Initial bacterial concentration

Fig. 17.1 Initial rate of bacterial inactivation as a function of Ti02 concentration, (a) For an initial bacterial concentration of 107 (filled square) and 105 CFU mL-1 (filled diamond) at 1,000W m-2. (b) For an initial bacterial concentration of 107 at 1,000 Wm-2 (filled square) and 400 Wm 2 (filled circle). Solar simulator...

The aim of this section is to quantify the influence of some operating parameters such as flow rate, catalyst concentration, initial bacterial concentration, and reactor volume. These parameters affect reactor efficiency evaluation and therefore subsequent optimization of the disinfection system. 

Figure 11.4a,b show the microcapsules as initially formed with Listeria monocytogenes and Staphylococcus aureus attached to the forming polyamide capsule wall. The bacteria, respectively rod and coccoid shaped, were clearly visible on the outside surface of the capsules when labelled with ethidium bromide, as evidenced by confocal optical sections. Variation of the initial bacterial concentration and... 

Fig. 11.2 Survival of Enterococcus faecalis exposed to a fluoroquinolone for 4 h at 37°C. Three initial bacterial concentrations were studied, 107cfu/ml ( ) 10 ctli/ml (A) and 105 cfu/ml (O). This clearly demonstrates a paradoxical effect (increasing antimicrobial concentrations past a critical level reveal decreased killing), and the effects of increased inoculum densities on subsequent killing (courtesy of Dr Z. Hashmi).

In addition to reducing the inhibition constant, the initial density for the o-xylene degrading bacteria at the column inlet had to be reduced from the value of 1 jimol cell carbon per cm column material as used in Experiment 1 to 0.4 pmol cell carbon per cm. Otherwise the higher o-xylene concentrations for the initial phase of Experiment 2 could not have been reproduced. Different initial bacterial concentrations are not unrealistic, as different columns (although of the same type) were used for the two experiments. 

Initial bacterial concentration = 3.2x 105CFU/fabric (CFU = colony forming units) (Chang et al., 2008)... 

Kinetic models as a function of initial substrate concentration and bacterial cell density (From Alexander, 1985. Reprinted with permission from the American Chemical Society). 

Note that the initial concentration of bacteria in Fig. 17.7a is 1,000 times higher than that of Fig. 17.7b. A low bacterial load requires less time to reach a bacterial concentration below the detection limit (1 CFUmL-1). However, the efficiency of the photolytic and photocatalytic disinfection rates are higher for a high concentration of bacteria (like 106—107 CFUmL-1) than for small concentration (102 CFU mL-1) as explained in the Sect. 17.4.1 (Rincon and Pulgarin 2004b). 

Recently, WPCs have been used as carriers for biopolymers and microorganisms (Fig. 26.4). Robledo-Ortiz et al. [50] used a composite material of recycled HDPE and agave fibers for bacterial immobilization. According to the results reported, the natural adhesion of Pseudomonas putida FI onto the composite surface is strongly affected by temperature, pH, ionic strength, and initial biomass concentration. Vdzquez et al. [51] coated the same material (agave fibers/HDPE) with chitosan to be applied in heavy-metal adsorption. These studies showed that composite materials represent an attractive low-cost recycled support for bacterial and biopolymers with potential applications in biotechnological and environmental cleanup processes. 

Fig. 6.12 Survival curve of E. coli JM 109 over exposure time to cast and electrospun P(3HB)-50 wt% TiOi films under different illumination sources. The initial cell concentration used was 3.6 X 10 CPU mL . Bacterial suspension was sampled at 3 h intervals for 12 h. The samples were spread plated on LB agar and incubated at 37 °C for 24 h...

As a first step in addressing this challenging problem, we evaluated the possibility of determining the minimum lethality delivered to the center of a particulate, with known initial precursor concentrations, from the marker yields and the kinetic data obtained in the laboratory under an isothermal condition. The mathematical model used (Ross, 1993) yields bacterial destruction from the fractional marker yield as long as the peak temperature of the temperature pulse is provided. 

Outdated but other vise clean and sterile platelets vere used for the experiments. Suspensions of different bacteria vere prepared in sterile saline (0.85% NaCl) and diluted to get different initial concentrations from 1 to 10 colony-forming units (CPU) per milliliter. Samples of 1 ml of PLTs vith 0.1 ml inoculation culture at four bacterial concentrations vere prepared. Several samples vith different bacteria-infected PLTs vere transferred into the calorimeter vessels. The measurements vere performed at (37 0.02) °C for several days. 

Pseudomonas that cause skin infections, within 30 s by 2 ppm FAC at pH 7.4 (62). In a series of tests under stabilized conditions (50—100 ppm cyanuric acid), an initial concentration of 3 ppm FAC could not provide water that met the NSPI standards for bacteria or the maintenance of at least a 2 ppm FAC residual. Increasing the initial FAC to 4 ppm resulted in the bacterial criteria being met 100% of the time even when the FAC residual fell below 1 ppm. For heavy bather loads an initial FAC > 4 ppm is recommended. 

Fluorides. Most woddwide reductions in dental decay can be ascribed to fluoride incorporation into drinking water, dentifrices, and mouth rinses. Numerous mechanisms have been described by which fluoride exerts a beneficial effect. Fluoride either reacts with tooth enamel to reduce its susceptibihty to dissolution in bacterial acids or interferes with the production of acid by bacterial within dental plaque. The multiple modes of action with fluoride may account for its remarkable effectiveness at concentrations far below those necessary with most therapeutic materials. Fluoride release from restorative dental materials foUow the same basic pattern. Fluoride is released in an initial short burst after placement of the material, and decreases rapidly to a low level of constant release. The constant low level release has been postulated to provide tooth protection by incorporation into tooth mineral. 

There are a wide variety of initial sources of NOs for the ice sheets, including bacterial emissions, biomass burning, photochemical reactions, and lightning. These are generally low-mid-latitude continental sources. This very complicated mixed source renders interpretations of ice-core NOJ" concentrations difficult. A further complication results from possible limitations on delivery of NOT to ice-core sites by atmospheric circulation, due to the large distance from... 

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