Bacteriocins: Recent Trends and Potential Applications

In the modern era, there is great need for food preservation in both developing and developed countries due to increasing demand for extending shelf life and prevention of spoilage of food material. With the emergence of new pathogens and ability of micro-organisms to undergo changes, exploration of new avenues for the food preservation has gained importance. Moreover, awareness among consumers regarding harmful effects of chemical preservatives has been increased. Globally, altogether there is increasing demand by consumers for chemical-free and minimal processed food products. Potential of bacteriocin and its application in reducing the microbiological spoilages and in the preservation of food is long been recognized. Bacteriocins are normally specific to closely related species without disrupting the growth of other microbial populations. A number of applications of bacteriocin have been reported for humans, live stock, aquaculture etc. This review is focused on recent trends and applications of bacteriocins in different areas in addition to their biopreservative potential.     

Mathematical Model to Estimate the Rate Parameters and Thermal Efficiency for the Reduction of Iron Ore–Coal Composite Pellets in Multi-layer Bed at Rotary Hearth Furnace

Aluminium foams have become popular because of their properties such as high stiffness combined with very low density. The aluminium foams are being used in many applications like automobiles, railways, aerospace, ship building, household applications etc. The development of foam with consistent quality and study of foam structure–property relation is important for both scientific and industrial applications. Metallic foams are commonly produced using hydride and carbonates foaming agents. However carbonate foaming agents are safer to handle than hydrides and produce aluminum foam with a fine, homogenous cell structure, low cost and easily available. The number of pores per inch and relative density of the foam play an important role on their physical and mechanical properties. Hence it is very important to investigate effect of grain size of calcium carbonate foaming agent on pores per inch and relative density. The present work deals with the effect of grain size of the calcium carbonate forming agent on the physical properties of an eutectic Al–Si alloy closed cell foam. The foam was produced with different grain size of calcium carbonate (150, 106, 75, 53 µm) as a foaming agent. The pores per inch and density of the foam produced with different grain size of calcium carbonates as foaming agent are determined. Relative density is in the range of 0.21–0.34, pores per inch is in the range of 11–20 for the produced eutectic Al–Si alloy closed cell foam. It is observed that as grain size of calcium carbonate used for production of aluminium foam increases, the number of pores per inch decreases, relative density decreases and porosity increases.     

Antioxidant-Rich Extract from Dehydrated Seabuckthorn Berries by Supercritical Carbon Dioxide Extraction

Seabuckthorn (Hippophae rhamnoides L.) berry oil having high nutraceutical, cosmeceutical, and therapeutic activity has been extracted from dried seabuckthorn (SBT) whole berry powder using supercritical carbon dioxide (SC-CO₂), a green process for extraction of bioactives. The SC-CO₂ process was optimized using Box?CBehnken design. Three SC-CO₂ parameters namely extracting pressure, extracting temperature, and time of extraction were examined. The optimal SC-CO₂ conditions were determined, and the quadratic response surfaces were drawn from the mathematical models. A maximum recovery of 85.12% tocopherol, 71.73% carotene, and an EC₅₀ of 29.02?mg/ml (from DPPH assay) was obtained after SC-CO₂ extraction at 44?°C, 345?bar, and run time of 80?min. Use of methanol as an entrainer at 30% v/w of SBT berry at optimized conditions further increased the extraction efficiency and the potency. This extract can be used for varied nutraceutical, cosmeceutical, and pharmaceutical applications.     

Investigation of platelet activation and calcium store release by a topical hemostatic xerogel dressing for improved blood clotting

Adequate topical hemostatic dressings are required as first-line approach for reduction of uncontrolled hemorrhage, a leading cause of mortalities. Platelets play a major role during blood clotting to prevent hemorrhage during injuries. Here, we demonstrate the mechanisms activated through protease activating receptor 1 (PAR1), a platelet membrane protein in response to a porous composite xerogel dressing incorporating SiNPs (size 122 ± 10 nm) and calcium (2.5 mM), characterized by scanning electron microscopy–energy dispersive x-ray spectroscopy and Fourier transform infrared spectroscopy. The composite displayed 13.9-fold improved blood clotting index in comparison to commercial dressing. The composite displayed increased platelet aggregation due to development of well-formed pseudopodia as compared to bare xerogel, SFLLRN (a thrombin mimic), adenosine di-phosphate (a platelet activator), and heparin (a thrombin inhibitor). Further, PAR1 gene was significantly upregulated in model A549 epithelial cell line (1.2-fold) and human platelets (1.4-fold). The composite enhanced calcium release and its extrusion in A549 cells. Upregulation of PAR1 on the platelet surface and calcium release are crucial for platelet shape change and aggregation. The data indicate that xerogel composite containing SiNPs and calcium enhanced blood clotting through activation of PAR1. Such dressings can provide a potential hemostatic solution to reduce blood loss, disability, and mortality during surgery and trauma care.     

