Simultaneous Degradation Research Articles

Simultaneous efficient degradation and dechlorination of chloramphenicol using UV/sulfite reduction: Mechanisms and product toxicity

Chloramphenicol (CAP) is of great concern due to its extensive use and nonnegligible impact on the eco-environment. Herein, the degradation performance and mechanism of CAP by UV/sulfite advanced reduction processes (ARPs) were systematically investigated. 90.67 % degradation efficiency and 92.22 % dechlorination of CAP were simultaneously achieved within 50 min using UV/sulfite-ARPs. The degradation and dechlorination efficiency of the CAP remained elevated with the increase of sulfite concentration, and eventually complete degradation and dechlorination were achieved. Hydrated electrons (eaq−) and direct UV photolysis dominated in the degradation and dechlorination of CAP at pH 5–11. The presence of commonly co-existing anions, humic acid and various water matrices exhibited negligible effect on the CAP degradation and dechlorination efficiencies. Possible degradation pathways of CAP were proposed. Ecotoxicity prediction and seed germination experiments indicated that the acute and chronic ecotoxicity of CAP solution was significantly reduced after the treatment with UV/sulfite-ARPs. Overall, this study demonstrated that UV/sulfite-ARPs could be a promising approach for the CAP purification from wastewaters.

Achieving simultaneous hydrogen evolution and organic pollutants degradation through the modification of Ag3PO4 using Cs2AgBiBr6 quantum dots and graphene hydrogel

The Ag3PO4/Cs2AgBiBr6 quantum dots/graphene hydrogel (ACGH) photocatalytic system was designed. The Cs2AgBiBr6 quantum dots (CABBQDs) and graphene hydrogel (rGH) solved the insufficient redox ability and easy photocorrosion of Ag3PO4, at the same time, the novel system achieved full-spectrum-driven photoreforming to use for efficient photocatalytic hydrogen evolution and simultaneous organic compounds photodegradation. The feasibility study of alternative sacrificial agents evaluated higher simultaneous photocatalytic activity in tetracycline hydrochloride (TC) compared to general sacrificial agents (methanol, Na2S/Na2SO3, acid orange and glucose). The yield of hydrogen production and simultaneous photodegradation efficiency of TC were 5965.8 μmol/g and 98.32 % respectively in 6 h. And the hydrogen production rate in TC solution was more than twice that of general sacrificial agents within 24 h. Meanwhile, the mechanism exploration elucidated the photogenerated charge transfer path to generate the water splitting and photoinduced oxidizing species (h+, OH, ·O2-). The Hirshfeld atomic charges on TC and methanol molecules were calculated by density functional theory to predict the initial attack sites. Results indicated that the CCO and CNC fragments on TC molecules were inferred as nucleophilic attack and radical attack sites. And more electrons on TC could give to ACGH constantly for hydrogen production than methanol. The yield of hydrogen production and simultaneous degradation efficiency of TC remained at 3683.24 μmol/g and 93.22 % respectively in six photocatalytic cycle experiments, showing the reusability of ACGH. The simultaneous hydrogen production and degradation of organic pollutants of ACGH could proceed in actual municipal wastewater.

Optimization and biochemical characterization of a thermotolerant processive cellulase, PtCel1, of Parageobacillus thermoglucosidasius NBCB1.

Vermicomposting involves enrichment of microorganisms that are able to resist higher temperatures and perform simultaneous degradation of lignocellulose, and therefore, such microbial communities are a potential source of cellulolytic enzymes. This study aimed to optimize the production of a processive cellulase by Parageobacillus thermoglucosidasius NBCB1 isolated from vermicompost, under submerged fermentation of rice straw and to characterize the purified enzyme for industrial suitability. Cellulase production in basal medium (7.27 IU/mg) was enhanced to 61 IU/mg by One Factor At a Time approach, which was further improved to 78.46 IU/mg by genetic algorithm based artificial neural networking. The cellulase PtCel1 purified from bacterial culture showed a molecular weight of≈33 kD, had activity on both crystalline (305 IU/mg) and amorphous (184 IU/mg) cellulose as substrates. It had pH and temperature optima of 5.5°C and 60°C, respectively, and retained 100% activity upon preincubation at 60°C for 1 h indicating thermostability. PtCel1 was tolerant to sodium dodecyl sulfate, glucose and mannose; and the various metal chlorides, such as sodium, magnesium, calcium and zinc, acted as inducers giving 77.54%, 45.15%, 61.10%, and 169.14% augmentation of activity, respectively. Its efficiency on cellulosic substrates and robustness against aforementioned chemical and thermal environment makes it suitable for industrial applications.

