Assessment of Bioaerosol Sampling Techniques for Viable Legionella pneumophila by Ethidium Monoazide Quantitative PCR

Legionella pneumophila causes severe pneumonia and Pontiac fever in humans. Rapid and sensitive bioaerosol monitoring techniques for viable L. pneumophila are unavailable. Coupled with a newly developed viable assay called ethidium monoazide with quantitative PCR (EMA-qPCR), this study applies EMA-qPCR to aerobiology for the first time to evaluate the effects of the method of sampling (all-glass impinger (AGI-30), BioSampler, and MAS-100 sampler) and sampling time (3, 30, 60 min) on the collection of viable L. pneumophila. The effects of the collection fluid (deionized water (DW) and Tween mixture) and the replenishment of DW every 15 min during 60-min sampling were also assessed. Escherichia coli, as a model microorganism in bioaerosol research, was also tested. Using the Tween mixture (DW containing 1% peptone, 0.01% Tween 80, and 0.005% antifoam), the AGI-30 and BioSampler performed significantly better than the MAS-100 sampler for collecting viable L. pneumophila and viable E. coli (P < 0.05). An increase in sampling time adversely affected the quantification of both bacterial species (P < 0.05). The collection with DW yielded greater recovery of viable L. pneumophila than the Tween mixture in both AGI-30 and BioSampler, regardless of sampling time, by a factor of 1.4–6.9 (P < 0.05). The replenishment of DW every 15 min further improved the collection of viable L. pneumophila. This study demonstrates that viable L. pneumophila can be efficiently sampled by the AGI-30 and BioSampler and successfully quantified by EMA-qPCR.     

Microbial Inactivation during Superheated Steam Drying of Fish Meal

Microbial inactivation during superheated steam drying (SSD) of fish meal was investigated in a pilot scale fluidized bed dryer. The exposure times required for 90% reduction in population (D-values) of the surrogate organisms Clostridium sporogenes (spores) and Escherichia coli at 300°C were 0.33 and < 0.10 min, respectively. Corresponding D-values obtained during hot air drying at the same temperature were 54 and 1.12 min. D-value for spores of the thermophile Geobacillus stearothermophilus during SSD was 3.54 min, compared to 228 min in boiling water. The results achieved with surrogate organisms indicate that the target pathogens will be efficiently inactivated by short time SSD.     

Long-term viable bioaerosol sampling using a temperature- and humidity-controlled filtration apparatus,a laboratory investigation using culturable E. coli.

Sampling for culturable (e.g., viable) aerosolized microbes (bioaerosols) is a useful means to provide information for public health monitoring and studies. However, it is challenging to maintain microbe culturability when sampling at high flow rates (>12 L/min) and extended periods of time (≥4 h). We developed a first-generation, viable bioaerosol collection system (VBCS) utilizing temperature (T) and relative humidity (RH)–conditioned filtration at a flow rate of 25 L/min. A two-stage system of tube-in-shell Nafion? exchange units provides cooling to ≤10°C and RH conditioning to 80–95%. Aerosol particles are collected on a polyurethane nanofiber filter providing a physical collection efficiency of >95% for sizes 0.06–10 µm. The T and RH conditions at the collection filter are maintained, despite changes to ambient conditions. The initial testing of the VBCS was done under indoor, laboratory conditions with aerosolized, vegetative E. coli. A scenario of a 30-min challenge of bioaerosol followed by continued sampling of clean air for various times was used to judge culturability maintenance under extended-term sampling. An initial loss of culturability upon collection onto the filter was observed; 23 ± 13% relative to 4-mm all-glass impinger. However once collected, 98% of culturability was maintained for an additional 4.5 h of sampling. An exponential decay in culturability was observed from 8 h to 15 h of sampling. Also, 24-h cold storage of the filters collected was studied. The VBCS is based on the use of dry filter cassettes, needs minimal maintenance, and preserves culturability of vegetative bacteria for >4 h.

© 2017 RTI International and Aerosol Dynamics Inc.     

