Removal Of Microbial Cells Research Articles

Laundry and textile hygiene in healthcare and beyond.

The elimination of microbial contaminations from textile is an important aspect of laundering apart from the removal of stains and dirt from used and worn textiles. Although the framework for institutional laundering is well regulated to ensure hygienic cleanliness via the use of e.g. high temperatures and bleaching agents, there are several open points, especially in domestic laundering. In both cases, energy efficiency of appliances is a main driver for innovation and has resulted in a general decrease in washing temperatures which in turn can impact the antimicrobial efficacy of laundering. Thus, the different factors influencing the input and removal of microbial cells in the laundering process and possible adverse effects of microbial contaminants in the washing machine and on the textiles as well as suitable counteractions are discussed in this article, focusing on the clinical area but also considering the domestic environment, which will gain importance in the future, e.g. by the increase of elderly and ill persons being cared for at home.

Oxide semiconductors for solar to chemical energy conversion: nanotechnology approach

The present work considers the application of oxide semiconductors in the conversion of solar energy into the chemical energy required for water purification (removal of microbial cells and toxic organic compounds from water) and the generation of solar hydrogen fuel by photoelectrochemical water splitting. The first part of this work considers the concept of solar energy conversion by oxide semiconductors and the key performance-related properties, including electronic structure, charge transport, flat band potential and surface properties, which are responsible to the reactivity and photoreactivity of oxides with water. The performance of oxide systems for solar energy conversion is briefly considered in terms of an electronic factor. The progress of research in the formation of systems with high performance is considered in terms of specific aspects of nanotechnology, leading to the formation of systems with high performance. The nanotechnology approach in the development of high-performance photocatalysts is considered in terms of the effect of surface energy associated with the formation of nanostructured system on the formation of surface structures that exhibit outstanding properties. The unresolved problems that should be tackled in better understanding of the effect of nanostructures on properties and performance of oxide semiconductors in solar energy conversion are discussed. This part is summarised by a list of unresolved problems of crucial importance in the formation of systems with enhanced performance. This work also formulates the questions that must be addressed in order to overcome the hurdles in the formation of oxide semiconductors with high performance in water purification and the generation of solar fuel. The research strategy in the development of oxide systems with high performance, including photocatalysts for solar water purification and photoelectrodes for photoelectrochemical water splitting, is considered. The considerations are focused on the systems based on titanium dioxide of different defect disorder as well as its solid solutions and composites.

Use of non-thermal atmospheric plasmas to reduce the viability ofBacillus subtilison spacecraft surfaces

AbstractAtmospheric pressure glow-discharge (APGD) plasmas have been proposed for sterilizing spacecraft surfaces prior to launch. The advantages of APGD plasmas for the sterilization of spacecraft surfaces include low temperatures at treatment sites, rapid inactivation kinetics of exposed microbial cells, physical degradation and removal of microbial cells, physical removal of organic biosignature molecules, and short exposure times for the materials. However, few studies have tested APGD plasmas on spacecraft materials for their effectiveness in both sterilizing surfaces and removal of microbial cells or spores. A helium (He)+oxygen (O2) APGD plasma was used to expose six spacecraft materials (aluminum 6061, polytetrafluoroethylene (PTFE), polycarbonate, Saf-T-Vu, Rastex, and Herculite 20) doped with spores of the common spacecraft contaminant,Bacillus subtilis, for periods of time up to 6 min. Results indicated that greater than six orders of magnitude reductions in viability were observed forB. subtilisspores in as short of time as 40 s exposure to the APGD plasmas. Spacecraft materials were not affected by exposures to the APGD plasmas. However, Saf-T-Vu was the only material in which spores ofB. subtilisadhered more aggressively to plasma-treated coupons when compared to non-plasma treated coupons; all other materials exhibited no significant differences between plasma and non-plasma treated coupons. In addition, spores ofB. subtiliswere physically degraded by exposures to the plasmas beginning at the terminal ends of spores, which appeared to be ruptured after only 30 s. After 300 s, most bacteria were removed from aluminium coupons, and only subtle residues of bacterial secretions or biofilms remained. Results support the conclusion that APGD plasmas can be used as a prelaunch cleaning and sterilization treatment on spacecraft materials provided that the biocidal and cleaning times are shorter than those required to alter surface properties of materials.

