Adsorption and transformation of PAHs from water by a laccase-loading spider-type reactor

Anthracene detoxification by Laccases from indigenous fungal strains Trichoderma lixii FLU1 and Talaromyces pinophilus FLU12

The persistence and ubiquity of polycyclic aromatic hydrocarbons (PAHs) in the environment necessitate effective remediation strategies. Hence, this study investigated the potential of purified Laccases, TlFLU1L and TpFLU12L, from two indigenous fungi Trichoderma lixii FLU1 (TlFLU1) and Talaromyces pinophilus FLU12 (TpFLU12), respectively for the oxidation and detoxification of anthracene. Anthracene was degraded with vmax values of 3.51 ± 0.06 mg/L/h and 3.44 ± 0.06 mg/L/h, and Km values of 173.2 ± 0.06 mg/L and 73.3 ± 0.07 mg/L by TlFLU1L and TpFLU12L, respectively. The addition of a mediator compound 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) to the reaction system significantly increased the degradation of anthracene, with up to a 2.9-fold increase in vmax value and up to threefold decrease in Km values of TlFLU1L and TpFLU12L. The GC-MS analysis of the metabolites suggests that anthracene degradation follows one new pathway unique to the ABTS system-hydroxylation and carboxylation of C-1 and C-2 position of anthracene to form 3-hydroxy-2-naphthoic acid, before undergoing dioxygenation and side chain removal to form chromone which was later converted into benzoic acid and CO2. This pathway contrasts with the common dioxygenation route observed in the free Laccase system, which is observed in the second degradation pathways. Furthermore, toxicity tests using V. parahaemolyticus and HT-22 cells, respectively, demonstrated the non-toxic nature of Laccase-ABTS-mediated metabolites. Intriguingly, analysis of the expression level of Alzheimer's related genes in HT-22 cells exposed to degradation products revealed no induction of neurotoxicity unlike untreated cells. These findings propose a paradigm shift for bioremediation by highlighting the Laccase-ABTS system as a promising green technology due to its efficiency with the discovery of a potentially less harmful degradation pathway, and the production of non-toxic metabolites.

Unique Fiber Morphologies from Emulsion Electrospinning—A Case Study of Poly(ε-caprolactone) and Its Applications

The importance of electrospinning to produce biomimicking micro- and nano-fibrous matrices is realized by many who work in the area of fibers. Based on the solubility of the materials to be spun, organic solvents are typically utilized. The toxicity of the utilized organic solvent could be extremely important for various applications, including tissue engineering, biomedical, agricultural, etc. In addition, the high viscosities of such polymer solutions limit the use of high polymer concentrations and lower down productivity along with the limitations of obtaining desired fiber morphology. This emphasizes the need for a method that would allay worries about safety, toxicity, and environmental issues along with the limitations of using concentrated polymer solutions. To mitigate these issues, the use of emulsions as precursors for electrospinning has recently gained significant attention. Presence of dispersed and continuous phase in emulsion provides an easy route to incorporate sensitive bioactive functional moieties within the core-sheath fibers which otherwise could only be hardly achieved using cumbersome coaxial electrospinning process in solution or melt based approaches. This review presents a detailed understanding of emulsion behavior during electrospinning along with the role of various constituents and process parameters during fiber formation. Though many polymers have been studied for emulsion electrospinning, poly(ε-caprolactone) (PCL) is one of the most studied polymers for this technique. Therefore, electrospinning of PCL based emulsions is highlighted as unique case-study, to provide a detailed theoretical understanding, discussion of experimental results along with their suitable biomedical applications.

Simulation of novel jellyfish type of process for bioremediation application

A bioinspired device was fabricated as a sustainable remedial method and its performance as a membrane-enzyme reactor with cyclic ultrafiltration was investigated. The body of the jellyfish-like device was composed of two parts: 1) Jellyfish arms: Mono and co-axial electrospinning have been utilized to synthesize the flexible parts (e.g., multilayer membrane PS-PVDF/PAN/PS-PVDF) used for immobilization of aliphatic degrading enzymes, and 2) Jellyfish tentacles: Hollow fiber membranes were selected for physical immobilization of polycyclic aromatic hydrocarbon (PAH) degrading enzymes. To study the behavior of the membrane/enzyme reactor, the hollow fiber enzyme reactor with pulsation was operated by recycling an enzyme solution to assess ultrafiltration efficiency. A mathematical model was suggested to describe the experimental data obtained in this study to predict the effectiveness of the reactor for PAH removal. When testing the performance of the jellyfish-like device, those equipped with nanofibers with an oil sorption capacity of (10. ±0.7gdilbit/gfiber) were more effective at removing oil particles before they touched the hollow fiber membrane surface. Moreover, the reaction rate measured in a free soluble enzyme and a recirculating immobilized enzyme solution exhibited a slight difference in the kinetic parameter, K_m (0.03 and 0.021 mM) due to the internal diffusional resistance. Based on biodegradation studies, a synergistic effect between membrane adsorption, enzymatic degradation, and ultrafiltration was proposed for the removal of anthracene from the column of water.