Design and development of a self-contained personal electrostatic bioaerosol sampler (PEBS) with a wire-to-wire charger

Here, we present a concept of a personal electrostatic bioaerosol sampler (PEBS), which is an open channel collector consisting of a novel wire-to-wire particle charger and a collection section housing a double-sided and removable metal collection plate and two quarter-cylinder ground electrodes. The charger consists of a tungsten wire (25.4 mm long and 0.076 mm in diameter) connected to high voltage and positioned in the center of the charging section (a cylinder 50.8 mm long and 25.4 mm in diameter); a ring of stainless steel wire 0.381 mm in diameter surrounds the hot electrode at its midpoint and is grounded. The newly designed wire-to-wire charger produces lower ozone concentrations compared to traditional wire-to-plate or wire-to-cylinder charger designs. The particles captured on the collection plate are easily eluted using water or other fluids. The sampler was iteratively optimized for optimum charging and collection voltages, and collection electrode geometry. When tested with polystyrene latex particles ranging from 0.026 µm to 3.1 µm in diameter and 10 L/min collection flow rate, the sampler's collection efficiency was approximately 70%–80% at charging and collection voltages of +5.5 kV and ?7 kV, respectively. The PEBS showed this collection efficiency at sampling times ranging from 10 min to 4 h. Preliminary tests with Bacillus atrophaeus bacterial cells and fungal spores of Penicillium chrysogenum showed similar collection efficiency. The use of a unique wire-to-wire charger resulted in ozone production below 10 ppb. Due to low ozone emissions, this sampler will allow maintaining desirable physiological characteristics of the collected bioaerosols, leading to a more accurate sample analysis.

© 2017 American Association for Aerosol Research     

Development and Optimization of the Electrostatic Precipitator with Superhydrophobic Surface (EPSS) Mark II for Collection of Bioaerosols

We recently developed an electrostatic collector for bioaerosols that electrostatically deposits biological particles onto a 3.2 mm electrode covered by a superhydrophobic substance. The deposited biological particles are removed and collected by rolling water droplets (20 or 40 microliter) which results in high concentration rates. The collector has been improved further by integrating it with an electrical charger. Here, we describe the development and optimization of the charger and collection chamber, while maximizing collection efficiency and minimizing particle loss. The resulting sampler is made of static dissipative material (e.g., Delrin), is shaped as a closed half cylinder, and is integrated with a charger. The sampler's round top section contains eight carbon fiber brushes (ion sources to charge particles), while its flat bottom section holds a rectangular collection electrode (254 × 3.2 mm) made of pressed carbon fiber and coated with a superhydrophobic material.

The optimized configuration of the EPSS Mark II had a collection efficiency of up to 84% when sampling airborne Escherichia coli at 10 L/min and for 10 min. The bacteria were accumulated in rolling water droplets as small as 20 microliters, and the sampler achieved sample concentration rates of up to 4.2 × 10⁵/min. When the sampler was operated for a longer time period (60 min), its collection efficiency was 72%. The efficiency decrease was most likely due to a reduced particle removal from the electrode, but the difference was not statistically significant. Since the EPSS Mark II shows satisfactory collection efficiency and high sample concentration rate, it could serve as a basis for developing a field-deployable version of the sampler.

Copyright 2015 American Association for Aerosol Research     

Optimization of Foaming Parameters and Investigating the Effects of Drying Temperature on the Foam-Mat Drying of Shrimp (Penaeus indicus)

In this study, foaming conditions of shrimp (Penaeus indicus) were optimized using response surface methodology (RSM) and the effect of drying temperature on drying behavior was investigated. The experiments were conducted according to face-centered central composite design for three independent variables: xanthan gum concentration (0.1–0.4% w/w), whipping time (2–6 min), and water : shrimp ratio (2:1–6:1 w/w) to minimize the foam density (FD) and the drainage volume (DV) as responses. Statistical analysis of results showed that linear terms of the models were significant (p < 0.01) except the linear term of whipping time in DV. Xanthan gum concentration 0.19% (w/w), water : shrimp ratio 4.5:1 (w/w), and whipping time 5.89 min were found to be the optimum foaming conditions. The effect of different drying temperatures (45, 60, 75, and 90°C) on drying behavior of optimized foam was then evaluated. The drying air temperature had a considerable effect on drying time and drying rate. As the temperature increased from 45 to 90°C, the drying time decreased to 90 min. Drying rate curves showed that foam-mat drying of shrimp principally occurred in the constant rate period. Different mathematical models were tested with the drying behavior of shrimp foam in the dryer. According to the results, the Weibull distribution model is superior to the other models for explaining the drying behavior. Effective moisture diffusivity was calculated and was between 1.114 × 10^?8 and 3.951 × 10^?8 m²/s within the studied temperature range. An Arrhenius relation with an activation energy value of 26.89 kJ/mol expressed the effect of temperature on diffusivity.     

