Molecular Cloning and Characteristic Features of a Novel Extracellular Tyrosinase from <Emphasis Type="Italic">Aspergillus niger</Emphasis> PA2

Biofertilizers have been widely used in many countries for their benefit to soil biological and physicochemical properties. A new microbial biofertilizer containing Phanerochaete chrysosporium and Bacillus thuringiensis was prepared to decrease nicotine content in tobacco leaves by regulating soil nitrogen supply. Soil NO₃ ^?-N, NH₄ ⁺-N, nitrogen supply-related enzyme activities, and nitrogen accumulation in plant leaves throughout the growing period were investigated to explore the mechanism of nicotine reduction. The experimental results indicated that biofertilizer can reduce the nicotine content in tobacco leaves, with a maximum decrement of 16–18 % in mature upper leaves. In the meantime, the total nitrogen in mature lower and middle leaves increased with the application of biofertilizer, while an opposite result was observed in upper leaves. Protein concentration in leaves had similar fluctuation to that of total nitrogen in response to biofertilizer. NO₃ ^?-N content and nitrate reductase activity in biofertilizer-amended soil increased by 92.3 and 42.2 %, respectively, compared to those in the control, whereas the NH₄ ⁺-N and urease activity decreased by 37.8 and 29.3 %, respectively. Nitrogen uptake was improved in the early growing stage, but this phenomenon was not observed during the late growth period. Nicotine decrease is attributing to the adjustment of biofertilizer in soil nitrogen supply and its uptake in tobacco, which result in changes of nitrogen content as well as its distribution in tobacco leaves. The application of biofertilizer containing P. chrysosporium and B. thuringiensis can reduce the nicotine content and improve tobacco quality, which may provide some useful information for tobacco cultivation.     

Transport Coefficients of Two-temperature Lithium Plasma for Space Propulsion Applications

Lithium has been proposed as an attractive metal propellant for advanced electric propulsion. In our current work, transport coefficients including the viscosity, thermal conductivity, and electrical conductivity of lithium plasma under both the equilibrium and non-equilibrium conditions are calculated based on a two-temperature model. The collision integrals used in calculating the transport coefficients are significantly more accurate than values used in previous theoretical studies, resulting in more reliable values of the transport coefficients. Results are computed for different degrees of thermal non-equilibrium, i.e. the ratio of electron to heavy particle temperatures, from 1 to 15, with the electron temperature ranging from 300 to 60,000 K in a wide pressure range from 0.0001 to 100 atm. We compare our calculated results with existing published results and discrepancies are found and explained.     

Experimental and Theoretical Optimization of Radio Frequency Hollow Cathode Discharge

Plasma Chemistry and Plasma Processing - In this paper, the electron density in radio frequency (RF) hollow cathode discharge (HCD) is investigated in experiments and in simulation based on...     

Thermophilic Dry Methane Fermentation of Distillation Residue Eluted from Ethanol Fermentation of Kitchen Waste and Dynamics of Microbial Communities

Thermophilic dry methane fermentation is advantageous for feedstock with high solid content. Distillation residue with 65.1 % moisture content was eluted from ethanol fermentation of kitchen waste and subjected to thermophilic dry methane fermentation, after adjusting the moisture content to 75 %. The effect of carbon to nitrogen (C/N) ratio on thermophilic dry methane fermentation was investigated. Results showed that thermophilic dry methane fermentation could not be stably performed for >10 weeks at a C/N ratio of 12.6 and a volatile total solid (VTS) loading rate of 1 g/kg sludge/d; however, it was stably performed at a C/N ratio of 19.8 and a VTS loading rate of 3 g/kg sludge/d with 83.4 % energy recovery efficiency. Quantitative PCR analysis revealed that the number of bacteria and archaea decreased by two orders of magnitude at a C/N ratio of 12.6, whereas they were not influenced at a C/N ratio of 19.8. Microbial community analysis revealed that the relative abundance of protein-degrading bacteria increased and that of organic acid-oxidizing bacteria and acetic acid-oxidizing bacteria decreased at a C/N ratio of 12.6. Therefore, there was accumulation of NH₄ ⁺ and acetic acid, which inhibited thermophilic dry methane fermentation.     

Polytetrafluoroethylene Sputtered PES Membranes for Membrane Distillation: Influence of RF Magnetron Sputtering Conditions

Thin films of fluorocarbon were deposited on polyethersulfone membranes via argon plasma sputtering of a poly(tetrafluoroethylene) (PTFE) target in an RF magnetron plasma reactor. The obtained deposited ultrathin coatings had nanoscale roughnesses and high degrees of fluorination. The intensity of fluorine atom in plasma environment during fluorocarbon deposition was investigated. Depending on the deposition conditions comprising working gas pressure, applied RF power, and distance between the target and the substrate, polymeric films with different chemical compositions and/or morphologies were obtained. The morphologies of the films were analyzed by means of SEM, XPS, and AFM. The results suggested that the sputtered film deposited at a higher pressure and longer target–substrate distance and moderate RF power had a surface composition and chemical structure closer to those of the PTFE film. The treated hydrophobic PES membranes with water contact angles as high as 115° were applied for the first time in an air gap membrane distillation setup for removal of benzene as a volatile organic compound from water. The results showed that the plasma-treated membranes have a comparable or superior performance to that of commercial PTFE used in membrane distillation with similar permeate flux and separation factor after 20 h long term performance.     

