Laboratory studies on nitrogen and phosphorus removal from swine wastewater by iron electrolysis.

Biological process-free ("Bio-free") treatment of swine wastewater (pH 8.5 or above) for the removal of nitrogen and phosphorus was examined. In this study centrifugal separation of solids and liquids was followed by iron electrolysis, which enables removal of nitrogen and phosphorus when iron is set as the cathode and anode, respectively. The manner in which the treatment efficiency varies according to the current ratio of iron anode to iron cathode (Rac) was investigated. Nitrogen was removed to a level below 60 mg l(-1) in a 3-h treatment when Rac was above 75% and phosphorus was removed to a level below 8 mg l(-1) in the same period, irrespective of Rac. Nitrogen removal efficiency was 60 kWh kg-N(-1) , which is 6 times higher than that of the same electrolytic treatment when used after aerobic biological treatment ("Post-bio").

Determination of the amount of native structural bacteriorhodopsin in purple membrane Langmuir-Blodgett films by a spectroscopic surface denaturation quantifying technique.

Purple membrane (PM) shows denaturation when spread over an air/water interface. We established a technique, which we call the spectroscopic surface denaturation quantifying (SSDQ) technique, that uses infrared linear dichroism to determine the amount of native structural bacteriorhodopsin (BR) in PM Langmuir-Blodgett (LB) films. Using the SSDQ technique we found that the conformational change after surface denaturation of BR was the same as that caused by ethanol treatment. By extrapolating the data of the amount of non-denatured BR molecules in PM LB films vs. the area of a single BR molecule on an air/water interface, we also found that the surface area of a single non-denatured BR molecule was 11.5 nm2, which is consistent with that determined by high-resolution electron cryo-microscopy and electron diffraction (EMD). These results demonstrate that the SSDQ technique is effective in quantifying the amount of native structural BR in PM LB films. The SSDQ technique is also applicable to other types of protein consisting of alpha-helical conformation.

Direct reconstitution of bacteriorhodopsin into planar phospholipid bilayers--detergent effect.

This paper describes how the structure and concentration level of a detergent used for substitution after bacteriorhodopsin (bR) solubilization affect the reconstitution of the bR into phospholipid planar bilayers. A direct insertion method was used for the bR reconstitution into the bilayers. Two detergents representing the two major types were used: sodium deoxycholate with a cholane-ring structure, and octylglucoside with a linear (or chain) structure. We then characterized the reconstitution for the two detergents by considering the detergent separation profiles and the photocurrent variations upon addition of lanthanum chloride and the protonophore FCCP (carbonylcyanide-p-trifluoromethoxyphenylhydrazone). We found that for successful transmembrane reconstitution of bR the detergent with the cholane-ring structure was preferable to that with the linear structure when the detergent concentration was above its critical micellar concentration. This preference was explained by the ease with which the detergent with the cholane-ring structure was removed from protein compared to that with the linear structure. Finally, we proposed a scheme for the reconstitution of the protein.

Oscillatory phenomena in model membrane: electrical oscillation in lipid-impregnated membrane filter induced by alamethicin and controlled by bacteriorhodopsin.

A lipid-impregnated membrane filter was able to show reproducibly of an electrical oscillation under constant current stimulation when alamethicin and protamine were present in the chamber whose salt concentration was higher than the other and the membrane was left for about 12 h. In addition, bacteriorhodopsin, which is a light-activated proton pump, was found to control the oscillation. The oscillatory phenomenon was considered to be driven by the alternating change in the ion-selectivity of the membrane between cation and anion. Impedance measurement indicated the existence of lipid rearrangement which might prepare an environment for both alamethicin and protamine to cause the oscillation.