Disinfection kinetics of Legionella pneumophila by ultraviolet irradiation

2002 ◽  
Vol 46 (11-12) ◽  
pp. 311-317 ◽  
Author(s):  
K. Yamagiwa ◽  
M. Tsujikawa ◽  
M. Yoshida ◽  
A. Ohkawa
Keyword(s):  
Rate Constant ◽  
Legionella Pneumophila ◽  
Ultraviolet Irradiation ◽  
Cell Concentration ◽  
Viable Cell ◽  
Lag Time ◽  
Viable Cell Concentration ◽  
Initial Cell Concentration ◽  
Initial Cell ◽  
Kinetics Of

Disinfection kinetics of Legionella pneumophila by ultraviolet irradiation was investigated. The change in viable cell concentration with exposure time could be divided into three steps: lag step in which little change in viable cell concentration was observed, fast disinfection step and slow disinfection step. The slow disinfection step was not observed at the initial cell concentrations below about 106 cfu/mL. The disinfection kinetics were well described with two parameters; lag time and disinfection rate constant of the fast disinfection step. The effects of UV intensity, temperature and initial cell concentration in the kinetic parameters were investigated. With increasing initial cell concentration, the lag time decreased and the disinfection rate constant increased. The effects of initial cell concentration on the kinetic parameters were considered to be attributed to the decrease in the effective UV irradiation intensity due to the partial shield of UV light by the disinfected cells. The empirical correlations were presented for predicting the lag time and disinfection rate constant. Furthermore, UV disinfection of L. pneuophila in a model hot-tub connected with external irradiation chamber was also discussed.

The comparison of trichloroethylene removal rates by methane- and aromatic-utilizing microorganisms

1998 ◽  
Vol 38 (7) ◽  
pp. 19-24 ◽  
Author(s):  
C.-J. Lu ◽  
C. M. Lee ◽  
M.-S. Chung
Keyword(s):  
Cell Concentration ◽  
Removal Rate ◽  
Carbon Sources ◽  
Batch Reactors ◽  
Initial Cell Concentration ◽  
Removal Rates ◽  
Initial Cell ◽  
Toluene Concentration ◽  
Cell Source ◽  
Removal Efficiencies

The comparison of TCE cometabolic removal by methane, toluene, and phenol utilizers was conducted with a series of batch reactors. Methane, toluene, or phenol enriched microorganisms were used as cell source. The initial cell concentration was about 107 cfu/mL. Methane, toluene, and phenol could be readily biodegraded resulting in the cometabolic removal of TCE. Among the three primary carbon sources studied, the presence of phenol provided the best cometabolic removal of TCE. When the concentration of carbon source was 3 mg-C/L, the initial TCE removal rates initiated by methane, toluene, and phenol utilizers were 1.5, 30, and 100 μg/L-hr, respectively. During the incubation period of 80 hours, TCE removal efficiencies were 26% and 96% with the presence of methane and toluene, respectively. However, it was 100% within 20 hours with the presence of phenol. For phenol utilizers, the initial TCE removal rates were about the same, when the phenol concentrations were 1.35, 2.7, and 4.5 mg/L. However, TCE removal was not proportional to the concentrations of phenol. TCE removal was hindered when the phenol concentration was higher than 4.5 mg/L because of the rapid depletion of dissolved oxygen. The presence of toluene also initiated cometabolic removal of TCE. The presence of toluene at 3 and 5 mg/L resulted in similar TCE removal. The initial TCE removal rate was about 95 μg/L-hr at toluene concentrations of 3 and 5 mg/L compared to 20 μg/L-hr at toluene concentration of 1 mg/L.

Response to phage infection of immobilized lactococci during continuous acidification and inoculation of skim milk

1994 ◽  
Vol 61 (4) ◽  
pp. 537-544 ◽  
Author(s):  
Flavia M. L. Passos ◽  
Todd R. Klaenhammer ◽  
Harold E. Swaisgood
Keyword(s):  
Steady State ◽  
Cell Concentration ◽  
Skim Milk ◽  
Viable Cell ◽  
Free Cell ◽  
Viable Cell Concentration ◽  
Immobilized Cell ◽  
Stainless Steel Mesh ◽  
Immobilized Cell Bioreactor ◽  
Column Bioreactor

SummaryA laboratory scale bioreactor was used for continuous acidification and inoculation of milk with a proteinase-negative, lactose-fermenting strain,Lactococcus lactissubsp.lactisC2S. Calcium alginate-entrapped cells were immobilized on a spiral stainless steel mesh incorporated into a column bioreactor and used to acidify and inoculate reconstituted skim milk. Characteristics of the immobilized cell bioreactor (ICB) were compared with those of a free cell bioreactor (FCB) during challenge with a virulent phage. Steady state biomass and lactate productivities were respectively 25-fold and 12-fold larger with the ICB than with the FCB. The ICB and the FCB were inoculated with the prolate phage c2 at multiplicities of infection of 0·25 and 0·02 respectively. Within 90 min of the infection, the FCB viable cell concentration dropped by five orders of magnitude and never recovered, while the plaque forming units/ml increased dramatically. In the ICB, released cells decreased immediately after infection, but subsequently increased, while the plaque forming units/ml steadily declined, indicating that phage were being washed out of the bioreactor. Productivity of FCB decreased to zero, whereas productivity of the ICB only decreased ∼ 60% and subsequently recovered to its initial steady state value.

scholarly journals Microbes in deionized water: Implications for maintenance of laboratory water production system

