Production Of Anti-Fungal Agent By Schizophyllum Commune Against Wood-Degrading Fungi Of Rubberwood

Wood-degrading fungi are serious threat to rubberwood. Chemical preservatives commonly used in rubberwood preserving industry become awareness as it give impact to health and environmental problem. Biological control may be used as an alternative method to solve this problem. In this study, twelve locally isolated wild strains of wood-degrading fungi were screened for their capability to produce antifungal agent. Results showed that methanol extract of Schizophyllum commune biomass provided the highest antifungal activity among the tested fungi with minimum inhibitory concentration (MIC) ranging from 0.1 to 5.0 μg/μl. Chemical compound presence in the biomass extract was analyzed via gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatograph (HPLC). It was found that 4H-pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl- (DDMP), a flavonoid fraction, was presence in the biomass extract. Optimization strategy based on one-factor-at-a-time (OFTA) method and statistical tool were employed to optimize the growth of S. commune in shake flask culture. Based on Plackett-Burman design (PBD), the variables such as yeast extract, glucose and MgSO4·7H2O significantly affected the fungus growth. The optimal values of these process variables were determined using Response Surface Methodology (RSM) coupled with Box-Behnken design (BBD). For the extraction of antifungal agent, the optimum conditions were 70.75% (v/v) methanol, 29 °C, and 145 rpm. All optimization studies were verified and the experimental data fitted well to the selected models with error percentage less than 1%

High pressure effect on structure, electronic structure and thermoelectric properties of MoS2_2

We systematically study the effect of high pressure on the structure, electronic structure and transport properties of 2H-MoS$_2$, based on first-principles density functional calculations and the Boltzmann transport theory. Our calculation shows a vanishing anisotropy in the rate of structural change at around 25 GPa, in agreement with the experimental data. A conversion from van der Waals(vdW) to covalent-like bonding is seen. Concurrently, a transition from semiconductor to metal occurs at 25 GPa from band structure calculation. Our transport calculations also find pressure-enhanced electrical conductivities and significant values of the thermoelectric figure of merit over a wide temperature range. Our study supplies a new route to improve the thermoelectric performance of MoS$_2$ and of other transition metal dichalcogenides by applying hydrostatic pressure.Comment: 6 pages, 6 figures; published in JOURNAL OF APPLIED PHYSICS 113, xxxx (2013

A novel portable oxidation-reduction potential and microbial fuel cell-based sensor to monitor microbial growth

Bioremediation, the most environment-friendly soil remediation method, should receive adequate attention. However, its efficiency has often been criticized, reflecting the dearth of information about microbial activity in the soil. Biosensors can use the signals sent by microorganisms to quantify and analyze microbial activity. Therefore, combining biosensors with bioremediation can enhance the application of bioremediation technology. This thesis focused on designing and fabricating of portable microbial fuel cell (MFC) and oxidation-reduction potential (ORP) based sensor to achieve in situ soil bioremediation application in the future. This is because conventional biosensors cannot reflect the detailed microbial growth characteristics during soil bioremediation. During the experiment, two portable sensors were designed. First, two cylindrical polypropylene bottles were compressed tightly to form a preliminary sensor containing a proton exchange membrane (PEM), an O-ring, and a cathode electrode. After successfully testing the preliminary sensor’s workability, a smaller, easier-to-assemble 3D-printed sensor was designed based on the same concept. The extracellular electrogenic bacterial Bacillus subtilis was used to test both sensors’ workability. MFC and ORP sensors provide voltage and redox potential outputs. By integrating real-time redox potential and voltage outputs, a typical microbial growth (potential parameter) curve can be created. The derivative optical density (OD) value (OD per hour) was found to correspond to the potential parameter. The preliminary sensor could acquire detailed microbial growth characteristics at 6.5 and 18 hours, and the 3D-printed sensor at 10 and 21 hours. The accompanying derivative OD values supported these conclusions. This novel sensor can monitor real-time microbial growth, report detailed growth characteristics in soil, and help select better bioremediation solutions. Future work is required to improve the responsive of the 3D-printed sensor to achieve higher-resolution result

Existence and stability of periodic solution of a Lotka–Volterra predator–prey model with state dependent impulsive effects

AbstractAccording to biological and chemical control strategy for pest, we investigate the dynamic behavior of a Lotka–Volterra predator–prey state-dependent impulsive system by releasing natural enemies and spraying pesticide at different thresholds. By using Poincaré map and the properties of the Lambert W function, we prove that the sufficient conditions for the existence and stability of semi-trivial solution and positive periodic solution. Numerical simulations are carried out to illustrate the feasibility of our main results