Microbial destruction of cyanide and thiocyanate

The role played by a bacterial community composed of Pseudomonas putida, strain 21, Pseudomonas stutzeri, strain 18, and Pseudomonas sp., strain 5, and by physical and chemical factors in the degradation of CN- and SCN- was studied. It was shown that the degradation of CN- is determined both by the action of bacteria and by abiotic physical and chemical factors (pH, O2, temperature, the medium agitation rate, etc.). The contribution of chemical degradation was found to increase drastically at pH below 9.0; when air was blown through the medium (irrespective of the pH value); under active agitation of the medium; and when the medium surface interfacing air was increased. Even at elevated pH values (9.0-9.2), suboptimal for bacterial growth, the microbial degradation could account for at most 20-25 mg/l of CN-, regardless of its initial concentration. When CN- and SCN- were concurrently present in the medium, the former compound was the first to be degraded by microorganisms. The rate of bacterial degradation of SCN- under continuous cultivation in a chain of reactors was found to depend on its concentration, the medium flow rate, agitation rate, and the pattern of carbon source supply and could exceed 1 g/(1 day). CN- and SCN- are utilized by bacteria solely as nitrogen sources. The mechanism of CN- and SCN- degradation by the microbial community is discussed.     

Microbial degradation of cyanide and thiocyanate

The role played by a bacterial community composed ofPseudomonas putida, strain 21;Pseudomonas stutzeri, strain 18; andPseudomonas sp., strain 5, and by physical and chemical factors in the degradation of CN⁻ and SCN⁻ was studied. It was shown that the degradation of CN⁻ is determined both by the action of bacteria and by abiotic physical and chemical factors (pH, O₂, temperature, the medium agitation rate, etc.). The contribution of chemical degradation was found to increase drastically at pH below 9.0; when air was blown through the medium (irrespective of the pH value); under active agitation of the medium; and when the medium surface interfacing air was increased. Even at elevated pH values (9.0-9.2), suboptimal for bacterial growth, the microbial degradation could account for at most 20–25 mg/1 of CN⁻, regardless of its initial concentration. When CN⁻ and SCN⁻ were concurrently present in the medium, the former compound was the first to be degraded by microorganisms. The rate of bacterial degradation of SCN⁻ under continuous cultivation in a chain of reactors was found to depend on its concentration, the medium flow rate, agitation rate, and the pattern of carbon source supply and could exceed 1 g/(l day). CN⁻ and SCN⁻ are utilized by bacteria solely as nitrogen sources. The mechanism of CN⁻ and SCN⁻ degradation by the microbial community is discussed. Deceased.     

Growth models of the continuous bacterial leaching of iron pyrite by Thiobacillus ferrooxidans

The leaching of iron pyrite by Thiobacillus ferrooxidans was studied in a continuous stirred tank reactor at a variety of dilution rates (0.012-0.22 h(-1)), pyrite surface areas (18-194 m(2)/L), and inlet soluble substrate (Fe(2+)) concentrations (0-3000 ppm). The bacterial leaching rate was found to increase with increasing pyrite surface area, dilution rate, and inlet Fe(2+) concentration. The concentration of bacteria in solution was related to the concentration of bacteria attached to the pyrite surface by a Langmuir-type adsorption-desorption relation. Fitting the experimental data to this relation yielded a value for the area occupied per bacterium of 86 mum(2). This result is consistent with the concept of preferential bacterial attachment of certain sites on the solid. A bacterial growth model was developed that included both bacterial growth in solution and growth of bacteria attached to the pyrite surface. The specific growth rate of the attached bacteria was calculated from this model and was found to increase with increasing solid dilution rate and to decrease with increasing pyrite surface area and soluble substance concentration. An explanation of these results based on an active-inactive site mechanisms was also developed.     

Hydrodynamic effects on BHK cells grown as suspended natural aggregates

Baby hamster kidney (BHK) cell aggregates grown in stirred vessels with different working volumes and impeller sizes were characterized. Using batch cultures, the range of agitation rates studied (25-100 rpm) led to aggregates with maximum sizes of 150 mum. Necrotic centers were not observed and cell specific productivity was independent of aggregate size. High cell viability was found for both single and adherent cells without an increase in cell death when agitation rate was increased. The increase in agitation rate affected aggregates by reducing their size and increasing their concentration and cell concentration in aggregates, while increasing the fraction of free cells in suspension. The experimental relationship between aggregate size and power dissipation rate per unit of mass was close to -1/4, suggesting a correlation with a critical turbulence microscale; this was independent of vessel scale and impeller geometry over the range investigated. Viscous stresses in the viscous dissipation subrange (below Kolmogoroff eddies) appear to be responsible for aggregate breakage. Under intense agitation BHK cells grown in the absence of microcarriers existed as aggregates without cell damage, whereas cells grown on the surface of microcarriers were largely reduced. This is a clear advantage for scaleup purposes if aggregates are used as a natural immobilization system in stirred vessels. (c) 1995 John Wiley & Sons, Inc.     