2016 ◽  
Author(s):  
Wenfa Ng ◽  
Yen-Peng Ting
Keyword(s):  
Ion Exchange ◽  
Microbial Diversity ◽  
Production System ◽  
Cell Concentration ◽  
Tap Water ◽  
Viable Cell ◽  
Just In Time ◽  
Water Production ◽  
Viable Cell Concentration ◽  
Salt Solutions

Microbes, with their diverse metabolic capabilities and great adaptability, occupy almost every conceivable ecological niche on Earth – thus, could they survive in the oligotrophic (i.e., nutrient-poor) deionized (DI) water that we use for our experiments? Observations of white cauliflower-like lumps and black specks in salt solutions after months of storage in plastic bottles prompted the inquisition concerning the origin and nature of the “contaminants”. Hypothesizing that the “contaminants” may be microbes from DI water, a series of growth experiments was conducted to detect and profile the microbial diversity in fresh DI water - produced on a just-in-time basis by a filter-cum-ion-exchange system with tap water as feed. While microbes could also be present on the surfaces and headspace of the unsterilized polyethylene bottles, investigating whether microbes are present in freshly produced DI water provides a more stringent performance test of the production system. Inoculation of DI water on R2A agar followed by multi-day aerobic cultivation revealed the presence of a wide variety of microbes (total viable cell concentration of ~103 colony forming units (CFU) per mL) with differing pigmentations, growth rates as well as colony sizes and morphologies. Additionally, greater abundance and diversity of microbes was recovered at 30 oC relative to 25 and 37 oC; most probably due to adaptation of microbes to tropical ambient water temperatures of 25 to 30 oC. Comparative experiments with tap water as inoculum recovered a significantly smaller number and diversity of microbes; thereby, suggesting that monochloramine residual disinfectant in tap water was effective in inhibiting cell viability. In contrast, possible removal of monochloramine by adsorption onto ion-exchange resins – and thus, alleviation of a source of environmental stress - might explain the observed greater diversity and abundance of viable microbes in DI water. Collectively, this study confirmed the presence of microbes in fresh DI water – and suggested a possible source of the “contaminants” in prepared salt solutions. Propensity of microbes for forming biofilm on various surfaces suggested that intermittent flow in just-in-time DI water production provided opportunities for cell attachment and biofilm formation in the system during water stagnation, and subsequent dislodgement and resuspension of cells upon water flow. Thus, regular maintenance and cleaning of the production system should help reduce DI water’s microbial load. Additionally, simple and low-cost culture experiments on agar medium can provide a qualitative and semi-quantitative estimate of microbial diversity and viable cell concentration in DI water, respectively, and along with regular monitoring of water resistivity or conductivity, comprise a trio of tests useful for detecting possible contamination, or deterioration of DI water’s chemical and microbiological quality.

scholarly journals THE EFFECT OF THE INITIAL CELL CONCENTRATION UPON SURVIVAL OF BACTERIA AT −22 C

1955 ◽  
Vol 69 (3) ◽  
pp. 244-249 ◽  
Author(s):  
Cecil P. Major ◽  
John D. McDougal ◽  
Arthur P. Harrison
Keyword(s):  
Cell Concentration ◽  
Initial Cell Concentration ◽  
Initial Cell

The Effect of Initial Cell Concentration on Xylose Fermentation by Pichia stipitis

2007 ◽  
pp. 653-662 ◽  
Author(s):  
Frank K. Agbogbo ◽  
Guillermo Coward-Kelly ◽  
Mads Torry-Smith ◽  
Kevin Wenger ◽  
Thomas W. Jeffries
Keyword(s):  
Xylose Fermentation ◽  
Cell Concentration ◽  
Pichia Stipitis ◽  
Initial Cell Concentration ◽  
Initial Cell

scholarly journals The Growth ofMonoraphidiumsp. andScenedesmussp. Cells in the Presence of Thorium

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Juliana Cristina de Queiroz ◽  
Ana Cristina de Melo Ferreira ◽  
Antonio Carlos Augusto da Costa
Keyword(s):  
Cell Concentration ◽  
Direct Count ◽  
Initial Cell Concentration ◽  
Initial Cell ◽  
Count Method ◽  
Low Concentrations ◽  
Direct Counting ◽  
Presence And Absence ◽  
Positive Effect

Toxicity of thorium byMonoraphidiumsp. andScenedesmussp. was studied. Microalgal cultures were inoculated in ASM-1 medium in presence and absence of thorium. Its effect was monitored by direct counting on Fuchs-Rosenthal chamber and with software. The toxicity of thorium over the species was observed for concentrations over 50.0 mg/L. After 30 days,Monoraphidiumcells decreased their concentration from4.23×106to4.27×105and8.57×105 cells/mL, in the presence of 50.0 and 100.0 mg/L of thorium, respectively.Scenedesmussp. cells were more resistant to thorium: for an initial cell concentration of7.65×104 cells/mL it was observed a change to5.25×105and5.12×105 cells/mL, in the presence of thorium at 50.0 and 100.0 mg/L, respectively. This is an indication that low concentrations of the radionuclide favored the growth, and thatScenedesmuscells are more resistant to thorium thanMonoraphidiumcells. The software used for comparison with direct count method proved to be useful for the improvement of accuracy of the results obtained, a decrease in the uncertainty and allowed recording of the data. The presence of thorium suggests that low concentrations have a positive effect on the growth, due to the presence of the nitrate, indicating its potential for ecotoxicological studies.

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