Genomic insights into antimicrobial potential and optimization of fermentation conditions of pig-derived Bacillus subtilis BS21

Bacillus spp. have been widely used as probiotic supplements in animal feed as alternatives to antibiotics. In the present study, we screened a Bacillus subtilis strain named BS21 from pig feces. Antimicrobial activities, whole genome mining and UHPLC-MS/MS analysis were used to explore its antimicrobial mechanism. Strain BS21 showed Significant growth inhibition against a variety of animal pathogens, including Escherichia coli, Salmonella enterica Pullorum, Salmonella enterica Typhimurium, Citrobacter rodentium, Shigella flexneri and Staphylococcus aureus. Seven gene clusters involved in antimicrobial biosynthesis of secondary metabolites were encoded by strain BS21 genome, including four non-ribosomal peptides (bacillibactin, fengycin, surfactin and zwittermicin A), one ribosomal peptide (subtilosin A), one dipeptide (bacilysin) and one polyketide (bacillaene). Among them, production of surfactin, fengycin, bacillibactin, bacilysin and bacillaene was detected in the supernatant of B. subtilis strain BS21. To develop the potential application of BS21 in animal production, medium components and fermentation parameters optimization was carried out using response surface methodology (RSM). Production of antimicrobial secondary metabolites of strain BS21 was increased by 43.4%, and the best medium formula after optimization was corn flour 2%, soybean meal 1.7% and NaCl 0.5% with optimum culture parameters of initial pH 7.0, temperature 30°C, rotating speed at 220 rpm for 26 h. Our results suggested that strain BS21 has the potential for large-scale production and application as a potential source of probiotics and alternative to antibiotics for animal production

Carboxymethylcellulose reinforced starch films and rapid detection of spoiled beverages

The integrity of the packaging of a liquid foodstuff makes it difficult to detect spoilage. Therefore, it is important to develop a sensitive, fast and real-time material for liquid food detection. CMC, as lignocellulose derivatives and starch are widely used in the food industry. In this study, starch films with pH-responsive properties are successfully prepared from full-component starch and corn amylopectin (CA) by adding CMC. The effects of CMC on the mechanical properties, morphology characteristics, physical and chemical structures, stability and pH responsiveness of the starch films are analyzed. The starch/CMC-1.0 g composite films display good electrical conductivity and reduce the resistance of the composite film by two orders of magnitude. The composite films have pH response ability; in the simulation of orange juice spoilage experiment, the CA/CMC composite film has a more sensitive current response and was more suitable for the application to liquid food quality detection. Additionally, the starch/CMC composite films have potential applications for rapid detection and real-time monitoring of the safety of liquid food

Orbital Origin of Extremely Anisotropic Superconducting Gap in Nematic Phase of FeSe Superconductor

The iron-based superconductors are characterized by multiple-orbital physics where all the five Fe 3$d$ orbitals get involved. The multiple-orbital nature gives rise to various novel phenomena like orbital-selective Mott transition, nematicity and orbital fluctuation that provide a new route for realizing superconductivity. The complexity of multiple-orbital also asks to disentangle the relationship between orbital, spin and nematicity, and to identify dominant orbital ingredients that dictate superconductivity. The bulk FeSe superconductor provides an ideal platform to address these issues because of its simple crystal structure and unique coexistence of superconductivity and nematicity. However, the orbital nature of the low energy electronic excitations and its relation to the superconducting gap remain controversial. Here we report direct observation of highly anisotropic Fermi surface and extremely anisotropic superconducting gap in the nematic state of FeSe superconductor by high resolution laser-based angle-resolved photoemission measurements. We find that the low energy excitations of the entire hole pocket at the Brillouin zone center are dominated by the single $d_{xz}$ orbital. The superconducting gap exhibits an anti-correlation relation with the $d_{xz}$ spectral weight near the Fermi level, i.e., the gap size minimum (maximum) corresponds to the maximum (minimum) of the $d_{xz}$ spectral weight along the Fermi surface. These observations provide new insights in understanding the orbital origin of the extremely anisotropic superconducting gap in FeSe superconductor and the relation between nematicity and superconductivity in the iron-based superconductors.Comment: 19 pages, 4 figure

Coarse Grained Heat-Affected Zone Microstructure and Brittleness of Ti-Nb-B Microalloyed High Toughness and Wear Resistant Steel

The effects of B, Ti-Nb, and Ti-Nb-B microalloying on the microstructure and properties of the coarse grain heat affected zone (CGHAZ) of C-Mn-Si-Mo wear-resistant steel have been investigated by means of thermal simulation, mechanical property test, microstructure analysis, and theoretical formula calculation. The B, Ti-Nb, and Ti-Nb-B microalloyed C-Mn-Si-Mo wear-resistant steels prepared by a controlled rolling + direct quenching + low temperature (CR + DQ + T) process have martensite/bainite (M/B) dual-phase microstructure and fully-refined effective grain size, which make the base metal to have high hardness and impact toughness. At the heat input of 20 kJ/cm, the impact toughness of CGHAZ of three kinds of microalloyed wear-resistant steels decreased in varying degrees. The main reasons for brittleness were coarse grain embrittlement and microstructural embrittlement. Ti-Nb-B microalloying can effectively prevent grain growth in CGHAZ while avoiding the formation of pearlite, small lump ferrite, and large grain carbides at the grain boundaries, thereby reducing the embrittlement of coarse grain and microstructure

Effects of Organizational Leadership on Project Citizenship Behavior and Management Performance in Complex Construction Projects

Organizational leadership is a key factor affecting the management performance of complex construction projects, but seldom have studies attempted to explore the effect mechanisms of organizational leadership on the project management performance, especially the mediating role of project citizenship behavior. The purpose of this study is to fill this gap by investigating the effects of organizational leadership on project citizenship behavior and management performance in complex construction projects. The theoretical model is constructed based on a literature review, and exploratory factor analyses (EFA) are performed on 169 valid questionnaires collected to measure organizational leadership, then partial least squares-structural equation modeling (PLS-SEM) is used to test the hypotheses. The results show that (i) organizational leadership is measured as vision guiding, context interacting, team building, and systems thinking; (ii) vision guiding and context interacting have both direct and indirect effects on the project management performance, and team building can only improve the project management performance by influencing the project citizenship behavior, whereas systems thinking has no significant effect on project citizenship behavior and the project management performance in complex construction projects; (iii) and project citizenship behavior partly mediates the influence of organizational leadership on the project management performance, and the effect of organizational leadership on the project management performance is more realized through the mediating role of project citizenship behavior. The results have a significant theoretical and practical significance for improving the project management performance