Comparative study of dihydroxybenzene isomers degradation and bioelectricity generation using CuO as cathodic catalyst in double chambered microbial fuel cell

A double chambered microbial fuel cell (MFC) showed enormous capacity in the simultaneous degradation of synthetic wastewater and dihydroxybenzene isomers (catechol, resorcinol and hydroquinone) and concurrently with bioelectricity generation. Operating parameter such as effect of catalyst on MFC system was evaluated using bare carbon plate and copper (II) oxide (CuO) loaded carbon plate as cathodes, respectively, in terms of chemical oxygen demand (COD) and dihydroxybenzene isomers removal efficiency, maximum voltage output and power density. Results revealed that the application of CuO loaded carbon plate was more effective in the COD removal of synthetic wastewater in the anodic chamber and degradation of dihydroxybenzene isomers in the cathodic chamber. Compared with the bare carbon plate as cathode, the COD removal efficiency of synthetic wastewater, removal rate of dihydroxybenzene isomers and maximum voltage output increased 20, 100 and 31 %, respectively, when CuO was applied as cathodic catalyst. Among the dihydroxybenzene isomers, hydroquinone exhibited the best performance in both absence and presence of catalyst in the MFC. The position of the substituent of hydroxyl groups possessed significant effect on the reaction rate, reactivity and conductivity of dihydroxybenzene isomers. Hydroquinone was more susceptible to be degraded than that of catechol and resorcinol due to its lower dipole moment which eased the bond cleavage. The intermediate products of degradation of catechol, resorcinol and hydroquinone were determined using gas chromatograph-mass spectrometer and the degradation pathways were proposed.

Simultaneous remediation of three neonicotinoids in soil using nanoscale zero-valent iron-activated persulfate process: Performance, effect of process parameters, and mechanisms

Neonicotinoids are commonly used pesticides in agricultural regions all over the world, and their widespread use has caused potential environmental pollution issues in recent years. The simultaneous degradation of three representative neonicotinoids (i.e., imidacloprid (IMI), thiamethoxam (TMX) and dinotefuran (DIN)) in soil by a nanoscale zero-valent iron-activated persulfate (nZVI-activated PS) process was investigated. Under the optimum conditions with 1 mg g−1 nZVI, 10 mM PS at an initial pH value of 6.9 and a water-soil ratio of 1.5, the degradation efficiency of IMI, TMX and DIN reached 89%, 86% and 69% in 15 mins, respectively. Degradation of the three neonicotinoids was fitted with a pseudo first-order kinetic model. High nZVI dosage and PS concentration were found to enhance the neonicotinoids degradation. In contrast, the presence of Cl-, HCO3- and HA reduced the degradation rates of the three neonicotinoids. Soil physicochemical properties showed a significant effect on the degradation efficiencies of the three neonicotinoids. In addition, quenching experiments combined with electron paramagnetic resonance (EPR) showed that free radicals SO4•- and •OH contributed to the degradation of three neonicotinoids in the nZVI-activated PS system. Degradation pathways were proposed based on identified intermediates of IMI, TMX and DIN. Overall, the nZVI-activated PS process is an effective method for remediation of the neonicotinoids contaminated soil.

