobacter genome sequences except for P11G5 harboring seven plasmids. However, there were differences at the pathway level as genes associated with degradation of phenolic compounds, nicotine, phenylalanine, styrene, ethylbenzene, and ethanolamine were detected only in the Psychrobacter strains reported in this study while they were absent among the other publicly available Psychrobacter genomes. In addition, six gene candidates were identified by genome mining and shown to possess T1, T2 and T3 copper binding sites as the main signature of the three-domain laccases. P11F6-LMCO and P11G5-LMCO2 were recombinantly expressed and shown to be active when ABTS and guaiacol were used as substrates.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2445-4) contains supplementary material, which is available to authorized users.

Application of response surface methodology for optimization of operational variables in photodegradation of aqueous styrene under visible light

In this study, the center composite design in response surface methodology was firstly applied to optimize the photocatalytic degradation of aqueous styrene under visible light. Twenty experiments were done by adjusting three parameters (initial concentration of styrene, concentration of catalyst and initial pH of reaction mixture) at five levels by the method of multiple variable analyses. Based on the experimental design, an empirical expression was firstly established and subsequently applied to predict the photocatalytic degradation efficiency of aqueous styrene under visible light. The results showed that the experimental photocatalytic degradation efficiencies are in accordance with the theoretically predicted values very well with a high correlation. The strongest interaction between the parameters assessed was concentration of catalyst /initial pH of mixture. Optimal experimental conditions for arbitrary aqueous styrene concentration of 115 mg L−1 were found initial pH 6.8 and catalyst loading 2 g L−1. The photocatalytic degradation efficiency of aqueous styrene under this condition reached to about 84%. Furthermore, the main degradation intermediate produced in this process was identified by GC/MS technique. The photocatalytic mineralization of styrene in aqueous solution has been studied by TOC.

Production of a recombinant membrane protein in an Escherichia coli strain for the whole cell biosynthesis of phenylacetic acids

The styrene oxide isomerase (SOI) represents a membrane-bound enzyme of the microbial styrene degradation pathway and has been discussed as promising biocatalyst. It catalyzes the isomerization of styrene oxide to phenylacetaldehyde. In this study a styC gene, which encodes the SOI of Rhodococcus opacus 1CP, was optimized for optimal expression in Escherichia coli BL21(DE3) pLysS. The expression of this synthetic styC was investigated and subsequently optimized. Highly active biomass was obtained yielding an SOI activity of 44.5±8.7Umg−1 after 10h. This represents the highest SOI activity reported for crude cell extracts of SOI-containing bacterial strains. Remarkably, this biomass can be applied as whole cell biocatalyst for the production of phenylacetic acids from styrene oxides. In the case of non-substituted styrene oxide, nearly 730mgl−1 phenylacetic acid (∼85% yield) was formed over a period of 20 days.

Photocatalytic Degradation of Styrene in Aqueous Solution: Central Composite Design Optimization

In this study, the response surface methodology was first applied to optimize the photocatalytic degradation of styrene in aqueous phase under UV/TiO2 system. Twenty experiments were done by adjusting three parameters (styrene concentration, TiO2 dose, and pH) at five levels. Optimal experimental conditions for arbitrary aqueous styrene concentration (115 mg L−1) were found: initial pH 7 and TiO2 loading 2 g L−1 with photocatalytic degradation efficiency of 79.2%. Furthermore, the main degradation intermediate produced was identified by GC/MS. The total organic carbon results revealed that the photocatalysis process could be effectively mineralized. Kinetics of the photocatalytic reaction followed a pseudo-first-order model.

Styrene is sensed by the N-terminal PAS sensor domain of StyS, a double sensor kinase from the styrene-degrading bacterium Pseudomonas fluorescens ST

In Pseudomonas fluorescens ST, the expression of the pathway for the degradation of the toxic compound styrene is induced by the substrate (i.e., styrene) and repressed by alternative carbon sources. This regulation relies on a two-component system consisting of the sensor kinase StyS and the response regulator StyR. StyS belongs to the group of hybrid “double sensor kinases”, a unique family of sensor kinases having two ATP catalytic domains, each one preceded by a PAS domain. Here, the styrene-based phosphorylation of StyS is reported. Styrene is specifically sensed by the StyS N-terminal PAS sensor domain, enhancing the StyS phosphorylation level.

Synthesis of N-TiO2: Stability and Visible Light Activity for Aqueous Styrene Degradation

Nitrogen-doped TiO2 (N-TiO2) were prepared by the impregnation method using urea as a nitrogen source and TiO2-P25 as precursor. N-TiO2 was characterized by x-ray diffraction (XRD), UV–vis diffusion reflectance spectra (UV–vis DRS), Fourier transform infrared spectroscopy (FTIR), and x-ray photoelectron spectroscopy (XPS) techniques. XPS analysis indicates the incorporation of nitrogen in TiO2 lattice as O–Ti–N linkage. DRS spectra reveal the extended absorption to the visible range. Photocatalytic performance of the N-TiO2 was studied by testing the degradation rate of aqueous styrene under visible light. Also, the degradation kinetics of aqueous styrene and possibility of cyclic usage of N-TiO2 were investigated.

The complete genome of Burkholderia phenoliruptrix strain BR3459a, a symbiont of Mimosa flocculosa: highlighting the coexistence of symbiotic and pathogenic genes.