Quantification of the relationship between bacterial kinetics and host response for monkeys exposed to aerosolized Francisella tularensis

Francisella tularensis can be disseminated via aerosols, and once inhaled, only a few microorganisms may result in tularemia pneumonia. Effective responses to this threat depend on a thorough understanding of the disease development and pathogenesis. In this study, a class of time-dose-response models was expanded to describe quantitatively the relationship between the temporal probability distribution of the host response and the in vivo bacterial kinetics. An extensive literature search was conducted to locate both the dose-dependent survival data and the in vivo bacterial count data of monkeys exposed to aerosolized F. tularensis. One study reporting responses of monkeys to four different sizes of aerosol particles (2.1, 7.5, 12.5, and 24.0 μm) of the SCHU S4 strain and three studies involving five in vivo growth curves of various strains (SCHU S4, 425, and live vaccine strains) initially delivered to hosts in aerosol form (1 to 5 μm) were found. The candidate models exhibited statistically acceptable fits to the time- and dose-dependent host response and provided estimates for the bacterial growth distribution. The variation pattern of such estimates with aerosol size was found to be consistent with the reported pathophysiological and clinical observations. The predicted growth curve for 2.1-μm aerosolized bacteria was highly consistent with the available bacterial count data. This is the first instance in which the relationship between the in vivo growth of F. tularensis and the host response can be quantified by mechanistic mathematical models.     

The role of aeration and agitation in the production of glucose oxidase in submerged culture

The influence of agitation and aeration on growth and on production of glucose oxidase of Asp. niger has been studied. It was found that both rate of growth and glucose oxidase production was higher at an agitation speed of 700 rpm than at 460 rpm. Further increase in speed of agitation resulted in neither a higher rate of growth nor a higher glucose oxidase activity. Total glucose oxidase activity was highest in a medium containing 5% sugar (at an agitation speed of 700 rpm) and did not get higher when the sugar concentration of the medium was increased to 7%. When pure oxygen was bubbled through the culture the rate of growth of the culture (in the linear phase) was 95 mg. mycelial dry wt./100 ml./hr., and only 61 mg. when air was applied. The glucose oxidase activity of oxygenated culture was double the activity of aerated culture. Viscosity of the homogenized culture became higher with higher concentration of mycelia. The viscosity of oxygenated culture was found to be lower than that of aerated culture.     

Preparation and in vitro analysis of microencapsulated genetically engineered E. coli DH5 cells for urea and ammonia removal

This article describes a novel method of urea and ammonia removal using microencapsulated, genetically engineered Escherichia coli DH5 cells. Optimization of bacterial cell encapsulation was carried out. The optimal method consists of alginate 2.00% (w/v) at a flow rate of 0.0724 mL/min and a coaxial air flow rate of 2.00 L/min. This produces spherical, alginate-poly-L-lysine-alginate (APA) microcapsules of an average 500 +/- 45 mum diameter. Increasing the concentration of alginate from 1.00% to 1.75% improves the quality of the microcapsules, while cell viability remains unaffected. The APA microcapsules are mechanically stable up to 210-rpm agitation with no bacterial cell leakage. The in vitro performance of urea and ammonia removal by encapsulated bacteria is assessed. One hundred milligrams of bacterial cells in APA microcapsules, in their log phase state of growth, can lower 87.89 +/- 2.25% of the plasma urea within 20 min and 99.99% in 30 min. The same amount of encapsulated bacteria can also lower ammonia from 975.14 +/- 70.15 muM/L to 81.151 +/- 7.37 muM/L in 30 min. There are no significant differences in depletion profiles by free and encapsulated bacteria for urea and ammonia removal. This novel approach using microencapsulated, genetically engineered E. coli cells is significantly more efficient than presently available methods of urea and ammonia removal. For instance, it is 30 times more efficient than the standard urease-ammonium adsorbent system. (c) 1995 John Wiley & Sons, Inc.     

