Contaminant-Activated Visible Light Photocatalysis.

Pristine titanium dioxide (TiO) absorbs ultraviolet light and reflects the entire visible spectrum. This optical response of TiO has found widespread application as white pigments in paper, paints, pharmaceuticals, foods and plastic industries; and as a UV absorber in cosmetics and photocatalysis. However, pristine TiO is considered to be inert under visible light for these applications.

Influence of Suwannee River humic acid on particle properties and toxicity of silver nanoparticles.

Adsorption of natural organic matter (NOM) on nanoparticles can have dramatic impacts on particle dispersion resulting in altered fate and transport as well as bioavailability and toxicity. In this study, the adsorption of Suwannee River humic acid (SRHA) on silver nanoparticles (nano-Ag) was determined and showed a Langmuir adsorption at pH 7 with an adsorption maximum of 28.6 mg g(-1) nano-Ag.

Polyhydroxy fullerenes (fullerols or fullerenols): beneficial effects on growth and lifespan in diverse biological models.

Recent toxicological studies on carbon nanomaterials, including fullerenes, have led to concerns about their safety. Functionalized fullerenes, such as polyhydroxy fullerenes (PHF, fullerols, or fullerenols), have attracted particular attention due to their water solubility and toxicity. Here, we report surprisingly beneficial and/or specific effects of PHF on model organisms representing four kingdoms, including the green algae Pseudokirchneriella subcapitata, the plant Arabidopsis thaliana, the fungus Aspergillus niger, and the invertebrate Ceriodaphnia dubia.

Optical heating and rapid transformation of functionalized fullerenes.

Irradiating single-walled carbon nanotubes can lead to heat generation or ignition. These processes could be used in medical and industrial applications, but the poor solvent compatibility and high aspect ratios of nanotubes have led to concerns about safety. Here, we show that certain functionalized fullerenes, including polyhydroxy fullerenes (which are known to be environmentally safe and to have therapeutic properties) are heated or ignited by exposure to low-intensity (<10(2 ) W cm(-2)) continuous-wave laser irradiation.

Influence of alternating oxic/anoxic conditions on growth of denitrifying bacteria.

Denitrifying bacteria that are switched from oxic to anoxic conditions can experience diauxic lag, which is the time required for re-synthesis of nitrate reductase and other denitrifying enzymes. Pseudomonas denitrificans were exposed to alternating oxic/anoxic phases in a continuous flow reactor with either 4-h or 8-h anoxic phase lengths, in comparison to a measured diauxic lag of 9.5h following steady-state oxic conditions.

Effect of periplasmic nitrate reductase on diauxic lag of Paracoccus pantotrophus.

Paracoccus pantotrophus expresses two nitrate reductases-membrane bound nitrate reductase (Nar) and periplasmic nitrate reductase (Nap). In growth experiments with two denitrifying species (Paracoccus pantotrophus and Alcaligenes eutrophus) that have both Nap and Nar and two species (Pseudomonas denitrificans and Pseudomonas fluorescens) with Nar only, it was found that diauxic lag is shorter for bacteria that express Nap. In P.

Effect of UVA irradiance on photocatalytic and UVA inactivation of Bacillus cereus spores.

The current study is the first to delineate the contribution of photocatalysis to inactivation of Bacillus cereus endospores on dry surfaces over a broad range (0-153W/m(2)) of UVA irradiance. Inactivation of spores at low UVA irradiance (30W/m(2)) was primarily due to photocatalysis, whereas at higher UVA irradiance inactivation was primarily due to UV alone. A linear relationship between UVA irradiance and the rate of spore inactivation was observed in the absence of photocatalyst.

Determination of diauxic lag in continuous culture.

A procedure was developed to characterize diauxic lag of bacteria switching between electron acceptors in continuous culture. In this procedure, a virtual batch growth curve is developed by integrating the time-dependent net specific growth rates of bacteria observed under continuous flow conditions. The length of diauxic lag and the highest net specific growth rate following lag are conveniently estimated from the virtual batch curve.

Estimation of nitrate reductase enzyme parameters in activated sludge using an extended Kalman filter algorithm.

This paper demonstrates an application of the extended Kalman filter to a wastewater plant using real process data to estimate parameters in a semi-mechanistic model. This technique for parameter identification allows a semi-mechanistic model developed for pure cultures to be applied to a mixed culture population where isolation of enzyme kinetic parameters is not practical. This paper demonstrates an application in which a wastewater treatment facility with three physical unit operations and an unusual operating profile is modeled as 11 reactor units with recirculation streams.

Dominance of endospore-forming bacteria on a Rotating Activated Bacillus Contactor biofilm for advanced wastewater treatment.

The bacterial diversity inherent to the biofilm community structure of a modified rotating biological contactor wastewater treatment process, referred to as the Rotating Activated Bacillus Contactor (RABC) process, was characterized in this study, via both culture-dependent and culture-independent methods. On the basis of culture-dependent methods, Bacillus sp. were found to exist in large numbers on the biofilm (6.

Effect of carbon substrate on electron acceptor diauxic lag and anoxic maximum specific growth rate in species with and without periplasmic enzyme.

The effect of oxidation state of carbon substrate on the diauxic lag of facultative anaerobic denitrifying bacteria growing aerobically upon switching to anoxic growth was studied. Also studied was the effect on the anoxic maximum specific growth rate. Two pure bacteria cultures were used, Paracoccus pantotrophus, denitrifying bacteria containing a periplasmic nitrate reductase (Nap), and Pseudomonas denitrificans, denitrifying bacteria lacking the periplasmic nitrate reductase.

Enhancement of titanium dioxide photocatalysis by water-soluble fullerenes.

Fullerenes are known for their unique electronic properties including high electron affinity. Although use of fullerenes for scavenging photo-generated electrons from titanium dioxide particles has been demonstrated, no attempts have been made to utilize the unique properties of fullerenes to increase the efficacy of photocatalysis. The present study has demonstrated that a mixture of water-soluble polyhydroxy fullerenes (PHF) and titanium dioxide (anatase polymorph) enhances photocatalytic degradation of organic dye.

A simple model for diauxic growth of denitrifying bacteria.

A simple model has been formulated to simulate diauxic growth of denitrifying bacteria. It is capable of fitting the experimental results of batch growth experiments with Pseudomonas denitrificans under various conditions. It successfully predicts the observed lags when a pure culture of this bacterium switches from oxygen to nitrate as terminal electron acceptor.

Structured model for denitrifier diauxic growth.

We present a model for diauxic growth of denitrifying bacteria in which nitrate reductase synthesis kinetics dominate the overall growth kinetics. The model is based on the assumption of the existence of a nitrate respiration operon, thereby linking the rate of nitrate uptake to the activity of nitrate reductase. We show that this approach can model diauxic growth of Pseudomonas denitrificans by conducting experiments in which nitrate reductase activity was measured during both lag and ensuing exponential growth phases.

Nitrite inhibition of aerobic growth of Acinetobacter sp.

Nitrite inhibition of Acinetobacter sp. growing under aerobic conditions was studied. Specific growth rates under non-limiting concentrations of acetate and dissolved oxygen averaged 0.