Algal photosynthetic aeration increases the capacity of bacteria to degrade organics in wastewater.

Wastewater treatment is an energy-intensive process and a net emitter of greenhouse gas emissions. A large fraction of these emissions is due to intensive aeration of aerobic bacteria to facilitate break-down of organic compounds. Algae can generate dissolved oxygen at levels in excess of saturation, and therefore hold the potential to partially displace or complement mechanical aeration in wastewater treatment processes. The objective of this study was to develop an internally consistent experimental and modeling approach to test the hypothesis that algal photosynthetic aeration can speed the removal of organic constituents by bacteria. This framework was developed using a simplified wastewater treatment process consisting of a model bacteria (Escherichia coli), a model algae (Auxenochlorella protothecoides), and a single carbon source that was consumable by bacteria only. This system was then tested both with and without the presence of algae. A MATLAB model that considered mass transfer and biological kinetics was used to estimate the production and consumption of O2 and CO2 by algae and bacteria. The results indicated that the presence of algae led to 18-66% faster removal of COD by bacteria, and that roughly one-third of biochemical oxygen demand was offset by algal photosynthetic aeration.

Water-soluble oligomer formation from acid-catalyzed reactions of levoglucosan in proxies of atmospheric aqueous aerosols.

Herein is reported the first laboratory observation of the oligomerization of levoglucosan studied under atmospherically relevant conditions. Oligomers up to 1458 Da (9-mer) were measured by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. A rational mechanism is proposed based on both the acid-catalyzed cationic ring-opening of levoglucosan and nucleophilic attack of ROH from levoglucosan on the hemi-acetal carbon to produce pyranose oligomers through the formation of glycosidic bonds. Oligomer formation is further supported by attenuated total reflectance Fourier transform infrared spectroscopy. Levoglucosan is a viable tracer for biomass burning aerosols, and the observed products may serve as secondary tracers for these types of aerosols, possibly providing additional information to facilitate source apportionment and better understand atmospheric processing of the aerosol parcel. Also, the processes supported here may contribute to the saccharide character of humic-like substances, which are proposed to be formed through the atmospheric processing of biomass burning aerosols.

Benzyl alcohol-induced destabilization of interferon-gamma: a study by hydrogen-deuterium isotope exchange.

The destabilizing effect of a multidose preservative, benzyl alcohol, on IFN-gamma was investigated. Hydrogen-deuterium isotope exchange (HX) detected by mass spectrometry (MS) was used to detect tertiary structure changes and measure global unfolding rates. The experiments showed that tertiary structure changes previously reported using circular dichroism may involve only a limited portion of the protein with the hydrophobic core of the protein remaining intact. Protein unfolding rates measured by hydrogen exchange were very sensitive to benzyl alcohol concentration, and increased markedly when salt was also added. Dynamic light scattering and size-exclusion chromatography showed that a small fraction of the protein formed large aggregates during the first few days. Measurements at longer incubation times (up to 8 days) showed that a significant fraction of protein was trapped in a structure less protected from hydrogen exchange, but not completely unfolded. This fraction of protein may be responsible for the irreversible loss of activity observed in earlier studies.

Aprotinin conformational distributions during reversed-phase liquid chromatography. Analysis by hydrogen-exchange mass spectrometry.

Hydrogen-exchange mass spectrometry analysis of the stable protein aprotinin during reversed-phase liquid chromatography shows both native and unfolded protein. The behavior is consistent with only two conformational states, a near-native state and a fully solvent-accessible state, with reversible interchange of species within and between the mobile and stationary phases. The amount of unfolded form is greater on C18 relative to C4 alkyl modified silica surfaces. The addition of (NH4)2SO4, Na2SO4, NaCl, or NaSCN to the mobile phase stabilized native conformation on the chromatographic surface, especially on the C4 media. Finally, the retention and the proportion of denatured form increases with added salts in anorder consistent with the lyotropic series, but reversed from that observed for small molecules.