Ozone Disinfection Efficiency for Indicator Microorganisms at Different pH Values and Temperatures

Disinfection efficiency of ozone was determined in various types of water at different pH (6, 7 and 8) values and temperatures (15, 25 and 35 ^°C) for E. coli and Salmonella. Three different applied ozone concentrations (1.5, 1.7, and 2 mg/L) in the gas phase were applied, and samples were taken at different time intervals to determine microbial survival using spread plate count (SPC) and ozone residual. Highest microbial inactivation was observed in distilled water with applied ozone concentration of 2 mg/L in the gas phase. Survival of E. coli was higher at pH 8 and 15 ^°C as compared to lower pH values and temperatures as depicted by the inactivation kinetics of the test microbes used in the study. Salmonella showed 5 and 6 log removal after contact time of 45 and 60 sec, respectively, at 2 mg/L. Disinfection of mixed culture showed relatively more survival of E. coli; as 3 and 4 log removal of E. coli and 4 and 5 log removal of Salmonella was observed after 45 and 60 sec.     

Osmoprotectants enhance methane production from the anaerobic digestion of food wastes containing a high content of salt

BACKGROUND: Treatment and disposal of Korean food waste encounter technical difficulties due to a high‐salt problem. In order to increase methane production from food waste by using osmoprotectants, which are known to overcome osmotic stresses in many plants and other organisms, osmoprotectants including glycine betaine, choline, carnitine and trehalose were added to salt‐containing food wastes for anaerobic digestion. RESULTS: For NaCl‐amended food wastes containing 10 and 35 g L^?1 NaCl, glycine betaine and choline increased methane production by about twofold compared to food waste without any osmoprotectants. For non‐washed food waste containing 11.6 g L^?1 NaCl, glycine betaine increased methane production by about sixfold. Among these osmoprotectants, glycine betaine was the most effective for increasing methane productivity in anaerobic digestion of food waste with salinity. Analysis of glycine betaine in cell extracts using high‐performance liquid chromatography showed that glycine betaine accumulated in the cells of anaerobic sludge. CONCLUSION: Osmoprotectants significantly enhanced methanization of high‐salt food wastes by alleviating the salt‐induced physiological stresses in microorganisms. The application of osmoprotectants provided an effective substitute for other conventional methods to reduce inhibitory effects of high salt, such as dilution and co‐digestion. Copyright © 2008 Society of Chemical Industry     

Investigation of the Efficiencies of Bioaerosol Samplers for Collecting Aerosolized Bacteria Using a Fluorescent Tracer. II: Sampling Efficiency and Half-Life Time

Using uranine as a physical tracer, this study assessed the sampling efficiencies of four bioaerosol samplers (Andersen 6-stage impactor, all glass impinger “AGI-30,” OMNI-3000, and Airport MD8 with gelatin filter) for collecting Gram-positive bacteria (Enterococcus faecalis), Gram-negative bacteria (Escherichia coli and Campylobacter jejuni), and bacteria without cell wall (Mycoplasma synoviae) which were aerosolized in a HEPA isolator. In addition, the half-life times of these bacteria in aerosols were estimated. The uranine concentrations collected by the samplers were used for calculating the physical efficiencies, and the bacteria/uranine ratios were used for calculating the biological efficiencies. The results show the Airport MD8 had the highest physical efficiency. Compared with the Airport MD8, the physical efficiencies of the AGI-30 and the OMNI-3000 were 74% and 49%, respectively. A low physical efficiency of the Andersen impactor (18%) was obtained, but it was mainly caused by the incomplete recovery of uranine when handling the air samples, so could not be ascribed to the sampler efficiency. Both the Andersen impactor and the AGI-30 showed high biological efficiencies for all four bacterial species. The biological efficiencies of the OMNI-3000 for C. jejuni (1%) and of the Airport MD8 for E. coli (38%) and C. jejuni (2%) were significantly lower than 100%, indicating that their sampling stresses inactivated the bacterial culturability. The half-life times at 21–23°C temperature and 80–85% relative humidity were 43.3 min for E. faecalis, 26.7 min for M. synoviae, 21.2 min for E. coli, and 4.0 min for C. jejuni in the air.     

