Osamu Ichihashi

Effect of lignocellulose-derived inhibitors on growth of and ethanol production by growth-arrested Corynebacterium glutamicum R.

ABSTRACT In cellulosic ethanol production, pretreatment of a biomass to facilitate enzymatic hydrolysis inevitably yields fermentation inhibitors such as organic acids, furans, and phenols. With representative inhibitors included in the medium at various concentrations, individually or in various combinations, ethanol production by Corynebacterium glutamicum R under growth-arrested conditions was investigated. In the presence of various inhibitors, the 62 to 100% ethanol productivity retained by the C. glutamicum R-dependent method far exceeded that retained by previously reported methods.

Removal and recovery of phosphorus as struvite from swine wastewater using microbial fuel cell

Air-cathode single chamber microbial fuel cells (MFCs) were operated with swine wastewater. The maximum power density, the maximum current density, the average value of COD-removal efficiency, and the coulombic efficiency were 1-2.3 W/m(2), 6.0-7.0 A/m(2), 76-91%, and 37-47%, respectively. During operation, 70-82% of the phosphorus was removed from the influent, and some precipitations were observed on the surface of the liquid side of the cathodes. The amount of phosphorus contained in these precipitates was estimated to be equivalent 4.6-27% of the influent. The main component of these precipitates was revealed by X-ray diffraction analysis to be struvite. Furthermore, our results indicate that phosphorus in suspended solid form was first dissolved, and then precipitated on the cathode. By scanning electron microscope observation, the morphology of the precipitates was irregularly shaped, including crystals with hexagonal cross-section surfaces, and was different from the familiar needle-like ones. These results indicate that simultaneous recovery of electrical power and phosphorus from wastewater by microbial fuel cell is possible.

Phosphorus recovery from artificial wastewater by microbial fuel cell and its effect on power generation

The effects of ammonium (NH4) and magnesium (Mg) on the precipitation of phosphorus in artificial wastewater by an air-cathode single-chamber microbial fuel cell were investigated. When both NH4 and Mg were added to the wastewater, phosphorus was precipitated as struvite. Almost no precipitation occurred with the addition of only NH4, while phosphorus was precipitated as cattiite with the addition of only Mg. However, the amount of precipitate was less than that observed in experiments in which NH4 was also added. As the amounts of NH4 and Mg were increased, more precipitate was observed. Precipitated phosphorus on the cathode was recovered by dissolution in Milli-Q water and MES buffers. It was discovered that the formation of a precipitate reduced the performance of the cathode. Dissolution treatment caused the performance of the cathodes to increase to their initial level.

Deterioration in the Cathode Performance during Operation of the Microbial Fuel Cells and the Restoration of the Performance by the Immersion Treatment

Microbial fuel cells were operated with synthetic wastewater containing phosphate as a buffer and sodium acetate as a substrate. Linear sweep voltammetry showed the deterioration in the performance of the cathodes after operation. The immersion of the deteriorated cathodes in Milli-Q water, acidic and basic buffer solutions improved the performance. The treatment in the acidic buffer solution restored the performance of the cathode to the extent almost equivalent to that of a new cathode, whereas the treatment in Milli-Q water and the basic buffer solution did not restore the performance to that extent. The improved performance by the immersion in Milli-Q water or the buffer solutions indicates that the water-soluble components are responsible for the deterioration in the cathode performance. Almost complete recovery of the performance in acidic condition suggests that salts that are highly soluble in acidic condition, and poorly soluble in basic condition are responsible for the deterioration. The analysis of the eluted substances in the immersion solution suggests that these salts contained phosphorus, magnesium and calcium in a high concentration.