A comprehensive insight into the application of white rot fungi and their lignocellulolytic enzymes in the removal of organic pollutants

Environmental problems resultant from organic pollutants are a major current challenge for modern societies. White rot fungi (WRF) are well known for their extensive organic compound degradation abilities. The unique oxidative and extracellular ligninolytic systems of WRF that exhibit low substrate specificity, enable them to display a considerable ability to transform or degrade different environmental contaminants. In recent decades, WRF and their ligninolytic enzymes have been widely applied in the removal of polycyclic aromatic hydrocarbons (PAHs), pharmaceutically active compounds (PhACs), endocrine disruptor compounds (EDCs), pesticides, synthetic dyes, and other environmental pollutants, wherein promising results have been achieved. This review focuses on advances in WRF-based bioremediation of organic pollutants over the last 10 years. We comprehensively document the application of WRF and their lignocellulolytic enzymes for removing organic pollutants. Moreover, potential problems and intriguing observations that are worthy of additional research attention are highlighted. Lastly, we discuss trends in WRF-remediation system development and avenues that should be considered to advance research in the field.

Enhancement and analysis of Anthracene degradation by Tween 80 in LMS-HOBt

This study examines the specific effect of Tween 80 on the conversion of anthracene (ANT) in laccase medium system regarding surfactant chemical changes and mechanism. The conversion rate and degradation products of ANT were investigated in different concentrations of Tween 80 solution. Between Tween 80 concentration 0-40 critical micelle concentrations (CMC), the kinetic parameter-k (h-1) and corresponding half-life T1/2 decreased with increasing concentration. When Tween 80 was above 20 CMC the laccase-medium system converted > 95% of ANT to anthraquinone within 12 h. During the entire enzymatic reaction, the laccase activity in the system increased with increasing Tween 80 concentration. Combined with GC/MS analysis of the product, it was speculated that hydrogens belonging to the ether-oxygen bond and carbon-carbon double bond α-CH of Tween 80, were removed by the laccase-media system, promoting its degradation. Additionally, enhanced activity caused by oxygen free radicals (ROS) such as RO• and ROO•, continuously oxidized Tween 80, which in turn produced free radicals while converting ANT. This study provides new theoretical support toward the application of surfactants in the elimination of polycyclic aromatic hydrocarbons.

Degradation of several polycyclic aromatic hydrocarbons by laccase in reverse micelle system

Remediation of polycyclic aromatic hydrocarbons (PAHs) in oily sludge has become the focus of attention. UV spectrophotometer analysis showed that four types of PAHs were found in sample, which including phenanthrene, anthracene, benzo(a)anthracene and benzo(b)fluoranthene. In order to degrade PAH effectively, the laccase reverse micelles system was proposed. The system protects laccase from being affected by organic phase. Reverse micelles were prepared by using isooctane to simulate oil. The optimum water content W₀ was 10 by measuring the electrical conductivity of the system. Under this condition, the effects of pH, temperature and ionic strength on the degradation rate of PAHs were investigated. Also, compared with that of non-immobilized laccase, the ratio between the secondary structures of laccase under different conditions was studied. The results showed that the highest laccase activity was obtained at pH 4.2 and 30 °C with 60 mmol/L KCl. Meanwhile, the structure of α-helix accounts for the largest proportion, and the ratio of α-helix in the laccase secondary structure in the laccase-reverse micelle system was higher than that of the non-immobilized one under this condition. Finally, predicting the reactive site of the degradation of polycyclic aromatic hydrocarbons was simulated by ORCA (Version 4.2.0). The application in oily sludge was further conducted. This study provides an effective method and basis for the degradation of PAHs in oily sludge.

Biodegradable bead-on-spring nanofibers releasing β-carotene for bone tissue engineering

Bead-on-string mats based on poly(lactide-co-glycolide) (PLGA) releasing β-carotene (βC) as a natural osteogen were fabricated and used for bone tissue engineering. Mesenchymal stem cells (MSCs) seeded on the scaffolds successfully differentiated to osteoblasts without using any a differential medium. The mats showed a small burst of β-carotene (24-27%) during the first day and a sustained slow release up to 21 days. The MTT and SEM results indicated good attachment and proliferation of MSCs on the scaffolds. Calcination of scaffolds and expression of RUNX2, SOX9, and osteonectin genes approved the differentiation of seeded MSCs to osteoblasts without using any external osteogenic differential agent. The scaffold loaded with 4% β-carotene not only induced the early phase of osteogenesis but also advanced the differentiation to the osteoblast maturation phase. Thus, these bead-on-string scaffolds can be used as a substrate for direct bone tissue engineering.