Structural and physical characteristics of Au2O3-doped sodium antimonate glasses – Part II electrical characteristics

In continuation of our earlier investigations on structural and physical characteristics of Au₂O₃-doped sodium antimonate glass-ceramics (Part-1), in this part we have investigated the influence of gold ions on electrical characteristics of the Na₂O–Sb₂O₃: Au₂O₃ glass-ceramics. The study contains the results of quantitate investigations on dielectric properties, impedance spectra and A.C. conductivity in larger ranges of continuous frequencies (4 Hz-8 MHz) and temperatures (300-630 K). The variations exhibited by dielectric parameters with temperature and also with frequency were discussed in terms of various polarization mechanisms. The observed dielectric relaxation effects were analyzed using pseudo Cole-Cole plot method and the analysis indicated spreading of relaxation times for dipoles. A.c. conductivity and also d.c. conductivity were found to decrease (to three orders of magnitude) with increase in Au₂O₃ concentration upto 0.1 mol%. The decrement is ascribed to the increasing concentration of Sb⁵⁺ ions that were predicted to participate in the glass network forming with SbO₄ units. Even though, both ionic and polaronic contributions are possible for conduction in the studied material, quantitative analysis of these results indicated that the polaronic conduction (due to intervalence transfer between Sb³⁺ ↔ Sb⁵⁺ and Au⁰ ↔ Au³⁺) is prevalent. The results have also suggested that there is a gradual decrement in the ionic component with increase in Au₂O₃ concentration. Variation in σ_ac in the low-temperature region could satisfactorily be explained using quantum mechanical tunneling (QMT) model. Analysis of the results of d.c. conductivity indicated that the small polaron hoping (SPH) model is valid, especially in a high-temperature region while the low temperature part of d.c. conductivity is analyzed based on variable range hopping (VRH) model. Overall, the increase in Au₂O₃ dopant concentration in the studied glass-ceramics caused a decrement in the magnitude of the conductivity or increase in the insulating strength of the material.     

Thermal plasma spheroidization of aluminum oxide and characterization of the spheroidized alumina powder

Spheroidization of aluminum oxide powder was done by thermal plasma processing. The powder was injected into the plasma jet issuing out of a DC plasma torch. Trajectories of the particles in the plasma jet were seen using a high speed camera and then in-flight velocity and temperature of alumina particles were determined using a ‘Spray Watch’ system. Characterization of the spheroidized powder was done by Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The results showed that increase of the plasma torch power leads to increase in the extent of spheroidization and conversion to γ-alumina. Results obtained showed that the process can be extended to synthesize free flowing alumina powder for thermal spray applications.     

EP/AW performance evaluation of some zinc alkyl/dialkyl/alkylaryl‐dithiocarbamates in four‐ball tests

Tribochemistry, the chemistry of interacting surfaces under the influence of a lubricant, helps in the appropriate selection of suitable lubricant additives for specific uses. Modern lubricants are usually formulated from a range of petroleum base oils or synthetic fluids incorporating a variety of chemical additives for performance enhancement. Extreme‐pressure (EP) and anti‐wear (AW) additives are used extensively in lubricants for hypoid gears and metal cutting and forming operations to reduce wear, modify friction, and prevent scuffing of moving metallic parts. The present paper includes the synthesis and the evaluation of the tribological properties of 0.5% (w/v) solutions of some zinc bis‐(alkyl/dialkyl/alkylaryldithiocarbamates) in paraffin oil using 12.7 mm diameter steel bearing ball specimens in four‐ball tests. All the synthesised zinc dithiocarbamate additives in general, and zinc bis‐(morpholinodithio‐carbamate) (A₄) in particular, exhibited good AW, EP, and friction‐reducing properties. Additive A₄ especially gave low values of wear‐scar diameter and coefficient of friction at higher loads and higher values of load wear index and flash temperature parameter during EP tests (ASTM D 2783) and afforded lower values of wear‐scar diameter in a one‐hour wear test (ASTM D 2266–67). The surface topography of the wear‐scar matrix of the used ball specimens was investigated by scanning electron microscopy.