A Method for Microalgae Proteomics Analysis Based on Modified Filter-Aided Sample Preparation

With the fast development of microalgal biofuel researches, the proteomics studies of microalgae increased quickly. A filter-aided sample preparation (FASP) method is widely used proteomics sample preparation method since 2009. Here, a method of microalgae proteomics analysis based on modified filter-aided sample preparation (mFASP) was described to meet the characteristics of microalgae cells and eliminate the error caused by over-alkylation. Using Chlamydomonas reinhardtii as the model, the prepared sample was tested by standard LC-MS/MS and compared with the previous reports. The results showed mFASP is suitable for most of occasions of microalgae proteomics studies.     

Development of Microtiter Plate Culture Method for Rapid Screening of ε-Poly-L-Lysine-Producing Strains

ε-Poly-l-lysine (ε-PL) produced by Streptomyces albulus possesses a broad spectrum of antimicrobial activity and is widely used as a food preservative. To extensively screen ε-PL-overproducing strain, we developed an integrated high-throughput screening assay using ribosome engineering technology. The production protocol was scaled down to 24- and 48-deep-well microtiter plates (MTPs). The microplate reader assay was used to monitor ε-PL production. A good correlation was observed between the fermentation results obtained in both 24-(48)-deep-well MTPs and conventional Erlenmeyer flasks. Using this protocol, the production of ε-PL in an entire MTP was determined in <5 min without compromising on accuracy. The high-yielding strain selected through this protocol was also tested in Erlenmeyer flasks. The result showed that the ε-PL production of the high-yielding mutants was nearly 45% higher than that of the parent stain. Thus, development of this protocol is expected to accelerate the selection of ε-PL-overproducing strains.     

Metal-Chelate Affinity Precipitation with Thermo-Responsive Polymer for Purification of <Emphasis Type="Italic">ε</Emphasis>-Poly-<Emphasis Type="SmallCaps">l</Emphasis>-Lysine

ε-Poly-l-lysine (ε-PL) is a natural preservative for food processing industry. A thermo-responsive polymer, attached with Cu²⁺ or Ni²⁺, was prepared for metal-chelate affinity precipitation for purification of ε-PL. The low critical solution temperatures (LCSTs) of these polymers were close to the room temperature (31.0–35.0 °C). The optimal adsorption conditions were as follows: pH 4.0, 0 mol/L NaCl, ligand density 75.00 μmol/g, and 120 min. The ligand Cu²⁺ showed a stronger affinity interaction with ε-PL and the highest adsorption amount reached 251.93 mg/g polymer. The elution recovery of ε-PL could be 98.42% with 0.50 mol/L imidazole (pH = 8.0) as the eluent. The method could purify ε-PL from fermentation broth and the final product was proved as electrophoretic pure by SDS-PAGE. Moreover, these affinity polymers could be recycled after the purification of ε-PL and the recoveries were above 95.00%.

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Graphical Abstract Scheme for affinity precipitation of ε-PL

     

Cloning and Characterization of Cold-Adapted α-Amylase from Antarctic <Emphasis Type="Italic">Arthrobacter agilis</Emphasis>

In this study, the gene encoding an α-amylase from a psychrophilic Arthrobacter agilis PAMC 27388 strain was cloned into a pET-28a(+) vector and heterologously expressed in Escherichia coli BL21(DE3). The recombinant α-amylase with a molecular mass of about 80 kDa was purified by using Ni²⁺-NTA affinity chromatography. This recombinant α-amylase exhibited optimal activity at pH 3.0 and 30 °C and was highly stable at varying temperatures (30–60 °C) and within the pH range of 4.0–8.0. Furthermore, α-amylase activity was enhanced in the presence of FeCl₃ (1 mM) and β-mercaptoethanol (5 mM), while CoCl₂ (1 mM), ammonium persulfate (5 mM), SDS (10 %), Triton X-100 (10 %), and urea (1 %) inhibited the enzymatic activity. Importantly, the presence of Ca²⁺ ions and phenylmethylsulfonyl fluoride (PMSF) did not affect enzymatic activity. Thin layer chromatography (TLC) analysis showed that recombinant A. agilis α-amylase hydrolyzed starch, maltotetraose, and maltotriose, producing maltose as the major end product. These results make recombinant A. agilis α-amylase an attractive potential candidate for industrial applications in the textile, paper, detergent, and pharmaceutical industries.     

Developing Novel Antimicrobial and Antiviral Textile Products

In conjunction with an increasing public awareness of infectious diseases, the textile industry and scientists are developing hygienic fabrics by the addition of various antimicrobial and antiviral compounds. In the current study, sodium pentaborate pentahydrate and triclosan are applied to cotton fabrics in order to gain antimicrobial and antiviral properties for the first time. The antimicrobial activity of textiles treated with 3 % sodium pentaborate pentahydrate, 0.03 % triclosan, and 7 % Glucapon has been investigated against a broad range of microorganisms including bacteria, yeast, and fungi. Moreover, modified cotton fabrics were tested against adenovirus type 5 and poliovirus type 1. According to the test results, the modified textile goods attained very good antimicrobial and antiviral properties. Thus, the results of the present study clearly suggest that sodium pentaborate pentahydrate and triclosan solution-treated textiles can be considered in the development of antimicrobial and antiviral textile finishes.