Statistical optimization of culture medium for improved production of antimicrobial compound by Streptomyces rimosus AG-P1441

Food Science and Biotechnology - The nutritional requirements for antimicrobial activity of Streptomyces rimosus AG-P1441 were optimized using statistically-based experimental designs at a flask...     

The Role of the Gut Microbiota in the Gut–Brain Axis in Obesity: Mechanisms and Future Implications

Interaction between the gut and the brain is essential for energy homeostasis. In obesity, this homeostasis is disrupted, leading to a positive energy balance and weight gain. Obesity is a global epidemic that affects individual health and strains the socioeconomic system. Microbial dysbiosis has long been reported in obesity and obesity-related disorders. More recent literature has focused on the interaction of the gut microbiota and its metabolites on human brain and behavior. Developing strategies that target the gut microbiota could be a future approach for the treatment of obesity. Here, we review the microbiota–gut–brain axis and possible therapeutic options.     

One-Level Simplification Method for All-Optical Combinational Logic Circuits

We propose a novel one-level simplification method for all-optical combinational logic circuits. With the proposed method, an all-optical gray code to binary coded decimal converter is successfully developed for the first time by using conventional semiconductor optical amplifiers as building elements. In comparison to the construction algorithm based on the conventional two-level simplification method, a significant improvement is observed in the Q-factor.     

Viewing Zones in PLS Based Multiview 3-D Imaging Systems

In 3D imaging systems, with a point light source (PLC) array as a backlight illumination and viewing zone forming, the finite size of the light-emitting surface of each PLC in the array and mismatch between the array period and pixel cell pitch limits the region of individual view image to a small portion of the viewing zone cross section (VZCS). The portion becomes smaller as the size approaches that of a pixel for an individual view image in the pixel cell, and/or the fractional size of the pixel becomes smaller. As a consequence, the VZCS becomes filled with viewing regions for mixed images of two adjacent view images. Hence, the effective number of different images which can be viewed at VZCS could be increased around two times that of the total different view images displayed on the display panel.     

Antioxidant effects of solvent extracts from the dried jujube (Zizyphus jujube) sarcocarp,seed, and leaf via sonication

Antioxidant effects of extracts from sarcocarp, seed, and leaf of dried jujube (Zizyphus jujube) were investigated. The highest amount of flavonoids and polyphenol was found in 80% methanol leaf extract at value of 43.04±0.34 and 324.75±6.01 mg/g, respectively. For 2,2′-azino-bis-3-ethylbenzo-thiazoline-6-sulfonic acid (ABTS) radical scavenging activity analysis at a concentration of 1,000 μg/mL, 70% ethanol seed extract (94.76±0.23%), and 80% methanol leaf extract (95.46±0.14%) were observed to have higher activity than those of controls, such as butylated hydroxyl anisole (BHA) (89.60±0.00%), butylated hydroxyl toluene (BHT) (84.07±0.50%), vitamin C (89.27±0.12%), and vitamin E (88.53±0.12%). All solvent extracts from leaf showed higher ABTS radical scavenging activity (over 98%) than those of controls with their activity values around 94% (500 g/mL). All extracts from sarcocarp and seed showed superoxide dismutase (SOD)-like activity of 24.46–34.84% on the concentrations (100–1,000 g/mL), and 80% methanol leaf extract showed the highest activity (43.66±0.37%) among samples. These results indicate that sarcocarp, seed of dried jujube are all excellent antioxidants, and especially leaf showed higher antioxidant effect than those of vitamin C and E.     

Dehydration characteristics of Maesaengi (Capsosiphon fulvescens) in hot-air drying

Maesaengi (Capsosiphon fulvescens) was dehydrated in a single layer at drying air temperatures ranging from 50–80°C in a laboratory scale convective dryer with an air velocity of 0.26 m/s. The effect of drying air temperature on the drying kinetic characteristics was determined. Maesaengi was dried to equilibrium moisture content within 200–600 min under these drying conditions. Drying rate curves of maesaengi showed an initial short period of a constant drying rate, followed by a falling drying rate period. The moisture decrease in the sample during dehydration was well described by the zero-order kinetic model. An Arrhenius-type equation was used to test the effect of temperature on drying rate according to an activation energy value of 29.36 kJ/mol.     