Metagenomic analysis of microbial community and gene function of anodic biofilm for nonylphenol removal in microbial fuel cells

Nonylphenol as a high priority control of persistent toxic contaminant has been frequently detected in environment. In this study, Dual-chamber microbial fuel cells (MFCs) were constructed for simultaneous nonylphenol degradation and electricity generation; and microbial community and gene function of anodic biofilm were analyzed through metagenomic sequencing. The results showed that nonylphenol removal rate reached 82% within 60 h in MFCs, and the maximum voltage achieved 0.60 V when the external resistance was 1000 Ω. Metagenomics analysis showed that Proteobacteria and Actinobacteria were dominant phyla in biofilm attached to anode. At genus level, the relative abundance of Streptomyces (21.45%), Microbacterium (11.96%), Burkholderia (10.90%), Pusillimonas (7.59%), Stenotrophomonas (6.62%), Pseudomonas (4.44%), Nitrospirillum (3.75%), Nocardia (1.73%), Arthrobacter (1.71%) and Bacillus (1.21%) were remarkably higher than those of control groups. In terms of functional genes annotation, a relatively high gene number was focus on various metabolic pathways (such as carbon metabolism, riboflavin metabolism, and nitrogen metabolism) during MFCs operated. The metabolic pathways of nonylphenol were suggested to divide into the oxidation of aromatic ring (route-1) and the fission of alkyl chain (route-2) based on KEEG analysis.

Controlled alcoholysis of PET to obtain oligomers for the preparation of PET-PLA copolymer

Controlled degradation of macromolecules or natural macromolecules is important for their subsequent utilization. Normally, it is easier to degrade them to monomers than to oligomers in designated molecular weight range, the controlled degradation is much difficult to achieve and has been challenge for the utilization of macromolecules. Here, we proposed a strategy for simultaneous degradation of the inner and outer layers of PET, which avoid the degradation of polymers from the outside to the inside and achieved the controlled degradation. Under high temperature and micro-pressure conditions, PET is transformed from dense to flocculent structure by the swelling effect, which satisfies the need for simultaneous degradation of the inner and outer layers. In addition, a stable “Dawson” type Polyoxometalates (POMs) α2-K8P2W17O61X(H2O)‧16H2O (X = Zn, Mn, Co, Ni, Cu) with limited number of catalytic activity center was synthesized and applied to PET alcoholysis to obtain oligomer with given molecular weight range. Under the optimal conditions, PET: EG: POM catalyst = 1.0: 4.0: 0.02 (wt%), 240 °C, 10 min, PET was completely degraded and obtained the oligomer products (Mn < 2000 g/mol) with 72.1 % yield. By investigating the mechanism of the controlled alcoholysis, the formation of flocculent PET was be the key factor in achieving controlled degradation; hydrogen bonding and coordination of POMs are the key interactions to achieve rapid alcoholysis. Finally, oligomers were applied in the preparation of PET-PLA copolymers to follow sustainable route. The incorporation of bio-based polymers demonstrates better inclusiveness to the environment and contributes to harmonious development.

Titania Thin Film Coated Glass for Simultaneous Ammonia Degradation and UV Light Blocking Layer in Photovoltaics

In this work, we have investigated the potential dual application of TiO2 thin films as a photocatalyst for ammonia degradation, and as a UV light blocking layer in c-Si photovoltaics. For this purpose, we deposited a series of TiO2 thin films on a glass substrate by reactive magnetron sputtering and analysed the influence of the deposition parameters (O2/Ar working gas content and pressure) on the structural, optical and photocatalytic properties. All samples are nanocrystalline anatase TiO2 and have a uniform surface (RMS roughness &lt; 5 nm) in a wide range of magnetron sputtering deposition parameters. They are transparent in the Vis/NIR spectral range and strongly absorb light in the UV range above the optical bandgap energy (3.3 eV), which makes them suitable for the use as UV blocking layers and photocatalysts. The photocatalytic properties were studied in a mini-photocatalytic wind tunnel reactor by examining ammonia degradation. A kinetic study was performed to estimate the reaction rate constants for all samples. The intrinsic reaction rate constant confirmed the crucial role of surface morphology in ammonia decomposition efficiency.

Green and sustainable 'Al-Zr-oligosaccharides' tanning agents from the simultaneous depolymerization and oxidation of waste paper.