BackgroundBurkholderia species play an important ecological role related to xenobiosis, the promotion of plant growth, the biocontrol of agricultural diseases, and symbiotic and non-symbiotic biological nitrogen fixation. Here, we highlight our study as providing the first complete genome of a symbiotic strain of B. phenoliruptrix, BR3459a (=CLA1), which was originally isolated in Brazil from nodules of Mimosa flocculosa and is effective in fixing nitrogen in association with this leguminous species.ResultsGenomic comparisons with other pathogenic and non-pathogenic Burkholderia strains grouped B. phenoliruptrix BR3459a with plant-associated beneficial and environmental species, although it shares a high percentage of its gene repertoire with species of the B. cepacia complex (Bcc) and "pseudomallei" group. The genomic analyses showed that the bce genes involved in exopolysaccharide production are clustered together in the same genomic region, constituting part of the Group III cluster of non-pathogenic bacteria. Regarding environmental stresses, we highlight genes that might be relevant in responses to osmotic, heat, cold and general stresses. Furthermore, a number of particularly interesting genes involved in the machinery of the T1SS, T2SS, T3SS, T4ASS and T6SS secretion systems were identified. The xenobiotic properties of strain BR3459a were also investigated, and some enzymes involved in the degradation of styrene, nitrotoluene, dioxin, chlorocyclohexane, chlorobenzene and caprolactam were identified. The genomic analyses also revealed a large number of antibiotic-related genes, the most important of which were correlated with streptomycin and novobiocin. The symbiotic plasmid showed high sequence identity with the symbiotic plasmid of B. phymatum. Additionally, comparative analysis of 545 housekeeping genes among pathogenic and non-pathogenic Burkholderia species strongly supports the definition of a new genus for the second branch, which would include BR3459a.ConclusionsThe analyses of B. phenoliruptrix BR3459a showed key property of fixing nitrogen that together with genes for high tolerance to environmental stresses might explain a successful strategy of symbiosis in the tropics. The strain also harbours interesting sets of genes with biotechnological potential. However, the resemblance of certain genes to those of pathogenic Burkholderia raise concerns about large-scale applications in agriculture or for bioremediation.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-535) contains supplementary material, which is available to authorized users.

Ammonia and formaldehyde participate in the formation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in addition to creati(ni)ne and phenylacetaldehyde

The formation of formaldehyde from phenylacetaldehyde and phenylalanine, and the contribution of both formaldehyde and ammonia to the production of PhIP from phenylacetaldehyde and creatinine were studied in an attempt to clarify the reaction pathways that produce PhIP. Formaldehyde was produced by thermal degradation of phenylacetaldehyde and, to a lesser extent, also by degradation of phenylalanine, phenylethylamine, styrene, and creatinine. When formaldehyde was added to a mixture of phenylacetaldehyde and creatinine, PhIP yield was multiplied by nineteen. When formaldehyde and ammonia were simultaneously present, PhIP yield was multiplied by fifty and the Ea of the reaction decreased by 61%. All these results point to formaldehyde and ammonia as the two additional reactants required for PhIP formation from both phenylacetaldehyde/creati(ni)ne and phenylalanine/creati(ni)ne mixtures. A general pathway for PhIP formation is proposed. This pathway is suggested to be the main route for PhIP formation in foods.

The Effect of Relative Humidity On Chemical Degradation of Styrene Based Radiation Grafted Membranes in the PEFC

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The Effect of Relative Humidity on Chemical Degradation of Styrene Based Radiation Grafted Membranes in the PEFC

The chemical degradation of styrene based radiation grafted membranes has been investigated by testing the MEAs at 50% RH for 110 h and different current densities. Post-test analysis using FTIR spectroscopy was performed to qualitatively and quantitatively analyze membrane degradation. The results show that higher water content in the MEA leads to a higher degradation rate of styrene based radiation grafted membranes. A range of working hypotheses is discussed from the point of view of both formation rate of reactive intermediates and chain degradation mechanism of ionomers. The strong relative humidity dependency of membrane conductivity causes the poor performance in the fuel cell when the membrane is dry. Imbalanced humidification of reactant gases (e.g. 50% at cathode and 100% at anode) can decrease chemical degradation of styrene based radiation grafted membranes, meanwhile maintaining a fuel cell performance comparable to that under fully humidified conditions.

Thermal oxidative degradation of styrene-butadiene rubber (SBR) studied by 2D correlation analysis and kinetic analysis

The thermal oxidation degradation of styrene–butadiene rubber (SBR) was investigated by in situ FTIR, 2D-FTIR, and programming heating DSC. The results of analyses suggest that the degradation reaction is an autocatalytic process and mainly occurs on the aliphatic part instead of benzene pendants. Based on the results of in situ FTIR and 2D-FTIR, the oxidation process can be divided into three stages. In stage one, just two carbonyl peaks appear, namely 1,697 cm−1 (conjugate carbonyls) and 1,727 cm−1 (saturated carbonyls), and the generation speed is 1,697 > 1,727 cm−1. Yet the peaks appearing at 1,777 cm−1 belonged to peresters and anhydrides generating in stages two and three. The generation sequences are: 1,698 > 1,727 > 1,777 cm−1 for stage two; and 1,698 < 1,727 < 1,777 cm−1 for stage three. According to DSC results, the thermal oxidation of SBR contains four steps. The first step is the generation of alkyl radicals and the accumulation of hydroperoxide species. The second step is initial oxidation stage mainly producing conjugate carbonyls. The third step is deep oxidation process generating diverse carbonyls. The fourth is chain termination reaction, in which step the generation rates of anhydrides and peresters are the fastest due to bi-radical termination of alkoxy radicals and the consumption of conjugate carbonyl. Furthermore, crosslinking reactions occur during the whole thermal oxidation.

By‐passing the refinery for production of high‐value BTX derivatives

By‐passing the refinery for production of high‐value BTX derivatives