The impact of fluid mechanical stress on <Emphasis Type="Italic">Corynebacterium glutamicum</Emphasis> during continuous cultivation in an agitated bioreactor

The effect of mechanical stresses generated by an extreme agitation intensity or a high aeration rate on growth parameters and cell physiology were studied during continuous cultivation of the Gram-positive bacterium Corynebacterium glutamicum. It is concluded that variations in agitation, aeration rate, or dO₂ concentrations down to about 1% of saturation do not damage the bacterial cells or cause a significant change in physiological response, as measured by flow cytometry, even though the cell size was slightly reduced.     

Cell retention culture with an internal filter module: continuous ethanol fermentation

A new internal filter feedback system with a stainless steel filter was introduced and its application for continuous ethanol fermentation was investigated. The filter performance was highly influenced by agitation speed and yeast concentration. Retention coefficient with a filter of 2 mum pore size was found more than 97.5%, and the filter was suitable for yeast separation. Maximum yeast concentration was 157 g/L and the best operable cell concentration was between 90 and 150 g/L. Which was similar to that obtained in the external membrane cell recycle culture. The cell concentration in the fermentor was maintained by manipulation of dilution rate and bleed ratio with the growth rate. The internal filter feedback system was successfully operated for more than 10 days. This study shows that the internal filter feedback system with a stainless steel filter can be used high-density cell culture and ethanol fermentation. Furthermore, it can be scaled up more easily than the external cell recycle system. (c) 1993 John Wiley & Sons, Inc.     

Human occupancy as a source of indoor airborne bacteria

Exposure to specific airborne bacteria indoors is linked to infectious and noninfectious adverse health outcomes. However, the sources and origins of bacteria suspended in indoor air are not well understood. This study presents evidence for elevated concentrations of indoor airborne bacteria due to human occupancy, and investigates the sources of these bacteria. Samples were collected in a university classroom while occupied and when vacant. The total particle mass concentration, bacterial genome concentration, and bacterial phylogenetic populations were characterized in indoor, outdoor, and ventilation duct supply air, as well as in the dust of ventilation system filters and in floor dust. Occupancy increased the total aerosol mass and bacterial genome concentration in indoor air PM(10) and PM(2.5) size fractions, with an increase of nearly two orders of magnitude in airborne bacterial genome concentration in PM(10). On a per mass basis, floor dust was enriched in bacterial genomes compared to airborne particles. Quantitative comparisons between bacterial populations in indoor air and potential sources suggest that resuspended floor dust is an important contributor to bacterial aerosol populations during occupancy. Experiments that controlled for resuspension from the floor implies that direct human shedding may also significantly impact the concentration of indoor airborne particles. The high content of bacteria specific to the skin, nostrils, and hair of humans found in indoor air and in floor dust indicates that floors are an important reservoir of human-associated bacteria, and that the direct particle shedding of desquamated skin cells and their subsequent resuspension strongly influenced the airborne bacteria population structure in this human-occupied environment. Inhalation exposure to microbes shed by other current or previous human occupants may occur in communal indoor environments.     

Modified Spinning Top Homogeneous Spray Apparatus for Use in Experimental Respiratory Disease Studies

The May spinning top generator was adapted to a modified Henderson tube for producing large aerosol particles (>4 mum) to obtain almost exclusive upper respiratory tract deposition of infectious aerosols in exposed mice. The system was installed in a biological safety cabinet to permit experimentation with pathogens. A novel mechanism utilizing parts from a machinists micrometer and the mechanical stage from a light microscope was developed for the spinning top generator as a means for precisely positioning the liquid feed needle. Aerosol light-scatter properties were continuously analyzed to provide relative measures of particle size distribution and aerosol concentration. When mice were exposed to influenza virus aerosols in which none of the virus was contained in particles with aerodynamic diameters <4 mum, essentially all of the virus was deposited in the upper respiratory tract tissues.     