Sorptive removal of phenanthrene from aqueous solutions using magnetic and non-magnetic rice husk-derived biochars

A magnetically modified rice husk biochar (MBC) was successfully prepared by a hydrothermal method from original biochar (BC) and subsequently used to remove phenanthrene (PHE) from aqueous solutions. The porosity, specific surface area and hydrophobicity of BC were significantly improved (approx. two times) after magnetic modification. The adsorption data fitted well to pseudo-second-order kinetic and Langmuir models. Compared with BC, MBC had a faster adsorption rate and higher adsorption capacity of PHE. The adsorption equilibrium for PHE on MBC was achieved within 1.0 h. The maximum adsorption capacity of PHE on MBC was 97.6 mg g^-1 based on the analysis of the Sips model, which was significantly higher than that of other sources of BCs. The adsorption mechanism of the two BCs was mainly attributed to the action of surface functional groups and π-π-conjugated reactions. The adsorption of PHE on MBC mainly occurred in the functional groups of C-O and Fe₃O₄, but that on BC was mainly in the functional groups of -OH, N-H, C=C and C-O.

Inactivation of Laccase by the Attack of As (III) Reaction in Water

Laccase is a multicopper oxidase containing four coppers as reaction sites, including one type 1, one type 2, and two type 3. We here provide the first experimental data showing that As (III) can be effectively removed from water and transformed to As (V) through reactions mediated by laccase with the presence of oxygen. To this end, the As (III) removal, As (V) yields, total protein, active laccase, and copper concentrations in the aqueous phase were determined, respectively. Additionally, electron paramagnetic resonance spectra and UV-vis spectra were applied to probe possible structural changes of the laccase during the reaction. The data offer the first evidence that laccase can be inactivated by As (III) attack thus leading to the release of type 2 copper. The released copper has no reactivity with the As (III). These findings provide new ideas into a significant pathway likely to master the environmental transformation of arsenite, and advance the understanding of laccase inactivation mechanisms, thus providing a foundation for optimization of enzyme-based processes and potential development for removal and remediation of arsenite contamination in the environment.

Molecular Characterization of Fusarium Solani Degrades a Mixture of Low and High Molecular Weight Polycyclic Aromatic Hydrocarbons

Objectives:

This study evaluates the ability of a non-white rot fungus strain, HESHAM-1, to degrade a mixture of low (naphthalene and phenanthrene) and high (chrysene and benzo(a)pyrene) molecular weight polycyclic aromatic hydrocarbons (LMW and HMW PAHs).

Methods:

Strain HESHAM-1 was isolated from oil polluted soil by enrichment method using phenanthrene as the sole source of carbon and energy. The strain showed the ability to tolerate and degrade a mixture of both low and high molecular weight PAHs. In the presences of LMW-PAHs (naphthalene and phenanthrene) as co-substrate, chrysene and benzo(a)pyrene (HMW-PAHs) were, respectively degraded by the fungus strain HESHAM-1 which was confirmed by GC-MS analyses.

Results:

The degradation rate was found as 84.82% for naphthalene, 40.09% for phenanthrene, 57.84% for chrysene and 71.06% for benzo(a)pyrene at the end of 10 days. This is the first report describing the biodegradation of a mixture of four PAH compounds by non-white rot fungus strain HESHAM-1 isolated from Egyptian oil-polluted soil. The fungus strain HESHAM-1 was identified by morphological characteristics and molecular genetics technique based on PCR amplification and sequencing of the internal transcribed spacers (ITSs) of the rDNA region and intervening 5.8S rRNA gene. Blast result and phylogenetic analysis of gene sequencing suggested that strain HESHAM-1 was closely related toFusarium solaniwith 100% sequence identity.

Conclusion:

The present study clearly demonstrates that, strain HESHAM-1 could be used to remove the crude oil from the environment.

Enhanced performance of immobilized laccase in electrospun fibrous membranes by carbon nanotubes modification and its application for bisphenol A removal from water

Multi-walled carbon nanotubes (MWCNTs) were used as modified materials to improve the performance of laccase-carrying electrospun fibrous membranes (LCEFMs). The MWCNTs modified LCEFMs (MWCNTs-LCEFMs) were successfully fabricated via emulsion electrospinning, with active laccase and MWCNTs encapsulated inside the fibers. After modified by an optimal amount (1.5wt%, vs. polymer) of MWCNTs, the obtained MWCNTs-LCEFMs showed not only higher activity recovery (85.3%, vs. free laccase) than LCEFMs (71.2%), but also better storage and operational stability, which were mainly attributed to the promoted electron transfer in laccase-catalytic reaction. Furthermore, the specific surface area and tensile strength of MWCNTs-LCEFMs have also been enhanced nearly 2 and 3 times than those of LCEFMs, respectively. The MWCNTs-LCEFMs were applied to remove the widespread bisphenol A from water, where their removal efficiency reached above 90%, with the degradation efficiency accounting for over 80%, and their adsorption efficiency increased about 45% than that of LCEFMs. In addition, the endurances of MWCNTs-LCEFMs to environmental factors such as pH and temperature were also improved.