Developing chrome-free and sustainable tanning agents is extremely important to the sustainability of the leather industry. Herein, we have synthesized an Al-Zr-oligosaccharides tanning agent via a simultaneous degradation and oxidation of cellulose in waste paper. The influence of the temperature and the concentrations of AlCl3 and H2O2 during the synthesis were thoroughly investigated on the properties of the tanning agent and the leather produced. The synthesis temperature and the concentration of AlCl3 were the factors primarily affecting the effective depolymerization of cellulose. They controlled the conversion of waste paper into oligosaccharides with an appropriate molecular weight to efficiently penetrate the leather matrix. In parallel, the H2O2 concentration substantially influenced the tanning performance of the Al-Zr-oligosaccharides, diminishing the chromaticity of the tanning liquid via oxidation and promoting the conversion of C2/C3/C6-OH moieties into -CHO/-COOH. These functional groups increased the surface charge of the oligosaccharides allowing more effective coordination with Al/Zr, which facilitated the penetration of Al/Zr species into the leather matrix. Once inside the leather matrix, Al and Zr were released and reacted with the collagen fibers in leather, which resulted in effective leather tanning. The process optimization revealed that up to 57% of waste paper could be converted into a low-chromaticity (4350 AU) liquid hydrolysate with the synthesis conducted at 177 °C in a system comprising 47 mM AlCl3 and 5 vol% H2O2. The application of this liquid for tanning provided leather with a shrinkage temperature (86.5 °C) sufficiently high for commercial applications. These excellent results, combined with the intrinsic green nature of our approach, exemplify a step forward to simultaneously reduce pollution and hazards in leather industries giving a second life to waste paper.

Characterization of the simultaneous degradation of pyrene and removal of Cr(VI) by a bacteria consortium YH

Microorganisms that can simultaneously remediate organic pollutants and heavy metal contamination are great significance in bioremediation. Nevertheless, reports of such microorganisms are still scarce. Here, Pseudomonas sp. YH-1 and Rhodococcus sp. YH-3 were isolated and identified, and they showed greater tolerance to hexavalent (VI) (750 and 800 mg·L−1). The constructed bacteria consortium YH (YH-1:YH-3 = 1:1) could simultaneously degrade 41.69% of pyrene (50 mg·L−1) and remove 76.67% of Cr(VI) (30 mg·L−1) within 5 days. The potential mechanism of Cr(VI) tolerance of YH was further explored by genomic and microscopic analysis. The results showed that YH responded to Cr(VI) stress mainly through efflux of Cr(VI) by chrA and copZ, chromate reduction, DNA-repaired proteases reduces ROS damage, and biosorption by carboxyl, hydroxyl, amino functional groups. Strains YH-1 and YH-3 also contained a variety of genes associated with resistance to other heavy metals, such as cadmium (czcBD), mercury (merAPTR), manganese (mntABC) and copper (copAC, cusABRF and pcoBD). Based on GC–MS and genomic analysis, pyrene was degraded via salicylic acid and phthalic acid pathways. Moreover, a great number of genes related to aromatic hydrocarbon catabolism were identified in the genomes of YH-1 and YH-3. These results confirmed the potential application of the bacteria consortium YH in the bioremediation of water and soil co-contaminated with PAHs-heavy metals.

Maximizing electron flux, microbial diversity and gene abundance in MFC powered electro-Fenton system by optimizing co-addition of lysozyme and 2-bromoethanesulfonate

In this study, a microbial fuel cell powered electro-Fenton system (MFCⓅEFs) was established in order to overcome the shortcomings of low electron flux and unexpected methane production, while simultaneously treating excess sludge (ES, substrate) and refractory syringic acid (SA). A strategy of co-adding lysozyme (LZ, as ES degradation catalyst) and 2-bromoethanesulfonate (BES, as methane inhibitor) into ES was optimized in MFCⓅEFs to maximize electron flux, microbial community diversity and functional gene abundance. The removal of sludge total chemical oxygen demand (TCOD) achieved 81.69% in 25 d under an optimal co-addition strategy (40.41 mg/gSS of LZ, 27.03 mmol/L of BES, adding on 22.8 h of the7th day), with a simultaneous high degradation of SA (99.30% in 25 h). Correspondingly, a maximum power density of 3.35 W/m3 was achieved (only 0.62 W/m3 from the control), which effectively realizes in-situ micro-electricity generation and utilization for bioelectric Fenton processes. Moreover, 42.25% of the total charges were employed for bio-electricity generation. The electricigens of Pseudomonas, Acinetobacter and Chlorobium showed effective enrichment, while the abundance of methanogenesis archaea was extremely decreased. Functional genes associated with methanogenesis including mtaA, hdra, and mcrA were effectively inhibited. The life cycle assessment along with an optimized co-addition strategy illustrated a beneficial environmental effect, particularly in terms of ecosystem quality and climate change. Above all, an enhanced synchronous degradation of excess sludge and refractory pollutants had been realized in a green and environmentally friendly way.