Optimization of Osmo-convective Dehydration Process for the Development of Honey-ginger Candy Using Response Surface Methodology

Osmotic dehydration of ginger with honey is an interesting alternative for the development of confectionary-based functional food with extended shelf life. Response surface methodology (RSM) was used to investigate the effects of process variables on solid gain, water loss, and overall acceptability of honey-ginger candy. The process variables included blanching time (6–10 min), osmotic solution temperature (30–50°C), immersion time (90–150 min), and convective drying temperature (50–70°C). The honey to ginger ratio was 4:1 (w/w) during all the experiments. Ginger cubes were blanched before osmotic dehydration to increase the permeability of the outer cellular layer of tissue. After osmotic concentration of ginger with honey, convective dehydration was done to final moisture content of 3–5% (w.b.) to make it a shelf-stable product. Finally, osmo-convectively dried ginger was coated with sucrose for candy preparation. The optimum osmo-convective process conditions for maximum solid gain, water loss, and overall acceptability of honey-ginger candy were 7.07 min blanching time, 50°C solution temperature, 150 min immersion time, and 60°C convective drying temperature.     

Interesterification of tea seed oil and its application in margarine production

Blends of hydrogenated and nonhydrogenated tea seed oil (Lahijan variety) (30:70, w/w) were chemically interesterified at 60, 90, and 120°C for 30, 60, and 90 min in the presence of 1% (w/w) NaOH. Physicochemical properties of the products were compared with those of the noninteresterified mixture. Statistical comparison of m.p., iodine values (IV), and solid fat contents (SFC) showed that the sample having the highest ranking was interesterified at 120°C for 30 min. The sample was used as a hardstock (40%), with liquid tea seed oil and sunflower oil (ratios of 100:0, 80:20, 60:40, 40:60, 20:80, and 0:100) as, a softstock (60%) for production of table magarine, and the properties of these margarines were compared with those of commercial ones. Samples E and D (ratio of 80:20 and 60:40 liquid tea seed oil/sunflower oil, respectively) had the lowest significant differences with commercial table margarine for physicochemical (m.p., IV, and SFC) and organoleptic characteristics, respectively. Generally, based on m.p. and SFC, margarines E and D were classified as soft margarine. The trans FA content of E, D, and commercial margarines were 1.8, 1.8, and 2.2%, respectively.     

The Viscoelastic Properties of Chinese Fir During Water-Loss Process Under Hydrothermal Conditions

In this article, the viscoelastic properties of water-swollen Chinese fir during a water-loss process under different hydrothermal conditions (30–90°C, 40–80% RH) were investigated. After the 300 min hydrothermal process at 70 or 90°C, the moisture contents (MCs) of the specimens were well below the MC value at the fiber saturation point. During the hydrothermal process, normalized E′ increased at first, and then leveled off at temperatures above 50°C. The wood specimens were softened due to the hydrothermal effect. The glass transition of hemicellulose appeared at 50°C. Lignin transition was observed at 70 and 90°C. Superposition of transitions of lignin and hemicellulose moved to low storage modulus E′ with increasing temperature and RH level.     

A highly efficient method for concentrating DNA from river water by combined coagulation and foam separation

ABSTRACT

Both Escherichia coli and Enterococci were collected in foam within 7 min from 500 mL of bacteria-spiked water by coagulation and foam separation using ferric chloride and milk casein. These bacterial DNA isolated in the 100 µL of extract from the foam more than 87.5% recovery using the DNeasy PowerWater® Kit. To test this method with water from three natural rivers, 0.67–2.70 µg of DNA were concentrated in 100 µL of extract from 1,000 mL of river water. When the DNA extract was subjected to 16S rRNA gene sequencing analysis, information on the bacterial flora could be obtained.     