Laccase encapsulation in chitosan nanoparticles enhances the protein stability against microbial degradation

A novel concept with the result of enzyme stabilization against microbial degradation in real bioremediation processes was developed through the encapsulation of laccase in chitosan nanoparticles. Besides of abundant information on laccase-chitosan conjugates, we report the laccase encapsulation into nanoparticles based in chitosan. The chitosan-tripolyphosphate technique was applied for the production of morphologically homogeneous enzymatic nanoparticles, with high enzyme encapsulation efficiency, small asymmetric sizes (from 40 to 90 nm), and rough surfaces. Contrary to macroscopic immobilized enzymes, temperature and pH activity profiles of nano-sized laccase were similar to those of free enzyme. The substrate affinity constant (K M) of nano-encapsulated laccase was similar to these from free enzyme, while its activity rate constant (k cat) represented 60 % of these obtained with free enzyme. Importantly, stability of nano-encapsulated laccase against microbial degradation in soil, compost, and wastewater was significantly increased. After 24 h exposure to wastewater from a treatment plant, the laccase activity of the nanoparticles was 82.8 % of initial activity, compared with only 7.8 % retained activity for free enzyme. After 36 h incubation in compost extract, the laccase nanoparticles showed 72.4 % of the initial activity, while the free enzyme was almost completely inactivated. Finally, after 84 h incubation in soil extract, the nanoparticles and free preparations showed 57.9 and 17.3 % of the initial activity, respectively. Thus, the nanoencapsulation of enzymes able to transform pollutants is an alternative to improve the operational lifetime of enzymes in real environmental applications.

Polycyclic aromatic hydrocarbons (PAHs) removal by sorption: A review

Polycyclic aromatic hydrocarbons (PAHs) are organic micro pollutants which are persistent compounds in the environment due to their hydrophobic nature. Concerns over their adverse effects in human health and environment have resulted in extensive studies on various types of PAHs removal methods. Sorption is one of the widely used methods as PAHs possess a great sorptive ability into the solid media and their low aqueous solubility property. Several adsorbent media such as activated carbon, biochar, modified clay minerals have been largely used to remove PAHs from aqueous solution and to immobilise PAHs in the contaminated soils. According to the past studies, very high removal efficiency could be achieved using the adsorbents such as removal efficiency of activated carbon, biochar and modified clay mineral were 100%, 98.6% and >99%, respectively. PAHs removal efficiency or adsorption/absorption capacity largely depends on several parameters such as particle size of the adsorbent, pH, temperature, solubility, salinity including the production process of adsorbents. Although many studies have been carried out to remove PAHs using the sorption process, the findings have not been consolidated which potentially hinder to get the correct information for future study and to design the sorption method to remove PAHs. Therefore, this paper summarized the adsorbent media which have been used to remove PAHs especially from aqueous solutions including the factor affecting the sorption process reported in 142 literature published between 1934 and 2015.

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

Background

Marine 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.

Results

In 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.

Conclusions

Thirteen 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 material

The online version of this article (doi:10.1186/s12864-016-2445-4) contains supplementary material, which is available to authorized users.

Laccase mediated transformation of 17β-estradiol in soil

It is known that 17β-estradiol (E2) can be transformed by reactions mediated by some oxidoreductases such as laccase in water. Whether or how such reactions can happen in soil is however unknown although they may significantly impact the environmental fate of E2 that is introduced to soil by land application of animal wastes. We herein studied the reaction of E2 in a model soil mediated by laccase, and found that the reaction behaviors differ significantly from those in water partly because of the dramatic difference in laccase stability. We also examined E2 transformation in soil using (14)C-labeling in combination with soil organic matter extraction and size exclusion chromatography, which indicated that applied (14)C radioactivity was preferably bound to humic acids. The study provides useful information for understanding the environmental fate of E2 and for developing a novel soil remediation strategy via enzyme-enhanced humification reactions.

The removal of fluoranthene by Agaricus bisporus immobilized in Ca-alginate modified by Lentinus edodes nanoparticles

Fruiting bodies of Agaricus bisporus (A. bisporus) were entrapped in Ca-alginate modified by Lentinus edodes nanoparticles (CA-LENP) to adsorb and biodegrade fluoranthene (FLU) efficiently from an aqueous solution in a fluidized bed bioreactor.