Characterization of the microbial community in an anaerobic ammonium-oxidizing biofilm cultured on a nonwoven biomass carrier

The enrichment and characterization of anaerobic ammonium-oxidizing biofilm cultures are ongoing in our laboratories. Biomass, with a predominately red color, demonstrating simultaneous removal of ammonium and nitrite under autotrophic and anoxic conditions, which is characteristic of anaerobic ammonium-oxidizing planctomycetes, was enriched and maintained for an extended period on a polyester nonwoven carrier. To investigate the bacterial composition of the mature biofilm community, 16S rDNA sequences were amplified by PCR and comparative analyses using DNA databases were conducted. Only one sequence had a notable similarity (92.2%) to that of the first discovered anaerobic ammonium-oxidizing planctomycete and lesser, yet significant, similarities to the 16S rDNA sequences of other recently reported anaerobic ammonium-oxidizing strains. The newly discovered strain (designated KSU-1) reported here was dominant among detectable members of the biofilm community. By fluorescence imaging, KSU-1 was shown to form spherical clusters wrapped in a thin layer of Zoogloea sp. Possible interactions and interdependencies of these two species are discussed with regard to the putative unculturability of the anaerobic ammonium-oxidizing planctomycetes.     

护毛法回收的猪毛通过爆发性膨胀处理的溶解性

本文报导了通过爆发性膨胀增加猪毛溶解度的方法,从而使得保毛脱毛法所回收的猪毛能够得到更有效的利用。     

Contamination levels of PCDDs, PCDFs and Co-PCBs in commercial baby foods in Japan

To examine dioxin contamination in commercial baby foods in Japan, congener analyses of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and coplanar polychlorinated biphenyls (Co-PCBs) were performed on 102 varieties of baby foods obtained from supermarkets in 2001-2002. The toxic equivalent quantity (TEQ) levels for dioxins in samples ranged from < 0.001 to 0.135 pg-TEQ/g wet weight when undetected or trace levels of congeners were taken as zero. Among 102 samples tested, 26 samples exceeded 0.010 pg-TEQ/g. The highest TEQ value was for "sardine, vegetables" (0.135 pg-TEQ/g), followed by "Japanese radish (daikon), sardine" (0.080 pg-TEQ/g). Thus, dioxins were detected at low levels in baby foods containing animal products such as fishes and/or dairy products.     

Treatment capability of an up-flow anammox column reactor using polyethylene sponge strips as biomass carrier

The feasibility of applying a polyethylene (PE) sponge as a biomass carrier in an anaerobic ammonium oxidation (anammox) reactor and its nitrogen removal performance were also investigated. Experiments were carried out in an up-flow column reactor with synthetic inorganic wastewater. Experimental results indicate that reactor containing PE sponge biomass carriers showed a high nitrogen removal capability and exhibited stable performance. In addition, the reactor with 8 strips PE sponge as biomass carrier exhibited greater adaptation capacity compared to that with 6 strips and could achieve a high TN removal rate within a very short period. The ratio of NO₂-N removal and NO₃-N production to NH₄-N removal for the reactor was 1.26:0.21. Furthermore, to investigate the bacterial composition of the mature community, 16S rRNA sequences were amplified by PCR and analyses were conducted using DNA databases. Results showed that a new kind of anammox microorganism (Kumadai-1) was the dominant species in the reactor when using PE sponge as a biomass carrier.     

Multiresidue determination of quinolones in animal and fishery products by HPLC

A simple and rapid multiresidue method was developed for the determination of twelve quinolones (ciprofloxacin, danofloxacin, difloxacin, enrofloxacin, flumequine, marbofloxacin, nalidixic acid, norfloxacin, ofloxacin, orbifloxacin, oxolinic acid and sarafloxacin) in muscle, liver, chicken eggs, milk, prawn and rainbow trout.The quinolones were extracted from a sample with acetonitrile-water (95 : 5). A fifth part of the filtered extract was diluted with water to keep the acetonitrile ratio at ca. 60%, and passed through a C18 mini-column. The eluate was evaporated to dryness, and the residues were dissolved in methanol-water (30 : 70) for HPLC analysis.The quinolones were separated on a Inertsil ODS-3V column (4.6 mm i.d.x250 mm) with a gradient system of 0.1% phosphoric acid-acetonitrile as the mobile phase, with fluorescence detection.No interfering peak was found on the chromatograms of animal and fishery products, except for milk. The recoveries of the quinolones were over 60% from the animal and fishery products fortified at 0.1 microg/g, and the quantification limits of the quinolones were 0.005 microg/g. This proposed method was found to be effective and suitable for the screening of the quinolones in animal and fishery products.     

