Effect of modification of soybean lipoxygenase-1 with N-bromosuccinimide on linoleate oxidation,pigment bleaching and carbonyl production

Essential tryptophan residues were specifically modified in soybean lipoxygenase-1 by N-bromosuccinimide (NBS). Both linoleate oxidation and pigment bleaching (β-carotene or chlorophyll a) activities were significantly reduced with the modified enzyme under aerobic conditions. However, the effect on the reduction of linoleate oxidation was more marked. Pigment bleaching under anaerobic conditions was almost completely blocked with the modified enzyme. On the basis of spectral studies it was elucidated that soybean lipoxygenase-1 contains two essential tryptophan residues in its active site.     

Enzymatic bleaching of kraft pulp by xylanase from Aspergillus sydowii SBS 45

Crude xylanase from Aspergillus sydowii SBS 45 was tested for enzymatic bleaching of kraft (Decker) pulp. After optimization of three parameters, consistency of pulp, retention time and enzyme dose, considerable increase in the release of UV and visible absorbance spectra of materials and reducing sugars was observed, which clearly indicated the action of xylanase on pulp. Final brightness of pulp was increased from 29.42 to 70.42% and kappa number was reduced from 15.93 to 1.61, when 25 U of xylanase was given with a retention time of 5 h and at a consistency of 10%. When 10 U g⁻¹ xylanase was given, 14.3% elemental chlorine and 14.3% H₂O₂ could be reduced and when 25 U g⁻¹ xylanase was given 14.3% elemental chlorine and 28.6% H ₂O₂ could be reduced thereby retaining the brightness at control level.     

Herbicides which inhibit photosystem II or produce chlorosis and their effect on production and transformation of pigments in etiolated radish seedlings (Raphanus sativus)

Abstract The herbicides DCMU, bentazon, amitrole, and SAN 6706 were tested for their ability to influence the carotenoid and pro-tochlorophyll(ide) composition as well as the protochloro-phyll(ide) phototransformation and the Shibata shift in dark-grown radish seedlings (Raphanus sativus L. cv. Saxa Treib). Bentazon enhanced the formation of lutein and carotenes, while SAN 6706 suppressed the biosynthesis of carotenoids. Amitrole led to a reduced accumulation of phototransformable pro-tochlorophyll(ide). The phototransformation of pro-tochlorophyll(ide) and the Shibata shift were not affected by any of the tested herbicides, irrespective of the presence or absence of activated phytochrome. From this we conclude that herbicides inhibiting photosystem II or producing chlorosis partly affect, but do not block, carotenoid and chlorophyll biosynthesis in dark-grown plants. The main herbicide effect becomes visible only after prolonged illumination.     

Comparing the Environmental Performance of Fluorescent Whitening Agents with Peroxide Bleaching of Mechanical Pulp

The use of fluorescent whitening agents (FWAs) instead of oxidative bleaching agents such as peroxide is an alternative for the bleaching of mechanical pulp. By this approach, the chromophores of the wood components in the pulp are not destroyed chemically but the brightness of the pulp is achieved by increased re-emission of blue light in the range of 400–500 nm. In this study, a typical FWA and peroxide bleaching chemicals are compared with respect to both production and application in the pulp mill. The life-cycle inventory shows that, on the one hand, the production of the FWA leads to higher releases of salts and adsorbable organically bound halogens (AOX) to surface waters and that, on the other hand, significantly less FWA is required in the application step in order to reach the same pulp brightness. The life-cycle impact assessment of the production step is presented in terms of Eco-indicator 95. These results, however, do not cover the environmental fate of various chemicals released to the aquatic environment in the course of the bleaching/whitening step. Therefore, this part is assessed by means of a more detailed investigation of the chemicals' environmental fate in rivers and their aquatic toxicity.     

In situ generation of hydrogen peroxide by carbohydrate oxidase and cellobiose dehydrogenase for bleaching purposes

The carbohydrate oxidase from Microdochium nivale (CAOX), heterologously expressed in Aspergillus oryzae, and cellobiose dehydrogenase from Myriococcum thermophilum (MtCDH), were assessed for their ability to generate bleaching species at a pH suitable for liquid detergents. The substrate specificities of CAOX and MtCDH were analyzed on a large variety of soluble and insoluble substrates, using oxygen as an electron receptor. Even insoluble substrates like cellulose were oxidized from both CAOX and MtCDH, but only MtCDH produced H₂O₂ on cotton as the sole substrate. To enhance the amount of cello-oligosaccharides formed from cotton as substrates for CAOX and MtCDH, various cellulases were used in combination with MtCDH or CAOX, leading to a 10-fold increase in H₂O₂. As model substrates for colored stains, the degradation of pure anthocyanins and stain removal of blueberry stains by CAOX and MtCDH was examined in the absence and presence of a horseradish peroxidase. Both enzymes were able to produce an amount of H₂O₂ sufficient to decolorize the pure anthocyanins within 2 h and showed significant cleaning benefits on the stains.     