Fenton-like oxidation mechanism for simultaneous removal of estriol and ethinyl estradiol by green synthesized Mn3O4 NPs

Manganese tetroxide (Mn3O4) nanomaterials were prepared by green tea extract and applied to catalyze sodium peroxydisulfate (PDS) for the simultaneous degradation of estriol/17a-ethinylestradiol (E3/EE2) with removal efficiencies of 97.5 and 96.4% for E3 and EE2, respectively. XPS also showed that before and after the reaction the divalent manganese content decreased from 50.2 to 34.8%, indicating divalent manganese plays a major role in the catalytic process. EPR quenching and electrochemical studies showed that while initially singlet oxygen (1O2), sulfate (SO4•-), superoxide (O2•-) and hydroxyl (•OH) radicals were all generated in the system, thereafter, the oxidation of E3/EE2 mainly depended on 1O2 and O2•-, where O2•- intermediates participated in the generation of 1O2 in the Fenton-like process. LC-MS analysis showed that degradation products of E3/EE2 were mainly produced via hydroxyl and sulfate degradation pathways. Finally, a mechanism of Fenton-like oxidation of E3/EE2 was proposed.

Efficient organic contaminant and Cr (VI) synchronous removing by one-step modified molybdenite cathode microbial fuel cells.

As a novel technique with a wide range of applications, microbial fuel cell (MFC) could simultaneously remove organic contaminants and heavy metals in complex wastewater, despite striking differences in physicochemical properties of these contaminant. But its wastewater treatment efficiency is restricted by its lower generation performance. However, approaches for the modification of MFCs' cathode with appropriate catalyst could effectively overcome this limitation. Herein, a new-type efficient cathode catalyst was invented through modifying natural molybdenite via one-step oxidation method. In this case, molybdenite had many changes in morphology (wave-shaped bending, fragmentation and decrescent diameter) during oxidation modification process, and oxidation-modified molybdenite could provide much more active sites for the cathode. After applying this novel cathode catalyst, the electric generation capacity of MFC system increased by 5.08 times, and its simultaneous degradation efficiency of methyl blue (MB) and Cr (VI) increased by 3.35 times (compared with graphite cathode MFC). This study provides a novel low-carbon and environmentally friendly way to prepare high efficiency cathode catalyst materials and provides a new idea of simultaneous purification for organic and metallic pollutants from complex wastewater.

Purification mechanism of corona discharge coupled with dimethyl sulfoxide microemulsion for simultaneous desulfurization and denitrification

In this study, a new absorbent dimethyl sulfoxide (DMSO) microemulsion is used, and corona discharge coupled with dimethyl sulfoxide microemulsion is proposed for simultaneous desulfurization and denitrification. This study solves the problem of low efficiency of simultaneous SO2 and NO purification and avoids the problem of easy poisoning of catalysts for simultaneous desulfurization and denitrification. In addition, it makes up for the defects of low efficiency and complex products of desulfurization and denitrification by plasma alone. In this study, the effects of different corona discharge voltages, DMSO microemulsion oil–water ratio and oxygen concentration on the simultaneous removal of SO2 and NO were investigated in detail. The study showed that increasing the voltage and oxygen concentration had a significant promotion effect on the degradation of NO, but the high oxygen concentration would release part of the captured SO2. Under the best experimental conditions, the SO2 removal efficiency could reach 93.4 % and the NO removal efficiency was 84.9 %. In addition, the adsorption energy calculations combined with different initial concentrations and different DMSO microemulsion temperatures illustrate that SO2 and NO react competitively with SO bonds in DMSO and OH bonds in isoamyl alcohol in DMSO microemulsions, with SO2 being preferentially adsorbed. Finally, this study explains in detail the mechanism of simultaneous SO2 and NO degradation, showing that the reactive species generated during corona discharge can excite microemulsions to produce more reactive radicals and active substances to further improve the removal of SO2 and NO.