A novel membrane-assisted fermentation coupling with foam separation for improving the titer of polymyxin E

In this paper, a novel membrane-assisted fermentation coupling with foam separation (M-FCFS) technology was developed to separate polymyxin E from its broth immediately. The effects of starting aeration time, membrane, volumetric airflow rate in foam column, and nitrogen source (i.e. peptone, also known as foam stabilizer) on the production of polymyxin E were studied. Under the optimal conditions, the total titer (TT) of polymyxin E reached 1.29 × 10⁶ IU, resulting in a 50.4% improvement compared with the uncoupling experiment (8.60 × 10⁵ IU). This work combined the advantages of foam separation and membrane filtration, and provided a promising technology for the production of polymyxin E.     

Effect of Agar Plate Volume on Accuracy of Culturable Bioaerosol Impactors

Agar plate volume in bioaerosol impactors affects collection efficiency, but it is often overlooked in practice. This study investigated the effect of agar volume (20, 35, and 50 mL) and, consequently, jet-to-plate distance on accuracy of culturable impactors. Laboratory experiments investigated sensitive Escherichia coli and hardy Bacillus atrophaeus bacteria with a BioStage impactor. Outdoors bacterial and fungal sampling assessed effects of varying agar volume in BioStage, Sampl’air Lite, and SAS Super 180 multinozzle impactors relative to a reference BioStage with 35 mL agar. The results demonstrate that agar plate volume affects not only overall collection efficiency, but also species selection and colony masking. Culturable concentrations of E. coli in laboratory were underestimated by 35% when using 20 versus 35 mL agar volume (p < 0.001). However, data indicate selection of healthier bacteria, as E. coli colonies were significantly larger on 50 versus 20 mL agar plates (p < 0.001). For outdoors, lower agar volume significantly improved accuracy of Sampl’air relative to the reference BioStage for bacterial (p < 0.001) and fungal (p = 0.03) aerosols. Changes for other samplers were not statistically significant, likely due to wide variability in microbial profiles. Outdoors data indicate that culturable concentrations may be positively correlated with increasing dimensionless jet-to-plate distance, especially for bacteria (p = 0.04). This effect may be attributable to sampler jet dissipation with lower nozzle number impactors (i.e., the Sampl’air) being more sensitive. This study demonstrates that bioaerosol impactor agar plate volume should be considered prior to sampling.

Copyright 2013 American Association for Aerosol Research     

Controlled release of Montelukast Sodium from pH-sensitive injectable hydrogels

pH sensitive hydrogels showed excellent drug release properties, with promise for other biomedical applications. Also, the impact of molecular weight (MW) and degree of deacetylation (DDA) of chitosan on the fabricated chitosan/poly (vinyl alcohol) (3:1 mol ratio) hydrogel with selective silane crosslinker amount was evaluated for controlled drug delivery. The FTIR spectroscopy confirmed the incorporated components and the developed interactions among the polymer chains. The hydrogel characteristics were expressed by their responsive behaviour in different environments (water, ionic media and pH). The hydrogel sample (CH1000) having chitosan with higher MW and DDA exhibited more thermal stability and bacterial growth inhibition against E.coli. All hydrogels exhibited maximum swelling at basic and neutral pH and less swelling was observed in acidic media. For drug release analysis performed in simulated gastric fluid, hydrogel showed controlled drug release in 2 h but it was more than 10%, consequently cannot be used for oral purpose. In simulated intestinal fluid, hydrogels exhibited more than 80% release within 90 min. This characteristic phenomenon at neutral pH empowered hydrogel appropriate towards injectable and targeted controlled release of applicable drug. It was concluded that the prepared hydrogel can be administered directly into the venous circulation through syringe and can be used with better results for biomedical applications.     

Role of Water Activity of Liquid in Controlling Evaporation Rate of Low-Viscosity Liquids

Viscosity of liquid is normally the most critical factor when operating an evaporator in an industrial process. This study shows that the dewatering capacity during evaporation for a low-viscosity peptone solution was reduced 40% for water activity (a _w ) = 0.8 and 80% for a _w  = 0.45. Designers of evaporators should be aware of this phenomenon if the aim is to get a high degree of dry matter concentration in the liquid.     