Noncompetitive inhibition by L-cysteine and activation by L-glutamate of the iron-oxidizing activity of a mixotrophic iron-oxidizing bacterium strain OKM-9

A mesophilic, mixotrophic iron-oxidizing bacterium strain OKM-9 uses ferrous iron as a sole source of energy and L-glutamate as a sole source of cellular carbon. Uptake of L-glutamate into OKM-9 cells is absolutely dependent on ferrous iron oxidation. Thus, the Fe(2+)-dependent L-glutamate uptake system of strain OKM-9 is crucial for the bacterium to grow mixotrophically in iron medium with L-glutamate. The relationship between iron oxidation and L-glutamate transport activities was studied. Iron oxidase containing cytochrome a was purified 9-fold from the plasma membrane of OKM-9. A purified iron oxidase showed one rust-colored band following disc gel electrophoresis after incubation with Fe(2+). The Fe(2+)-dependent L-glutamate transport system was also purified 14.5-fold from the plasma membrane using the same purification steps as for iron oxidase. Fe(2+)-dependent L-glutamate and L-cysteine uptake activities of OKM-9 were 0.36 and 0.24 nmol/mg/min, respectively, when a concentration of 18 mM of these amino acids was used as a substrate. Both uptake activities were completely inhibited by potassium cyanide (KCN), suggesting that cytochrome a in the iron oxidase is involved in the transport process. The iron-oxidizing activity of strain OKM-9 was activated 1.7-fold by 80 mM L-glutamate. In contrast, the activity was noncompetitively inhibited by L-cysteine. The Michaelis constant of iron oxidase for Fe(2+) was 12.6 mM and the inhibition constant for L-cysteine was 41.6 mM. A marked inhibition of iron oxidase by 50 mM L-cysteine was completely reversed by the addition of 60 mM L-glutamate. The results suggest the possibility that iron oxidase has a binding site for L-cysteine and the cysteine first bound to the iron oxidase was replaced by the added L-glutamate.     

Development of a new heterojunction structure (ACJ -HIT) and its application to polycrystalline silicon solar cells

A new solar cell structure named HIT (Heterojunction with Intrinsic Thin layer) has been developed based on new artificially constructed junction (ACJ) technology. In this structure a non-doped a-Si thin layer was inserted between the p(a-Si)/n(c-Si) heterojunction, improving the output characteristics and achieving a conversion efficiency of 18.1%. This structure was applied to cast polycrystalline silicon solar cells of a practical size. A high conversion efficeincy of 13.6% was obtained with a cell size of 10 cm × 10 cm using various technologies, including hydrogen plasma passivation.     

Modification of bismaleimide resin by poly(propylene phthalate), poly(butylene phthalate) and related (co)polyesters

Aromatic polyesters were prepared and used to decrease the brittleness of the bismaleimide resin composed of 4,4′-bismaleimidediphenyl methane (BMI) and o,o′-diallyl bisphenol A (DBA) (Matrimid 5292 resin). The aromatic polyesters included poly(propylene phthalate) (PPP), poly(2,2-dimethylpropylene phthalate) (PDPP), poly(butylene phthalate) (PBP) and poly(butylene phthalate-co-butylene terephthalate) (50mol% terephthalate unit) (PBPT). The polyesters were effective modifiers for decreasing the brittleness of the bismaleimide resin. For example, inclusion of 20wt% PPP (MW 18700) led to 50% increase in the fracture toughness (K_IC) with retention of flexural properties and a slight loss of the glass transition temperature, compared with the mechanical and thermal properties of the unmodified cured bismaleimide resin. Micro-structures of the modified resins were examined by scanning electron microscopy and dynamic viscoelastic analysis. The thermal stability of the modified resins was slightly lower than that of the unmodified resin as determined by thermogravimetric analysis. The toughening mechanism is discussed in terms of the morphological and dynamic viscoelastic behaviour of the modified bismaleimide resin system. © 1998 SCI.