Electric field enhanced heterogeneous Fenton reaction: simultaneous pollutant degradation and catalyst reactivation

AbstractBACKGROUNDTraditional Fe‐based heterogeneous Fenton catalysts have the problem of a low generation rate of Fe(II) from Fe(III), and this leads to poor reaction efficiency and catalyst deactivation. In this work, Fe3O4@N‐MWCNT catalyst with both strong magnetism and high electrical conductivity was synthesized. In addition, a novel unibody degradation‐reactivation reactor was designed for simultaneous pollutant degradation and catalyst reactivation.RESULTSThe X‐ray Diffraction (XRD) patterns and Scanning Electron Microscope (SEM) images reveal the great dispersity of Fe3O4 loaded on oxidized‐MWCNT. The Vibrating Sample Magnetometer (VSM) tests and electrochemical characterization confirmed the strong magnetism, high electrical conductivity, and good capacitance performance of the catalyst. The optimum condition of heterogeneous Fenton degradation experiments was investigated. A favorable recovery of Fe(II) was confirmed through the detection of the Fe(II): Fe(III) ratio from X‐ray Photoelectron Spectroscopy (XPS) characterization.CONCLUSIONThe combination of Fe3O4 and MWCNT can significantly increase the heterogeneous Fenton catalytic activity of the catalyst. Under the assistance of a finely controlled flow pattern and an applied magnetic field, three different processes (including heterogeneous Fenton reaction, electrochemical oxidation, and catalyst reactivation) were joined organically into a synergistic reaction system. It is demonstrated that the catalyst can replenish the sacrificed electrons during the reactivation process and improve its cycling performance. © 2022 Society of Chemical Industry (SCI).

Lignocellulosic biomass based microbial fuel cells: Performance and applications

Lignocellulosic biomass has the potential to replace fossil fuels as a sustainable and renewable feedstock for energy generation . Microbial fuel cell technology offers an energy-producing system from lignocellulosic biomass. This review explores different microbial fuel cell designs i.e. membrane-less single chambered, double chambered and integrated microbial fuel cell along with their mode of operation. There are some compatibility issues with different microbial fuel cell designs in utilizing the lignocellulosic biomass as feed. Microbial fuel cell setup with integrated pre-treatment or simultaneous degradation of lignocellulosic biomass may provide a solution. A careful selection of microbial community according to the microbial fuel cell operation conditions along with upscaling of the system may help in efficient utilization of renewable energy sources . Thus, lignocellulosic biomass-based microbial fuel cell may potentially be used in the bioremediation, production of biofuels and industrially important value-added products along with simultaneous production of electricity. • Lignocellulosic biomass may be used as a renewable feedstock in microbial fuel cells. • Microbial fuel cell designs influence the substrate utilization efficiency. • Pre-treatment of lignocellulosic biomass is required to be used as feed. • Such eco-friendly technology may be used for several applications.

CdS-based artificial leaf for photocatalytic hydrogen evolution and simultaneous degradation of biological wastewater.

Rational design of all-solid-state Z-scheme heterojunction with advanced structure is essential for boosting photocatalytic efficiency. Herein, we design and fabricate a novel Z-scheme photocatalyst with leaf architecture (named artificial leaf) via a simple dipping-calcination (DC) process followed by a successive ionic layer adsorption and reaction (SILAR) strategy. The prepared artificial leaf, composing of CdS, InVO4, and BiVO4, holds advanced leaf-like structure and Z-scheme electron transfer pathway. As a result, this novel artificial leaf exhibits outstanding capability for the harvesting of visible light and superior efficiency for the separation of photogenerated electron-hole pairs, as well as remarkably enhanced photocatalytic performance and stability for H2 evolution (with the rate of 5033μmg-1∙h-1) and pollution degradation (46% pollution can be degraded within 3h).

