Tatsuo Yagishita

Effect of ammonium addition on methanogenic community in a fluidized bed anaerobic digestion.

After immobilization of anaerobes on carbon felt in a fluidized-bed anaerobic digester at an ammonium concentration of 500 mg N/l, the results of real-time PCR analysis indicated that the cell densities of the immobilized methanogens and bacteria increased compared with those of the free-living methanogens and bacteria in the original anaerobically digested sewage sludge, respectively. The results of the clone analysis of the original sludge suggested that the major methanogens were Methanosaeta sp. and the members of the order Methanomicrobiales, and that after immobilization, these were changed to Methanobacterium and Methanosarcina sp. The results of real-time PCR analysis also showed that the ratio of the Methanosaeta sp. in the methanogenic archaea decreased from 58.2% to 0.3% after the immobilization. Methane production decreased at ammonium concentrations of greater than 6000 mg N/l. The results of real-time PCR analysis indicated that the cell density of the immobilized archaea decreased at ammonium concentrations of greater than 3000 mg N/l. On the other hand, the cell density of the immobilized bacteria did not decrease at an ammonium concentration of 6000 mg N/l, but decreased at that of 9000 mg N/l. The major methanogenic clones immobilized on the carbon felt at an ammonium concentration of 3000 or 6000 mg N/l were Methanobacterium sp. The present results indicated that methanogens were relatively more sensitive to ammonium than bacteria.

Microalgal cultivation in a solution recovered from the low-temperature catalytic gasification of the microalga

Microalgal cultivation in a solution recovered from the low-temperature catalytic gasification of the microalga itself was studied. The growth of Chlorella vulgaris in 75-300-fold diluted recovered solution containing phosphate, magnesium ions and micro-elements was comparable to that in the standard culture medium. It was suggested that C. vulgaris could use ammonium in the recovered solution as its nitrogen source and at the same time could provide a source of biomass which was recycled via gasification.

Effects of glucose addition and light on current outputs in photosynthetic electrochemical cells using Synechocystis sp. PCC6714

The effects of glucose addition and light on the current outputs in electrochemical cells using a cyanobacterium Synechocystis sp. PCC6714 were investigated under photo- and chemoheterotrophical conditions. The addition of glucose to the anode solutions of the electrochemical cells resulted in a rapid increase in the current outputs under both light and dark conditions. Although the coulombic outputs were almost the same between under light and dark conditions, the rate of glucose consumption was faster under illumination than in the dark. The total sugar content in the cells of strain PCC6714 increased with the addition of glucose and the total sugar accumulated remained intact during the discharge under illumination, while it decreased gradually in the dark. When the light was switched off after the addition of glucose, the current output markedly increased. The coulombic outputs obtained after darkening were 10 to 80 times larger than that obtained by the addition of glucose under the continuous light or dark conditions. Synechocystis sp. completely incorporated 0.14 mM and 0.42 mM glucose for 1 h and 3 h, respectively, under illumination. There was no difference in the coulombic outputs between 1 h and 12 h illumination times in the electrochemical cells with 0.14 mM glucose. When the light was switched off after 1 h illumination in the electrochemical cells with 0.42 mM glucose, the coulombic output obtained from the electrochemical cell was lower than that in the electrochemical cell with 12 h illumination. This indicates that the current output was produced with higher efficiency with glucose incorporated under illumination than that in the case of glucose incorporated after darkening. The highest coulombic yield of 54% in this experiment was obtained by darkening in the electrochemical cell with 0.14 mM glucose.

Performance of photosynthetic electrochemical cells using immobilized Anabaena variabilis M-3 in discharge/culture cycles

Abstract The performance of photosynthetic electrochemical cells using Anabaena variabilis M-3 immobilized within alginate beads was investigated during repeated discharge and culture cycles of 10-h each. The effect of the light intensity during the culture periods on the duration of the current output and the recovery of endogenous total sugar in the Anabaena cells was examined. Compared with continuous discharge operation, the duration of the current output was extenced by 10 times when the electrochemical cell was operated under 10-h discharge (dark)/culture (light) cycles with a light intensity of 100 W/m 2 during the culture periods. The conversion efficiency of light energy into electricity was about 0.2% under these conditions.

Treatment of liquid fraction separated from liquidized food waste in an upflow anaerobic sludge blanket reactor.

Thermochemical liquidization as a pretreatment for anaerobic digestion of food waste was studied using a laboratory-scale upflow anaerobic sludge blanket (UASB) reactor for a period of 82 d. Model food waste (approximately 90 wt% moisture content) was thermochemically liquidized at 175 degrees C for 1 h. The liquidized food waste was separated into a solid phase (6-10 wt%) and a liquid phase (85-89 wt%). The diluted liquid phase was continuously treated by anaerobic digestion using a UASB reactor at 35 degrees C. The volumetric loading rate was increased stepwise to 6.4-7.2 g total organic carbon (TOC)/l-reactor/d. Methane production was found to be approximately 0.35-0.61 l/g-TOC removed. The range of TOC removal efficiencies was 67-69% at an influent TOC concentration of 10.1-11.1 g/l and a volumetric loading rate of 4.8-5.3 g-TOC/l-reactor/d. This treatment process using an UASB reactor could be suitable for resource recovery from food waste.