PHOTOSYNTHESIS AND PRODUCTION OF HYDROGEN PEROXIDE BY SYMBIODINIUM (PYRRHOPHYTA) PHYLOTYPES WITH DIFFERENT THERMAL TOLERANCES1

Occurrences whereby cnidaria lose their symbiotic dinoflagellate microalgae (Symbiodinium spp.) are increasing in frequency and intensity. These so‐called bleaching events are most often related to an increase in water temperature, which is thought to limit certain Symbiodinium phylotypes from effectively dissipating absorbed excitation energy that is otherwise used for photochemistry. Here, we examined photosynthetic characteristics and hydrogen peroxide (H₂O₂) production, a possible signal involved in bleaching, from two Symbiodinium types (a thermally “tolerant” A1 and “sensitive” B1) representative of cnidaria–Symbiodinium symbioses of reef‐building Caribbean corals. Under steady‐state growth at 26°C, a higher efficiency of PSII photochemistry, rate of electron turnover, and rate of O₂ production were observed for type A1 than for B1. The two types responded very differently to a period of elevated temperature (32°C): type A1 increased light‐driven O₂ consumption but not the amount of H₂O₂ produced; in contrast, type B1 increased the amount of H₂O₂ produced without an increase in light‐driven O₂ consumption. Therefore, our results are consistent with previous suggestions that the thermal tolerance of Symbiodinium is related to adaptive constraints associated with photosynthesis and that sensitive phylotypes are more prone to H₂O₂ production. Understanding these adaptive differences in the genus Symbiodinium will be crucial if we are to interpret the response of symbiotic associations, including reef‐building corals, to environmental change.     

Novel pre-treatment processes to promote linen-containing fabrics properties

This study was undertaken to investigate the effect of plasma pre-treatment, followed by enzymatic treatment in the absence and presence of bleaching agent on the properties of linen and linen-containing fabrics. Different plasma gases (air, oxygen and nitrogen), enzymes (acid-cellulases, neutral-cellulase and alkaline-pectinase) as well as bleaching agents (peracetic acid and H₂O₂) were used. The changes in physico-mechanical properties, surface morphology and dyeing properties of the treated substrates have been investigated. The obtained results indicated that plasma pre-treatment followed by subsequent acid-cellulases/peracetic acid or alkaline-pectinase/H₂O₂ treatment result in: a dramatic improvement in hydrophilicity and wettability as well as in the degree of whiteness of the treated substrates, an improvement in reduction of surface roughness and extent of post-reactive dyeing, along with a weight loss and a drop in the tensile strength. The extent of surface modification as well as the changes in the above-mentioned properties are governed by the characteristics of the substrate, the plasma gas, the nature and dose of the used enzyme, as well as the type of bleaching agent and additive. The optimal treatment sequence for attaining better performance properties was O₂-plasma followed by alkaline-pectinase/H₂O₂ treatment in presence of PEG 400.     

蔗渣浆CEH漂白废水的毒性及毒性污染负荷的研究

采用发光细菌法对蔗渣浆CEH三段漂白废水进行了毒性研究 ,其中C段废水的毒性最大 ,其EC50 为 2 8.83% ,属于强毒级别 ;E段、H段废水的EC50 分别为 6 8.92 %、2 6 7.9% ,分别属于毒、无毒级别 ;其中C段的毒性排放负荷约占总废水毒性排放负荷的 6 7.5 %左右 ;结果表明 ,漂白废水的毒性排放负荷较大 ,约为 4 2 3.92 (TU·m3 吨浆 ) ,相当于 4 2 .93(gHgCl2 吨浆 ) ,对其治理不容忽视     

Global assessment of coral bleaching and required rates of adaptation under climate change

Elevated ocean temperatures can cause coral bleaching, the loss of colour from reef‐building corals because of a breakdown of the symbiosis with the dinoflagellate Symbiodinium. Recent studies have warned that global climate change could increase the frequency of coral bleaching and threaten the long‐term viability of coral reefs. These assertions are based on projecting the coarse output from atmosphere–ocean general circulation models (GCMs) to the local conditions around representative coral reefs. Here, we conduct the first comprehensive global assessment of coral bleaching under climate change by adapting the NOAA Coral Reef Watch bleaching prediction method to the output of a low‐ and high‐climate sensitivity GCM. First, we develop and test algorithms for predicting mass coral bleaching with GCM‐resolution sea surface temperatures for thousands of coral reefs, using a global coral reef map and 1985–2002 bleaching prediction data. We then use the algorithms to determine the frequency of coral bleaching and required thermal adaptation by corals and their endosymbionts under two different emissions scenarios. The results indicate that bleaching could become an annual or biannual event for the vast majority of the world's coral reefs in the next 30–50 years without an increase in thermal tolerance of 0.2–1.0°C per decade. The geographic variability in required thermal adaptation found in each model and emissions scenario suggests that coral reefs in some regions, like Micronesia and western Polynesia, may be particularly vulnerable to climate change. Advances in modelling and monitoring will refine the forecast for individual reefs, but this assessment concludes that the global prognosis is unlikely to change without an accelerated effort to stabilize atmospheric greenhouse gas concentrations.