Physical performances and kinetics of evaporation of the CIP 10-M personal sampler's rotating cup containing aqueous or viscous collection fluid

The CIP 10-M personal sampler measures worker exposure to airborne particles by collecting particles in a rotating metal cup containing a few milliliters of a collection fluid. This device is mainly used to sample microorganisms or microbial components to measure bioaerosol concentrations in various occupational environments. Aqueous liquids are generally used, but their rapid evaporation limits the duration of sampling; alternative collection fluids could alleviate this problem. Indeed, the particle-collection efficiency of the rotating cup has not been extensively studied, and the only data available relate to a discontinued model. This study aimed to measure the collection efficiency of the current rotating cup model containing an aqueous (water) or viscous (ViaTrap mineral oil) collection fluid. The kinetics of evaporation confirmed that ViaTrap does not evaporate, making 8-h sampling campaigns in constant volumes feasible. Particles with a wide range of aerodynamic diameters (between around 0.1 and 10 µm) were produced using various test rigs and mono- or polydisperse test aerosols. Both new and older cup models performed similarly, with a collection efficiency of >80% for larger particles (aerodynamic diameters >2.8 µm), progressively decreasing to around 50% for aerodynamic diameters of 2.1 µm; with aerodynamic diameters of <1 µm, the collection efficiency was generally <10%. In physical terms, collection efficiency was unaffected by the type (aqueous or viscous) or volume (between 0 and 3 mL) of collection fluid used. Bias maps indicated that the inhalable fraction may be underestimated in occupational settings, particularly with aerosols mainly composed of particles with aerodynamic diameters of less than around 3 µm.

Copyright © 2016 American Association for Aerosol Research     

EVALUATION OF UV DOSE IN FLOW-THROUGH REACTORS FOR FRESH APPLE JUICE AND CIDER

High absorptivity and turbidity interfere with the UV disinfection of apple cider. Three different configurations of flow-through UV reactors were evaluated to overcome this interference. Two approaches were employed: use of an extremely thin film UV reactor and increasing the turbulence within a UV reactor. Multiple-lamp UV reactors including the thin-film laminar flow “CiderSure” (8 lamps) and turbulent flow “Aquionics” (12 lamps) and annular single-lamp “UltraDynamics” reactor were studied. UV disinfection performance in laminar and turbulent flow reactors was compared by evaluation of UV dose delivery. UV fluence rate (irradiance) distribution was calculated using the multiple point source summation method. E. coli K12 was used as a target bacterium in a bioassay, and the log reduction per one pass was determined for each UV reactor. Finally, the UV decimal reduction dose (D₁₀) was calculated by dividing the average UV fluence by log bacterial reduction per pass. Variations of the UV decimal dose were observed with various designs of UV systems. The least inactivation of E. coli K12 but the highest UV decimal reduction dose, ranging from 90 to 150 mJ/cm², was observed in the Aquionics UV reactor in apple cider with apparent absorption coefficient (a) of 5.7 mm^?1. The lower value of UV decimal reduction dose of 7.3–7.8 mJ/cm² was required for inactivation of E. coli K12 in malate buffer and apple juice in the annular single-lamp UltraDynamics reactor. However, the decimal reduction dose for E. coli K12 in apple cider was significantly higher, about 20.4 mJ/cm². Similar UV decimal reduction doses from 25.1 to 18.8 mJ/cm² for inactivation of E. coli K12 were observed in the thin-film ‘CiderSure’ UV reactor in apple cider with identical absorption coefficient. Mathematical modeling of UV irradiance can improve the evaluation of UV dose delivery and distribution within the reactors.     

Pressurized Liquid and Superheated Water Extraction of Active Constituents from Zingiber cassumunar Roxb. Rhizome

Active compounds, terpinene-4-ol and (E)-1-(3,4-dimethoxyphenyl) butadiene (DMPBD), displaying anti-inflammatory activity, were successfully extracted from the rhizome of Zingiber cassumunar Roxb. by pressurized liquid extraction (PLE) using methanol or ethanol and by superheated water extraction (SWE). Optimum conditions of both techniques were 1 mL/min flow rate and 5 min static time. The extraction temperature and dynamic time of the PLE and the SWE were 100°C 5 min and 140°C 20 min, respectively. Compared with water distillation, solvent sonication, and Soxhlet extraction, the PLE produced the highest amount of DMPBD and terpinene-4-ol, whereas the SWE and water distillation provided similar results.