Biodegradation and Mineralization of Polystyrene by Plastic-Eating Mealworms: Part 1. Chemical and Physical Characterization and Isotopic Tests.

Polystyrene (PS) is generally considered to be durable and resistant to biodegradation. Mealworms (the larvae of Tenebrio molitor Linnaeus) from different sources chew and eat Styrofoam, a common PS product. The Styrofoam was efficiently degraded in the larval gut within a retention time of less than 24 h. Fed with Styrofoam as the sole diet, the larvae lived as well as those fed with a normal diet (bran) over a period of 1 month. The analysis of fecula egested from Styrofoam-feeding larvae, using gel permeation chromatography (GPC), solid-state (13)C cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR) spectroscopy, and thermogravimetric Fourier transform infrared (TG-FTIR) spectroscopy, substantiated that cleavage/depolymerization of long-chain PS molecules and the formation of depolymerized metabolites occurred in the larval gut. Within a 16 day test period, 47.7% of the ingested Styrofoam carbon was converted into CO2 and the residue (ca. 49.2%) was egested as fecula with a limited fraction incorporated into biomass (ca. 0.5%). Tests with α (13)C- or ß (13)C-labeled PS confirmed that the (13)C-labeled PS was mineralized to (13)CO2 and incorporated into lipids. The discovery of the rapid biodegradation of PS in the larval gut reveals a new fate for plastic waste in the environment.

Biodegradation and Mineralization of Polystyrene by Plastic-Eating Mealworms: Part 2. Role of Gut Microorganisms.

The role of gut bacteria of mealworms (the larvae of Tenebrio molitor Linnaeus) in polystyrene (PS) degradation was investigated. Gentamicin was the most effective inhibitor of gut bacteria among six antibiotics tested. Gut bacterial activities were essentially suppressed by feeding gentamicin food (30 mg/g) for 10 days. Gentamicin-feeding mealworms lost the ability to depolymerize PS and mineralize PS into CO2, as determined by characterizing worm fecula and feeding with (13)C-labeled PS. A PS-degrading bacterial strain was isolated from the guts of the mealworms, Exiguobacterium sp. strain YT2, which could form biofilm on PS film over a 28 day incubation period and made obvious pits and cavities (0.2-0.3 mm in width) on PS film surfaces associated with decreases in hydrophobicity and the formation of C-O polar groups. A suspension culture of strain YT2 (10(8) cells/mL) was able to degrade 7.4 ± 0.4% of the PS pieces (2500 mg/L) over a 60 day incubation period. The molecular weight of the residual PS pieces was lower, and the release of water-soluble daughter products was detected. The results indicated the essential role of gut bacteria in PS biodegradation and mineralization, confirmed the presence of PS-degrading gut bacteria, and demonstrated the biodegradation of PS by mealworms.

Evidence of polyethylene biodegradation by bacterial strains from the guts of plastic-eating waxworms.

Polyethylene (PE) has been considered nonbiodegradable for decades. Although the biodegradation of PE by bacterial cultures has been occasionally described, valid evidence of PE biodegradation has remained limited in the literature. We found that waxworms, or Indian mealmoths (the larvae of Plodia interpunctella), were capable of chewing and eating PE films. Two bacterial strains capable of degrading PE were isolated from this worm's gut, Enterobacter asburiae YT1 and Bacillus sp. YP1. Over a 28-day incubation period of the two strains on PE films, viable biofilms formed, and the PE films' hydrophobicity decreased. Obvious damage, including pits and cavities (0.3-0.4 µm in depth), was observed on the surfaces of the PE films using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The formation of carbonyl groups was verified using X-ray photoelectron spectroscopy (XPS) and microattenuated total reflectance/Fourier transform infrared (micro-ATR/FTIR) imaging microscope. Suspension cultures of YT1 and YP1 (10(8) cells/mL) were able to degrade approximately 6.1 ± 0.3% and 10.7 ± 0.2% of the PE films (100 mg), respectively, over a 60-day incubation period. The molecular weights of the residual PE films were lower, and the release of 12 water-soluble daughter products was also detected. The results demonstrated the presence of PE-degrading bacteria in the guts of waxworms and provided promising evidence for the biodegradation of PE in the environment.

Cloud point extraction-flame atomic absorption spectrometry method for preconcentration and determination of trace cadmium in water samples.