Two-Step Cultivation Method for Microbial Disintegration of Tire Rubber Particles

A rubber-degrading strain of Nocardia was cultured on tread rubber particles from a truck tire by a two-step cultivation method. At the first step, the culture medium was either not agitated or stirred at very slow rate of 40 rpm for one or 2 weeks. At the second step, the culture medium was stirred at relatively higher stirring rate of 150 or 300 rpm for seven or six weeks. It was found that the rate of disintegration was greatly increased and the weight losses of the particles with diameters of about 2.3 mm were as high as 40% in the two-step method and only 20–30% in a one-step method in which the stirring rate was kept constant throughout the culture period. With this method, microbial colonization and disintegration were depressed particularly at the corners of the cubic particles and characteristic protuberant structures were observed at the corners after the removal of microbial cells by washing.

CROSSFLOW FILTRATION OF BRINE FROM CUCUMBER FERMENTATION+

Due to environmental concerns, pickle companies are considering ways of reclaiming the brine obtained fromcucumber fermentation. The removal of microbial cells is crucial in use of the brine in finished pickle products. The effectsof transmembrane pressure (41 to 166 kPa), feed flow rate (7.8 to 15.5 L/min), pore size (500,000 NWCO and 0.2 .m), andcell concentration (optical density of 0.171 to 1.170 at 640 nm) on permeate flux during the crossflow filtration of brineobtained from bulk fermentation of cucumber were studied. Results indicate that the microfiltration membranes exhibited alarge flux decline during the first 15 min of operation when challenged with the fermentation brine. The net decline inpermeate flux increased with transmembrane pressure, flow velocity, pore size, and cell concentration. Filtration throughfilter pore size of 0.2 .m or smaller effectively removed the microbial cells present in the brine. Only the transmembranepressure significantly affected the resistance of the cake formed at the filter surface. From the results obtained from the study,it is possible to use microfiltration to filter sediments and microbial cells from brine obtained from cucumber fermentation.

Characteristic behavior of viscosity and viscoelasticity of Aureobasidium pullulans culture fluid

Measurements of dynamic viscoelasticity and steady flow viscosity were made for culture fluids obtained by cultivation of Aureobasidium pullulans IAM 5060 with initial pHs of 6 and 7 and for exopolysaccharide (EPS) solutions obtained by removal of microbial cells. The molecular weight of EPS of the pH 6 culture is about 850,000, and that of the pH 7 culture is much larger. In the present study, the complex viscosity shifted to a considerably larger value than that of the steady flow viscosity. This differs from the Cox-Merz experience law which claims that there is a similarity between the angular frequency dependence of complex viscosity and the shear rate dependence of steady flow viscosity. On the other hand, the dynamic viscosity at small strain amplitude practically corresponded to the steady flow viscosity. The storage modulus of the pH 7 samples decreased markedly with a strain amplitude of more than 0.2, indicating that a dense network structure was formed. The linear region of the plot of viscoelasticity against strain amplitude was wider for the pH 6 culture, reflecting the stability of the network structure in this sample. The viscoelastic level of the EPS solution was a little greater than that of the culture fluid. This suggests that the viscoelasticity of the culture fluid is mainly caused by network structure forming among dissolved polysaccharides.

Microbial degradation of tyre rubber particles

Degradation of rubber particles from tyre treads, having diameters from 0.8 to 2.3 mm, was achieved using Nocardia sp. 835A-Rc, a mutant strain with strong rubber-degrading ability. The entire surface of the particles was uniformly attacked by the organism either without stirring of the culture medium or at a very low stirring rate of 40 rpm. At a higher rate of stirring, however, a small number of large microbial colonies were formed on the rubber surface and separate deep semi-spherical cavities were observed after the removal of microbial cells by washing. The number of microbial colonies decreased with increasing stirring rate but each one of the colonies became larger at the same time. As the result of these two counteracting effects of stirring on microbial activity, the weight loss of the particles increased when the stirring rate was raised from 0 to 40 rpm but decreased when the rate was increased from 40 to 70 or 150 rpm. At the stirring rate of 40 rpm, the weight losses of the particles with mean diameters of about 0.8, 1.1 and 2.3 mm were 57, 50 and 36%, respectively, after 8 weeks. The rate of microbial degradation increased again when the stirring was raised from 150 to 300 rpm.

Removal of microbial cells from water by a filter made of unwoven cloth coated with a pyridinium-type polymer

Removal of microbial cells from water by a filter made of unwoven cloth coated with a pyridinium-type polymer