Behavior of glucose degradation in Synechocystis sp. M-203 in bioelectrochemical fuel cells.

Glucose metabolism in Synechocystis of M-203 under heterotrophic condition was studied with the electrochemical cells. By the addition of glucose, the voltage output rapidly increased under illumination, and in the dark substantial voltage output was sustained stably for 20 h of discharge. The addition of the glucose analogue 3-O-methyl-d-glucose did not change the current output both in the light and the dark, indicating that added glucose was transported into Synechocystis cells and was consumed to produce electricity. An inhibitor, carbonyl cyanide-m-chlorophenylhydrazone was induced the increase in the current output under illumination, while 3-(3,4-dichlorophenyl)-1, 1-dimethylurea partially inhibited the current output.

Wastewater treatment and poly-β-hydroxybutyrate production using lighted upflow anaerobic sludge blanket method

We investigated the performance of a lighted upflow anaerobic sludge blanket (LUASB) reactor for wastewater treatment and poly-beta-hydroxybutyrate (PHB) production. Phototrophic bacteria were induced from UASB (upflow anaerobic sludge blanket) granules under light conditions (100 microE.m(-2).s(-1)). The ammonium and phosphate ion removal efficiencies of the LUASB reactor were higher than those of the UASB reactor. The difference in the results from runs under light and dark conditions suggested that the ammonium and phosphate ion removal efficiencies were improved by increasing the amount of phototrophic bacteria in the LUASB reactor. The average production rate of PHB from the biomass in the effluent from the LUASB reactor was 6.6-14.0 mg.l(-1)-reactor.d(-1) using acetate-based media and the average PHB content based on the dry bacterial biomass was 15.1-25.3%. The PHB concentration increased by reincubation of the effluent from the LUASB reactor with sodium acetate under light conditions. The UASB granular sludge can decompose a variety of organic substances and in addition the LUASB method can remove ammonium and phosphate ions. The LUASB method thus appears to be appropriate for wastewater treatment and production of phototrophic bacteria and PHB from various wastewaters.

Photosynthetic bio-fuel cells using cyanobacteria

Effects of glycogen and glucose on the current outputs have been studied in photosynthetic bio-fuel cells using two kinds of cyanobacteria, Anabaena variabilis M-3 and Synechocystis sp. M-203, and 2-hydroxy-1,4-naphthoquinone. In the bio-fuel cell using Anabaena variabilis M-3, by repeating discharge-culture operation, the lifetime of the bio-fuel cell extended to net 80 hours, although the current output was sustained only for 10 hours under the condition of continuously running. In the case using Synechocystis sp. M-203, the current outputs both in the light and dark substantially increased by the addition of glucose to the anode solutions, indicating that glucose was transported into Synechocystis cells and was consumed to produce electricity.

Lighted Upflow Anaerobic Sludge Blanket

The upflow anaerobic sludge blanket (UASB) method has been developed as an efficient anaerobic wastewater treatment process; however, the performance of this process in the removal nitrogenous compounds and phosphate is not high. Here, we present the water treatment performance of a lighted upflow anaerobic sludge blanket (LUASB) reactor and propose a novel LUASB concept. A population of phototrophic bacteria was induced from UASB granules under light conditions (100 microE x m(-2) x s(-1)). The ammonium and phosphate ion removal efficiencies of the LUASB reactor were higher than those of a UASB reactor. The difference in the results from runs under light and dark conditions suggests that the efficiencies of ammonium and phosphate ion removal were improved by an increase in the phototrophic bacteria in the LUASB reactor. The UASB granule can decompose a variety of organic substances; therefore, the LUASB method could also be effective for producing phototrophic bacterial biomass and polyhydroxyalkanoates (PHAs) from various wastewaters.

Anaerobic treatment of liquidized organic wastes

Kitchen garbage and dewatered sewage sludge were thermochemically liquidized at 175 °C and 4 MPa with 1 h of holding time. The liquidized garbage and sludge were separated into liquid and solid fractions, respectively. The diluted liquid fraction of the liquidized garbage and sewage sludge were continuously anaerobically digested using upflow anaerobic sludge blanket method. The digestion ratio of the liquid fraction separated from the liquidized garbage was 74–75% at the added TOC concentration of 17.0 g·l−1 and the TOC loading rate of 1.8–2.8 mg·cm−3-granule·day−1. The digestion ratio in the liquid fraction separated from the liquidized sewage sludge was 57–75% at the added TOC concentration of 7.9 g·l−1 and the TOC loading rate of 2.2 mg·cm−3-granule·day−1. The solid fraction could be processed to refuse derived fuel according to its decreased moisture content. The energy balances of this treatment process for kitchen garbage and sewage sludge were initially analyzed to be better than those of direct incineration.