Microencapsulation of mammalian cells in a water-insoluble polyacrylate by coextrustion and interfacial precipitation

A process for the microencapsulation of mammalian cells in a commercially available water-insoluble polyacrylate (EUDRAGIT RL) is described, and the effects of process parameters are outlined The polymer dissolved in diethyl phthalate was pumped along the annulus formed from two concentric needles, while the cell suspension was pumped inside the inner needle Droplets of polymer solution containing cells were blown off the end of the needles by a coaxial air stream. The droplets fell into a corn oil-mineral oil curing bath, in which the solvent was removed from the nascent capsule causing the polymer to precipitate around the cell suspension core. Capsules were washed free of oils and solvent in a fractionated plasma that allowed for quantitative transfer of capsules from the oil phase to an aqueous medium. By appropriate adjustment of the coaxial air flow rate, capsule size could be varied from 250-1000 mum, although the most convenient size was found to be 400-700 mum. Adding Ficoll 400 to the cell suspension to match the density of the suspension to the polymer solution resulted in capsules with a well-centered core but did not affect capsule strength. It appeared that increasing the polymer solution concentration or the polymer to the cell flow rate ratio resulted in an increased capsule strength, although differences in capsule size made unequivocal conclusions difficult. These capsules are of potential use as an artificial pancreas for the treatment of diabetes (with pancreatic islets) or for large-scale tissue culture and the production of bioactive products (e.g., with fibroblasts).     

Biocalorimetric studies of the metabolic activity of Pseudomonas aeruginosa aerobically grown in a glucose-limited complex growth medium

Biocalorimetric experiments were performed to investigate the aerobic growth of Pseudomonas aeruginosa, isolated from tannery saline wastewater. Growth factors (pH, Inoculum size, carbon source, temperature, aeration rate, and agitation rate) were optimized in shaker and calorimeter based on the growth of P. aeruginosa and heat generation rates. A limiting value of 0.2% glucose concentration was found to be optimum for the growth of P. aeruginosa in a complex growth medium, and the heat flux (q(r)) profiles resulting from the metabolic activity of P. aeruginosa further confirmed this observation. The bacterial growth profile was found to correlate well with the metabolic heat generated. Heat-yield values were calculated for both glucose consumption and the growth of P. aeruginosa from the calorimetric results. Metabolic shifts in substrate uptake from glucose to peptone present in growth medium was observed by the variations in heat-flux profile. The calorimetric data presented in this study should be useful in understanding the behavior of the isolated bacterial strain in degrading complex and mixed substrates commonly observed in tannery saline waste stream, and further to extend the results for scale-up studies.     

Homogeneous Bacterial Aerosols Produced with a Spinning-Disc Generator

Aerosols composed of viable particles of a uniform size were produced with a commercial spinning-disc generator from aqueous suspensions of Bacillus subtilis var. niger spores containing various amounts of an inert material, dextran, to regulate aerosol particle size. Aerosols composed of single naked spores having an equivalent spherical diameter of 0.87 mum were produced from spore suspensions without dextran, whereas aerosols produced from suspensions containing 0.001, 0.01, 0.1, and 1% dextran had median diameters of 0.90, 1.04, 1.80, and 3.62 mum, respectively. Such aerosols, both homogeneous and viable, would be useful for calibrating air sampling devices, evaluating air filter systems, or for employment wherever aerosol behavior may be size-dependent.     

Protease production by fermentation of fish solubles from salmon canning processes

Production of protease by fermentation, using Sorangium 495, of a substrate based on condensed fish solubles is demonstrated. The effects of carbohydrate addition, pH, fish solubles concentration, scale-up, agitation, and air flow rate on protease yields are described. While the fish solubles medium alone could give rise to measurable yields of protease, these were, at worst, doubled when 1% glucose was added to the medium. pH 7 was optimal for protease yield. Although the concentration of fish solubles in the basic medium showed no significant effect on cell yield, maximum protease yield was observed at a protein concentration equivalent to 3.85 mg/mL of bovine serum albumin. Protease production rates decreased as medium protein fermentor showed no significant effect on maximum protease yields. The effects of agitator speed and air flow rate on protease yield suggested that the rate of O2 transfer from air to medium could limit the rate of protease production. It was also noted that protease production is not growth associated.     

The role of aeration and agitation in the production of glucose oxidase in submerged culture. II

The main purpose of the work reported here was to establish the effectiveness of aeration and agitation, and to determine the best conditions of aeration for the growth and production of glucose oxidase of Aspergillus niger, on a semi-industrial scale. Concentration of dissolved O₂, O₂ consumption and CO₂ production were measured. It was found that the rate of growth and the activity of glucose oxidase per gram mycelium increased with the increase of speed of agitation. The concentration of dissolved oxygen of the fermentation broth, as well as the rate of respiration (O₂ consumption and CO₂ production) increased in direct proportion to the increase of speed of agitation, while assimilation of sugars was accelerated. The values of the respiratory ratio showed a fluctuation according to the presence or absence of sugar in the medium.     

