Bleaches optimization

Further research directed toward optimizing bleach sequences, as well as development of biotechnologies to produce other enzymes that can directly delignify pulps with high specificity of action, can be expected. 

Even if the fatty acid esters have been sulfonated under optimal conditions the ester sulfonates are dark-colored [12,33] so the sulfonated product has to be bleached. The second pretreatment is the neutralization of the acid product to obtain the salt of the a-sulfo fatty acid ester. Different techniques have been published in the literature. Kapur et al. suggested bleaching with 3-4 wt % NaOCl (15 wt % solution) after neutralization with a 30% aqueous solution of sodium hydroxide. This technique is for small-scale sulfonation [46]. 

In an optimally controlled process free from transition-metal ions hydrogen peroxide bleaching is remarkably safe, there being no reported detrimental effects of bleaching at around 100 °C or for more than several hours [143]. Under such conditions, most of the peroxide appears to be consumed in the oxidation of chain end units of the cellulose macromolecule. The other major effect on the substrate is oxidation of secondary hydroxy to keto groups, accompanied by the formation of very few aldehyde or carboxyl groups [235]. 

A bright cyan-green fluorescent protein was isolated from Clavu-laria coral [86]. Since one of the intermediates displayed fast bleaching, a screen for more photostable variants was performed. The optimized monomeric variant was named teal fluorescent protein 1 (mTFPl). It has an excitation and emission maximum at 462 and 492 nm, respectively, so this protein is spectrally located in between CFP and GFP. With an extinction coefficient of 64,000 M 1 cm-1 and a quantum yield of 0.85 mTFPl is a very bright fluorescent protein. 

Coral bleaching and decrease in spatial extent of optimal coral habitat. 

The important parameters in bleaching wood pulp are the concentration (consistency) of pulp and bleaching chemicals, the reaction temperature and duration (residence time), the mixing of pulp and chemical, and the pH at which the reactions are carried out. Initial temperatures and concentrations are usually selected based upon experience with a particular pulps needs. Control is achieved by carefully balancing all these various factors to optimize bleaching with a minimum expenditure of chemical. 

After conversion to the proper DE, the reaction is stopped in the neutralizer tank by raising the pH with soda ash (sodium carbonate) to 4.5-5.0. This pH is critical not only to optimize the conditions under which the proteins and fats can be removed, but also to reduce the risk of unnecessary color development. At this point, the liquor may be pumped to an enzyme tank for further enzyme-catalyzed conversion, or clarified, bleached and evaporated. 

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