Antibacterial electrospun chitosan/poly(vinyl alcohol) nanofibers containing silver nitrate and titanium dioxide

Chitosan/poly(vinyl alcohol) (PVA) nanofibers with antibacterial activity were prepared by the electrospinning of a chitosan/PVA solution with a small amount of silver nitrate (AgNO₃) and titanium dioxide (TiO₂). Nanofibers with diameters of 270–360 nm were obtained. The yield of low‐viscosity chitosan (LCS)/PVA nanofibers was higher than that of high‐viscosity chitosan (HCS)/PVA, and the water content of the HCS/PVA nanofibers and the LCS/PVA nanofibers were 430 and 390%, respectively. The nanofibers developed in this study exhibited antibacterial activities of 99 and 98% against Staphylococcus aureus and Escherichia coli, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Prediction of bitumen content in oil sand based on FT-IR measurement

FT-IR spectra of bitumen are utilized to propose simple prediction method of bitumen content in oil sand. Analysis and fractionation of Athabasca oil sand were carried out by standard method. A fraction of bitumen dissolved in tetrahydrofuran (THF) was 9.1 wt% and insoluble fraction was found as concomitantly clean clay (sand). The asphaltene fraction of oil sand was 1.42 wt%, which has higher sulfur content and lower H/C molar ratio than that of maltene. The clean clay and bitumen were used to prepare clay/bitumen composites. FT-IR spectra of different clay/bitumen composite were measured and compared. From analysis of the absorbance data, the empirical equation to predict bitumen content in oil sand was acquired using linear least square fitting. Using this equation, bitumen content of Athabasca oil sand was predicted to have a value of 10.5 wt% which is similar to 9.1 wt% of bitumen content extracted by THF solvent from oil sand.     

Inhibitory effect of oxalic acid on bacterial spoilage of raw chilled chicken

Oxalic acid was evaluated as a treatment for reducing populations of naturally occurring microorganisms on raw chicken. Raw chicken breasts were dipped in solutions of oxalic acid (0, 0.5, 1.0, 1.5, and 2.0%, wt/vol) for 10, 20, and 30 min, individually packed in oxygen-permeable polyethylene bags, and stored at 4 degrees C. Total plate counts of aerobic bacteria and populations of Pseudomonas spp. and Enterobacteriaceae on breasts were determined before treatment and after storage for 1, 3, 7, 10, and 14 days. The pH and Hunter L, a, and b values of the breast surface were measured. Total plate counts were ca. 1.5 and 4.0 log CFU/g higher on untreated chicken breasts after storage for 7 and 14 days, respectively, than on breasts treated with 0.5% oxalic acid, regardless of dip time. Differences in counts on chicken breasts treated with water and 1.0 to 2.0% of oxalic acid were greater. Populations of Pseudomonas spp. on chicken breasts treated with 0.5 to 2.0% oxalic acid and stored at 4 degrees C for 1 day were less than 2 log CFU/g (detection limit), compared with 5.14 log CFU/g on untreated breasts. Pseudomonas grew on chicken breasts treated with 0.5% oxalic acid to reach counts not exceeding 3.88 log CFU/g after storage for 14 days. Counts on untreated chicken exceeded 8.83 log CFU/g at 14 days. Treatment with oxalic acid caused similar reductions in Enterobacteriaceae counts. Kocuria rhizophila was the predominant bacterium isolated from treated chicken. Other common bacteria included Escherichia coli and Empedobacter brevis. Treatment with oxalic acid caused a slight darkening in color (decreased Hunter L value), retention of redness (increased Hunter a value), and increase in yellowness (increased Hunter b value). Oxalic acid has potential for use as a sanitizer to reduce populations of spoilage microorganisms naturally occurring on raw chicken, thereby extending chicken shelf life.     

An experimental study on heat transfer and pressure drop characteristics of carbon dioxide during gas cooling process in a horizontal tube

The heat transfer coefficient and pressure drop during gas cooling process of CO₂ (R744) in a horizontal tube were investigated experimentally. The experiments are conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater and a gas cooler (test section). The water loop consists of a variable speed pump, an isothermal tank, and a flow meter. The refrigerant, circulated by the variable-speed pump, condenses in the inner tube while water flows in the annulus. The gas cooler of tube diameter is 6000 mm in length, and it is divided into 12 subsections.The pressure drop of CO₂ in the gas cooler shows a relatively good agreement with those predicted by Blasius's correlation. The local heat transfer coefficient of CO₂ agrees well with the correlation by Bringer–Smith. However, at the region near Pseudo-critical temperature, the experiments indicate higher values than the Bringer–Smith correlation. Based on the experimental data presented in this paper, a new correlation to predict the heat transfer coefficient of supercritical CO₂ during in-tube cooling has been developed. The majority of the experimental values are within 18% of the values predicted by the new correlation.