Characterization of airborne bacteria at an underground subway station

The reliable detection of airborne biological threat agents depends on several factors, including the performance criteria of the detector and its operational environment. One step in improving the detector's performance is to increase our knowledge of the biological aerosol background in potential operational environments. Subway stations are enclosed public environments, which may be regarded as potential targets for incidents involving biological threat agents. In this study, the airborne bacterial community at a subway station in Norway was characterized (concentration level, diversity, and virulence- and survival-associated properties). In addition, a SASS 3100 high-volume air sampler and a matrix-assisted laser desorption ionization-time of flight mass spectrometry-based isolate screening procedure was used for these studies. The daytime level of airborne bacteria at the station was higher than the nighttime and outdoor levels, and the relative bacterial spore number was higher in outdoor air than at the station. The bacterial content, particle concentration, and size distribution were stable within each environment throughout the study (May to September 2010). The majority of the airborne bacteria belonged to the genera Bacillus, Micrococcus, and Staphylococcus, but a total of 37 different genera were identified in the air. These results suggest that anthropogenic sources are major contributors to airborne bacteria at subway stations and that such airborne communities could harbor virulence- and survival-associated properties of potential relevance for biological detection and surveillance, as well as for public health. Our findings also contribute to the development of realistic testing and evaluation schemes for biological detection/surveillance systems by providing information that can be used to mimic real-life operational airborne environments in controlled aerosol test chambers.     

Studies on the production of bacterial rennet in a pilot plant fermentor

An attempt was made to find out the optimum aeration and agitation rates on the production of bacterial rennet from Bacillus sublilis K-26 using 5% wheat bran medium in a 13 liter fermentor. The enzyme activity and the growth rate were shown to increase with an increase in the rate of agitation. The fermentation experiments carried out at an agitation rate of 400 rpm showed an approximate threefold increase in enzyme activity with a considerable decrease in the fermentation time over those agitated at 200 and 300 rpm. The beneficial effect of a higher oxygen rate was observed for enzyme production occurring at a lower agitation rate. The inoculum activity and the varying amounts of antifoam agent which were added showed no apparent effect either on the total incubation time or on the final enzyme activity. It has been suggested that an agitation rate of 400 rpm with an aeration level of 3000 cc/min are the optimum values for the efficient production of bacterial rennet from B. subtilis K-26 using 5% wheat bran medium in a 13 liter fermentor.     

Growth kinetics ofPseudomonas fluorescens microcolonies within the hydrodynamic boundary layers of surface microenvironments

Computer-enhanced microscopy (CEM) was used to study the growth kinetics of bacterial microcolonies attached to the wall of a continuous-flow slide culture. Image processing increased effective microscope resolution and quantitated colony growth at 10 min intervals. Three growth parameters were used to determine growth rate: the time required for cell fission, the specific rate of increase in cell number, and the specific rate of increase in cell area. Growth rate was initially constant regardless of colony size, as assumed previously in deriving colonization kinetics. However, at low substrate concentrations growth rate varied depending on laminar flow velocity. Growth was flow-dependent at a glucose concentration of 100 mg/liter and flow-independent at a concentration of 1 g/liter. This indicated that the surface microenvironment became substrate-depleted in the absence of sufficient laminar flow velocities and that glucose rather than oxygen was rate limiting.     

Biocalorimetric Studies of the Metabolic Activity of Pseudomonas aeruginosa Aerobically Grown in a Glucose-Limited Complex Growth Medium

Biocalorimetric experiments were performed to investigate the aerobic growth of Pseudomonas aeruginosa, isolated from tannery saline wastewater. Growth factors (pH, Inoculum size, carbon source, temperature, aeration rate, and agitation rate) were optimized in shaker and calorimeter based on the growth of P. aeruginosa and heat generation rates. A limiting value of 0.2% glucose concentration was found to be optimum for the growth of P. aeruginosa in a complex growth medium, and the heat flux (q_r) profiles resulting from the metabolic activity of P. aeruginosa further confirmed this observation. The bacterial growth profile was found to correlate well with the metabolic heat generated. Heat-yield values were calculated for both glucose consumption and the growth of P. aeruginosa from the calorimetric results. Metabolic shifts in substrate uptake from glucose to peptone present in growth medium was observed by the variations in heat-flux profile. The calorimetric data presented in this study should be useful in understanding the behavior of the isolated bacterial strain in degrading complex and mixed substrates commonly observed in tannery saline waste stream, and further to extend the results for scale-up studies.