Enzymatic Bleaching

11 Mixed Enzymatic Process in Scouring of Cotton Fabrics 

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According to our preliminary calculations on the feasibility of the enzymatic bleaching process, the economically acceptable amount of enzyme should not exceed 10 lU/g of pulp. Thus, realization of these applications may currently be confounded by economic feasibility, although improvements in the technologies involved in enzyme production and utilization are to be expected. 

Oxidoreductases Glucose oxidase Aspergillus niger Increase gluten strength Improve shelf life Preserve milk Indirect enzymatic bleaching Tooth paste... 

A Kantelinen, B Hording, J Sundquist, M Linko, L Viikari. Proposed mechanism of the enzymatic bleaching of kraft pulp with xylanases. Holzforschung 47 318-324, 1993. 

Enzymatic Bleached kraft pulp defibrillation Enzymatic pre-treatment by fungus OS 1 (isolated and 200-250 nm in length PALE having 5-60 nm in diameter and 200-300 nm in length 10-250 nm in width, the majority is... 

Buschle-Diller G, Yang X D, Yamamoto R (2001), Enzymatic bleaching of cotton fabric with glucose oxidase . Text. Res. J., 71(5), 388-394. 

Lipoxygenase catalysed processes. Enzymatic bleaching of wheat flour by lipoxygenases is a widely practised operation in Europe and North America. The process is due to co-oxidation of carotenoids during oxygenation of polyunsaturated fatty acids such as linoleic acid to hydro-peroxy-octadecadienoic acid (Hildebrand and Hymowitz, 1982 Nicolas et al., 1982). The hydro-peroxy-octadecadienoic acids (HCDs) are key intermediary compounds for the synthesis of other important... 

Bleaching is reversed in the dark and the red-purple color of rhodopsin returns. This is thought to occur by the reduction of all-Pms-retinal to vitamin Ai (retinal), which diffuses from the rod into the pigment epithelium, where it is converted enzymatically to the 1 l-c isomer of vitamin At. The enzymatic isomerization is followed by diffusion back into the rod, oxidation to 11 -rfr-retinal, and combination with opsin to form rhodopsin. This process is shown schematically in Figure 12.5.[Pg.289]

Modified starch Substance obtained by one or more chemical treatments of edible starches, which may have undergone a physical or enzymatic treatment, and may be acid or alkali thinned or bleached... 

Attempts to remove hemicellulose for production of dissolving pulps with very low hemicellulose contents have shown that complete enzymatic hydrolysis of hemicellulose within the pulp is difficult to achieve. The xylan content in delignified mechanical aspen pulp was reduced from approximately 20 to 10%, whereas in bleached hardwood sulphite pulp the xylan content was decreased from 4 to only 3.5% even at very high enzyme dosages (50). The complete removal of residual hemicellulose seems thus unattainable, apparently due to modification of the substrate or to structural barriers. 

The following gives a brief compilation of procedures to determine hexenuronic acids in cellulosic pulp samples. The common methods are based on hydrolysis of HexA moieties from pulp, either enzymatically or chemically, with subsequent quantification of the hydrolysis products either directly or after chemical conversion into UV active compounds. A comparison of these three methods is given by Tenkanen et al. [136]. For comparison rather than exact determination of HexA, e.g., during bleaching stages, the diffuse reflection UV VIS method can be applied [137]. A photoacoustic FTIR procedure based on chemometric analysis has been described as well [138]. In Table 3, the available methods to analyze HexA moieties in cellulosic material are summarized. 

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