A method based on cloud point extraction (CPE) separation/preconcentration of trace cadmium (Cd) as a prior step to its determination by flame atomic absorption spectrometry has been developed. Cadmium reacted with 8-hydroxyquinoline to form hydrophobic chelates, which were extracted into the micelles of nonionic surfactant oligoethylene glycol monoalkyl ether (Genapol X-080) in an alkaline medium. Octanol was used to depress the cloud point of Genapol X-080 in the extraction process. The chemical variables that affect the CPE, such as pH of complexation reaction, amount of chelating agent, Genapol X-080 and octanol were evaluated and optimized. Under optimized conditions, linearity was obeyed in the range of 10-500 µg/L, with the correlation coefficient of 0.9993. For 5 mL of sample solution, the enhancement factor was about 20. The limit of detection and limit of quantification of the method were 0.21 and 0.63 µg/L, respectively. The relative standard deviations (n = 6) was 3.2% for a solution containing 100 µg/L of Cd. The accuracy of the preconcentration system was evaluated by recovery measurements on spiked water samples. Recoveries of spiked samples varied in the range of 94.1-103.8%.

Synthesis, structure, and photoluminescent properties of metal-organic coordination polymers assembled with bithiophenedicarboxylic acid.

Four novel metal-organic coordination polymers with the formulas Mn(3)(btdc)(3)(DMF)(4) (1), Co(btdc)(DMF)(3) (2), Zn(btdc)(DMF)(3) (3), and Zn(btdc)(4,4'-bpy)(0.5) (4), where H(2)btdc = 2,2'-bithiophene-5,5'-dicarboxylic acid, DMF = N,N'-dimethylformamide, and 4,4'-bpy = 4,4'-bipyridine, have been successfully synthesized. Crystal 1 with Mn(2+) as the cation features a three-dimensional (3D) infinite framework built from trimanganese clusters, and crystals 2 and 3 with Co(2+) and Zn(2+), respectively, as the cation both have one-dimensional zigzag polymeric coordination chains. Crystal 4 synthesized using a mixture of 4,4'-bpy and H(2)btdc exhibits a triply interpenetrating 3D framework built from a dizinc paddlewheel second building unit with a distorted primitive cubic single net. The results of UV/vis spectra indicate that metal binding does not disturb the detailed electronic structure of the ligand. We also demonstrate that Zn(2+) can greatly enhance the luminescence emission of the H(2)btdc ligand, and the emission intensity of crystal 4 is almost 20 times higher than that of the free H(2)btdc ligand. Steady-state and time-resolved spectroscopic measurement reveal that the more rigid environment of the btdc ligand can stabilize the highly excited long-lived states in metal-organic frameworks (MOFs), which thus greatly changes the emission properties of MOFs.

The impact of pegylated recombinant human growth hormone replacement therapy on glucose and lipid metabolism in children with growth hormone deficiency.

BACKGROUND: This study aimed to investigate the impact of pegylated recombinant human growth hormone (PEG-rhGH) replacement therapy on glucose and lipid metabolism in children with growth hormone deficiency (GHD). METHODS: A total of 17 children with a growth hormone deficiency were treated with PEG-rhGH (trade name Juyi' Erchun) via subcutaneous injection once a week before sleep for 3 months. The doses given were 0.2 and 0.15 mg/(kg·week). The injection sites included the upper arm, the front of the thigh, and the periumbilical area of the abdominal wall. Follow-ups were conducted every 3 months after the treatment to detect the metabolic indexes of the children's blood glucose and blood lipids. Growth and development indexes, thyroid function, and other indexes were also detected regularly. The glucose and lipid metabolism indexes of each child, including fasting blood glucose, glycosylated hemoglobin, fasting insulin, total cholesterol, triglycerides, high-density lipoprotein (HDL), and low-density lipoprotein (LDL), were measured before the treatment and every three months after the treatment. The total detection time was 3-30 months. RESULTS: No significant differences in fasting blood glucose, glycosylated hemoglobin, fasting insulin, total cholesterol, triglycerides, HDL, and LDL were detected after the treatment when compared with measurements taken before the treatment (P>0.05). CONCLUSIONS: PEG-rhGH replacement therapy may have no significant impact on glucose and lipid metabolism in children with GHD. However, this conclusion needs to be verified through studies with larger samples and long-term follow-up periods.

Water-stable Cd(ii)/Zn(ii) coordination polymers as recyclable luminescent sensors for detecting hippuric acid in simulated urine for indexing toluene exposure with high selectivity, sensitivity and fast response.