Degradation of corn starch with different moisture content by gaseous hydrogen chloride

Corn starch, subjected to solid-state degradation using gaseous hydrogen chloride, was characterized to investigate the parameter effects on starch properties and further explore the thermal behavior of inter-crystalline amorphous lamellae of starch. The obtained starch granules exhibited A-type polymorph with 75–98 % recovery (w/w). Degreasing moisture content (6–12 %) with increasing duration (1–8 h) and temperature (25–45 °C) progressively decreased the weight-average degree of polymerization to 55–75 anhydroglucose unit and increased the gelatinization temperature range. However, starch degraded at 6 % moisture and 25 °C exhibited much higher polydispersity index than those degraded at 9–12 % moisture, accompanied by the decreased start but comparable onset gelatinization temperatures. This thermodynamic difference was inherent but diminished gradually with increasing degradation temperature. These findings suggest that the degradation at 9–12 % moisture starts from the bulk amorphous region of starch then sequentially reaches its inter-crystalline amorphous lamellae, while the simultaneous degradation of both regions is for starch with 6 % moisture.

Expression of phenylalanine ammonia lyase as an intracellularly free and extracellularly cell surface-immobilized enzyme on a gut microbe as a live biotherapeutic for phenylketonuria.

Phenylketonuria (PKU), a disease resulting in the disability to degrade phenylalanine (Phe) is an inborn error with a 1 in 10,000 morbidity rate on average around the world which leads to neurotoxicity. As an potential alternative to a protein-restricted diet, oral intake of engineered probiotics degrading Phe inside the body is a promising treatment, currently at clinical stage II (Isabella, et al., 2018). However, limited transmembrane transport of Phe is a bottleneck to further improvement of the probiotic’s activity. Here, we achieved simultaneous degradation of Phe both intracellularly and extracellularly by expressing genes encoding the Phe-metabolizing enzyme phenylalanine ammonia lyase (PAL) as an intracellularly free and a cell surface-immobilized enzyme in Escherichia coli Nissle 1917 (EcN) which overcomes the transportation problem. The metabolic engineering strategy was also combined with strengthening of Phe transportation, transportation of PAL-catalyzed trans-cinnamic acid and fixation of released ammonia. Administration of our final synthetic strain TYS8500 with PAL both displayed on the cell surface and expressed inside the cell to the PahF263S PKU mouse model reduced blood Phe concentration by 44.4% compared to the control EcN, independent of dietary protein intake. TYS8500 shows great potential in future applications for PKU therapy.Supporting InformationThe supporting information is available online at 10.1007/s11427-021-2137-3. The supporting materials are published as submitted, without typesetting or editing. The responsibility for scientific accuracy and content remains entirely with the authors.

Intensified fish farming. Performance of electrochemical remediation of marine RAS waters

Aquaculture has been the fastest growing agricultural sector in the past few decades and currently supplies about half of the fish market. A range of environmental and management concerns including limited land and water availability have led to intensifying fish production by recirculating aquaculture systems (RAS). Fish's diet contains 30–60 % protein and about 4–10 % nitrogen (N). As fish assimilate only 20–30 % of the feed to produce body mass, the unassimilated N is released in the form of toxic ammonium that deteriorates water quality and compels its degradation. Widely extended biological nitrification is not efficient in the removal of nitrites nor other chemicals and pharmaceuticals used during fish culture. Electrochemical oxidation, a less developed alternative, reports several advantages such as, i) simultaneous degradation of ammonia‑nitrogen (TAN) and water disinfection in the same step with considerable simplification of the whole process, ii) easy adaptability to different production scales and periods of fish growth, and iii) no generation of harmful by-products and no use of chemicals, among others. Besides, in the case of marine aquaculture, the technology benefits from the high conductivity of seawater; thus, electrochemical oxidation is positioned in a very good place to satisfy the water treatment needs of the increasing production rate of marine aquaculture fish. Here, we report the analysis of the performance of a RAS demonstration plant aimed at farming gilthead sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) and provided with electrochemical remediation of culture water. The performance of the plant, with 20 m3 of seawater operating at a recirculation rate of 0.9–1.4 h−1, has been analysed in terms of TAN removal, water disinfection, make-up water intake and energy consumption and compared to data of conventional RAS provided with biofilters. The benefits and advantages of the innovative electrochemical remediation of RAS water are highlighted.