Enzymatic cellulose

Environment Canada, 18 542 23 120 Enzymatic cellulose hydrolysis, 26 359 Enzymatic hydrolysis, 10 503, 535-536 Enzymatic methods, in sugar analysis, 23 475-476... 

A 72-h hydrolysis profile of a 10% acetic acid-pretreated softwood substrate (Fig. 1) represents a typical enzymatic cellulose hydrolysis course with the majority of the cellulose (up to 70%) broken down within the first 24 h. However, the conversion of the remaining cellulose ( 30%) was incomplete, even after another 2 d of incubation. The decrease in the hydrolysis rate in the latter phase is likely owing to accumulation of end products. To demonstrate that the end products played a major inhibitory role, we removed the produced sugar from the hydrolysate through ultrafiltration. Fresh buffer was then added to the retained protein and the residual substrate to attain the initial volume, and the hydrolysis was continued under the same condition. As shown in Fig. 1, significant increases in the hydrolysis rate were observed after the sugar removal at both 24 h and 48 h of incubation, with complete hydrolysis attained after 48 h and 60 h of incubation respectively. 

Gan Q, Allen SJ, and Taylor G. Design and operation of an integrated membrane reactor for enzymatic cellulose hydrolysis. Biochem Eng J, 2002 12(3) 223-229. 

Because free cellulose chain ends are so difficult to quantify, other measurable cellulose characteristics have been shown to be factors correlating to hydrolysis susceptibihty and rate [15,18]. These factors affect how well the cellulose-binding domain, CBD, adheres to the cellulose and how well the catalytic domain acts on the cellulose. Because of what can and cannot be measured easily, models of enzymatic cellulose hydrolysis combine adsorption behavior with kinetic action. 

Lee, S.H., Doherty, T.V., Linhardt, R.J., Dordick, J.S. Ionic liquid-mediated selective extraction of lignin from wood leading to enhanced enzymatic cellulose hydrolysis. Biotechnol. Bioengin 102(5), 1368-1376 (2009)... 

Huijgen WJJ, Smit AT, Reith JH, Uil Hd. (2011). Catalytic organosolv fractionation of willow wood and wheat straw as pretreatment for enzymatic cellulose hydrolysis. J Chem Technol Biotechnol, 86, 1428-1438. 

Gan Q, Allen SJ, Taylor G. (2005). Analysis of process integration and intensification of enzymatic cellulose hydrolysis in a membrane bioreactor. J Chem Techrwl Biotechnol, 80(6), 688-698. 

Hodge DB, Karim MN, Schell DJ, McMillan JD. (2009). Model-based fed-batch for high-solids enzymatic cellulose hydrolysis. Appl Biochem Biotechnol, 152(1), 88-107. 

Belafi-Bako, K., Koutinas, A., Nemestothy, N., Gubicza, L., Webb, C. (2006). Continuous enzymatic cellulose hydrolysis in a tubular membrane bioreactor. Enzyme and Microbial Technology, 38, 155—161. 

Increasingly, biochemical transformations are used to modify renewable resources into useful materials (see Microbial transformations). Fermentation (qv) to ethanol is the oldest of such conversions. Another example is the ceU-free enzyme catalyzed isomerization of glucose to fmctose for use as sweeteners (qv). The enzymatic hydrolysis of cellulose is a biochemical competitor for the acid catalyzed reaction. 

Enzymatic stone-washing is performed either entirely without stones or sometimes by a combination of stones and enzymes. CeUulases are used to attack the surface of the cellulose fiber, but leave the interior intact. Denim garments are dyed with indigo blue, which stays on the surface of the yam. The ceUulase partiy hydrolyzes the surface of the fiber, and the indigo blue is partiy removed. Either neutral-type ceUulases acting at pH 6—8 or acid-type ceUulases acting at pH 4—5 are used for these processes. 

Fermentation can be combined with other operations. For example, feedback inhibition of enzymatic hydrolysis of cellulose can be relieved by removal of the product glucose by fermentation as it forms. This is teni ed. simultaneou.s-saccharification-fermentation (SSF). 

Figure 1. Rate of the chemical (---) and enzymatic additions (—) of hydrocyanic acid to benzaldehyde (initial concentration 5 mM) in water/ethanol and in ethyl acetate/cellulose.

C. Oligo- and Poly-nucleotides.—The stepwise enzymatic synthesis of internucleotide bonds has been reviewed. A number of polynucleotides containing modified bases have been synthesised " in the past year from nucleoside triphosphates with the aid of a polymerase enzyme, and the enzymatic synthesis of oligodeoxyribonucleotides using terminal deoxynucleotidyl transferase has been studied. Primer-independent polynucleotide phosphorylase from Micrococcus luteus has been attached to cellulose after the latter has been activated with cyanogen bromide. The preparation of insolubilized enzyme has enabled large quantities of synthetic polynucleotides to be made. The soluble enzyme has been used to prepare various modified polycytidylic acids. ... 

The plant cell wall is a polymeric mesh consisting of cellulose, hemicellulose, pectin and protein. Cellulose and hemicellulose are integral components of the cell wall, but pectic substances are located mainly in the outer wall regions within the middle lamella (McNeil et ai, 1984). Pectic substances are more susceptible to enzymatic degradation, because they are more exposed than other cell wall components. Therefore, pectin-degrading enzymes may play a central role in the penetration of plant tissue by bacteria. 

Since many years, pectolytic enzymes have been widely used in industrial beverage processing to improve either the quality and the yields in fruit juice extraction or the characteristics of the final product [1,2]. To this purpose, complex enzymatic mixtures, containing several pectolytic enzymes and often also cellulose, hemicellulose and ligninolytic activities, are usually employed in the free form. The interactions among enzymes, substrates and other components of fruit juice make the system very difficult to be investigated and only few publications are devoted to the study of enzymatic pools [3-5], An effective alternative way to carry out the depectinisation process is represented by the use of immobilized enzymes. This approach allows for a facile and efficient enzymatic reaction control to be achieved. In fact, it is possible to avoid or at least to reduce the level of extraneous substances originating from the raw pectinases in the final product. In addition, continuous processes can be set up. 

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