Three novel Cd(ii)/Zn(ii) coordination polymers (CPs), namely [Cd(L)(BPDC)0.5H2O]·0.5H2O (1), [Zn2(L)2(BPDC)]·2H2O (2) and [Cd2(L)(BTC)H2O]·3H2O (3) (L = 4-(tetrazol-5-yl)phenyl-4,2':6',4''-terpyridine, H2BPDC = 4,4'-biphenyldicarboxylic acid, and H3BTC = 1,3,5-benzenetricarboxylic acid), have been successfully synthesized and characterized. CP 1 and CP 2 display new two-dimensional double-layered honeycomb frameworks containing uncoordinated nitrogen atoms from pyridine and tetrazole rings, which can easily form hydrogen bonds with various analytes. CP 3 exhibits a 3D framework also with uncoordinated nitrogen atoms from pyridine and tetrazole rings. The fluorescence explorations indicate that CPs 1-3 exhibit strong blue luminescence and excellent chemical stability under a relatively wide range of pH conditions. It is worth noting that CPs 1-3 can quantitatively detect hippuric acid (HA), which is a metabolite of toluene in human urine, with high selectivity, sensitivity, fast response and relatively low detection limits. Moreover, the sensing mechanism of CPs 1-3 for HA can mainly be ascribed to fluorescence resonance energy transfer (FRET). CPs 1-3 could be ideal candidates as HA sensors in human urine samples for practical applications. Notably, to the best of our knowledge, we report for the first time Cd(ii)/Zn(ii)-based luminescent sensors for detecting HA in simulated urine.

Enzyme-Adsorbed Chitosan Nanogel Particles as Edible Pickering Interfacial Biocatalysts and Lipase-Responsive Phase Inversion of Emulsions.

Here, a simple food-grade Pickering emulsion system is prepared and adopted for biphasic biocatalytic reactions. The chitosan nanogels were prepared with strong dispersion of chitosan aggregates approaching neutral pH and then used as the particle emulsifiers to produce oil-in-water Pickering emulsions. The chitosan nanogel exhibited high affinity to negatively charged lipase. As a result of increasing the biphasic interfacial area and loading amount on the oil-water interface, the catalysis activity of lipase and recycling and pH stability were highly enhanced through colorimetric determination of p-nitrophenol (the hydrolysis product of p-nitrophenyl palmitate). A general strategy was proposed to obtain stimulus-responsive Pickering emulsions that can undergo phase inversion. The in situ modification of the wettability of chitosan nanogel could be attributed to the interaction between nanogel and free fatty acids, which was triggered by lipase hydrolysis. This would permit a rapid and controlled release of hydrophobic active components in response to enzymatic triggers.

Development of a cloud point extraction and spectrophotometry-based microplate method for the determination of nitrite in human urine and blood.

A novel and simple method for the sensitive determination of trace amounts of nitrite in human urine and blood has been developed by combination of cloud point extraction (CPE) and microplate assay. The method is based on the Griess reaction and the reaction product is extracted into nonionic surfactant Triton-X114 using CPE technique. In this study, decolorization treatment of urine and blood was applied to overcome the interference of matrix and enhance the sensitivity of nitrite detection. Multi-sample can be simultaneously detected thanks to a 96-well microplate technique. The effects of different operating parameters such as type of decolorizing agent, concentration of surfactant (Triton X-114), addition of (NH4)2SO4, extraction temperature and time, interfering elements were studied and optimum conditions were obtained. Under the optimum conditions, a linear calibration graph was obtained in the range of 10-400 ng mL(-1) of nitrite with limit of detection (LOD) of 2.5 ng mL(-1). The relative standard deviation (RSD) for determination of 100 ng mL(-1) of nitrite was 2.80%. The proposed method was successfully applied for the determination of nitrite in the urine and blood samples with recoveries of 92.6-101.2%.

Complete genome sequence of Bacillus sp. YP1, a polyethylene-degrading bacterium from waxworm's gut.

Bacillus sp. strain YP1, isolated from the gut of waxworm (the larvae of Plodia interpunctella) which ate polyethylene (PE) plastic, is capable of degrading PE and utilizing PE as sole carbon source. Here we report the complete genome sequence of strain YP1, which is relevant to polyethylene depolymerization and biodegradation.

Omics-based interpretation of synergism in a soil-derived cellulose-degrading microbial community.

Reaching a comprehensive understanding of how nature solves the problem of degrading recalcitrant biomass may eventually allow development of more efficient biorefining processes. Here we interpret genomic and proteomic information generated from a cellulolytic microbial consortium (termed F1RT) enriched from soil. Analyses of reconstructed bacterial draft genomes from all seven uncultured phylotypes in F1RT indicate that its constituent microbes cooperate in both cellulose-degrading and other important metabolic processes. Support for cellulolytic inter-species cooperation came from the discovery of F1RT microbes that encode and express complimentary enzymatic inventories that include both extracellular cellulosomes and secreted free-enzyme systems. Metabolic reconstruction of the seven F1RT phylotypes predicted a wider genomic rationale as to how this particular community functions as well as possible reasons as to why biomass conversion in nature relies on a structured and cooperative microbial community.