Hemicellulases and cellulases

The baking quality of rye flour and the shelf life of rye bread can be improved by partial hydrolysis of the rye pentosans. Technical pentosanase preparations are mixtures of P-glycosidases (1,3-and 1,4-P-D-xylanases, etc.). 

Glycosidases (cellulases and amylases from As-pergillus niger) in combination with proteinases are recommended for removal of shells from shrimp. The shells are loosened and then washed off in a stream of water. 

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The cambium was isolated firom spruce (Picea abies) logs felled in October-November. The bark was stripped off, and the cambium was removed by gentle scraping. The isolated cambium was immediately fiozen in liquid nitrogen and fi-eeze-dried. The carbohydrate composition of the isolated cambium was analysed by HPLC after enzymatic hydrolysis using Pectinex Ultra and a mixture of cellulases and hemicellulases (Buchert et al 1993). 

Water removal on the paper machine has been shown to improve as a result of limited hydrolysis of the fibres in recycled paper. Mixtures of cellulases and hemicellulases were found to decrease the SR-value, which describes the drainage behaviour of the fibres (45), The effect is apparently due to fibrillation or change in the composition of fine particles. 

Potato pulp and potato pulp residue (after acidic treatment) and nutrient salt solution and potato protein liquor, respectively, were used for the production of cellulases and hemicellulases by Trichoderma reesei Rut C30 in a continuously operated bioreactor, (Klingspohn and Schiigerl... 

Besides his fundamental research in the carbohydrate field, the functions of Courtois as the head of a hospital laboratory for many years led him to publish a number of papers dealing with clinical chemistry, among which may be cited determination of ethyl alcohol, proteins, acidic phosphatases, and trehalase in blood determination of the basic groups of proteins by phytic acid study of the phytosoluble glycoproteins in biological fluids and identification and determination of scyllitol in urine. Under the aegis of the International Pharmaceutical Federation, he participated in the standardization of the methods proposed for the assay of such enzymes as cellulases and hemicellulases. 

All steps of the process need to undergo major efficiency improvements. The cost of enzymes, for example, needs to fall by 90 percent from its 2003 level. This might sound unrealistic, but it is not unusual to increase the effectiveness of enzyme production by factors of ten, 100, or even 1000. By modifying the amino acid sequences of the cellulase and hemicellulase enzymes, biochemists from Genencor and Novozymes have been able to make them dramatically more effective, and recent advances suggest that the cost target for the enzymes will be exceeded in due course. 

A commercial fractionation process in which groats are dry-milled and the comminuted groats are soaked in a solution of cellulases and hemicellulases has been developed.9 In addition to the starch the process produces fiber and protein fractions. Unlike wheat starch, oat starch cannot be separated from the grain by selective hydration and centrifugation, because of hydrated bran and protein layers. 

The complex nature and interconnectivity of plant cell wall polymers preclude straightforward enzymatic digestion. There are dozens of enzyme families involved in plant cell wall hydrolysis, including cellulases, hemicellu-lases, pectinases, and lignin-modifying enzymes. The Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (IUBMB) has classified cellulases and hemicellulases, like all enzymes, into different classes based on activity. Table 33.2 and Table 33.3, compiled from the IUBMB enzyme nomenclature database (http //www.chem.qmul.ac.uk/iubmb/ enzyme/), list the IUBMB enzyme classifications for cellulases and hemicellulases.153... 

Biochemical conversion processes Enz)unes and micro-organisms are frequently used as biocatalysts to convert biomass or biomass-derived compounds into desirable products. Cellulase and hemicellulase enzymes break down the carbohydrate fractions of biomass into five-and six-carbon sugars, a process known as hydrolysis. Yeast and bacteria ferment the sugars into products such as ethanol. Biotechnology advances are expected to lead to dramatic biochemical conversion improvements. 

Aspergillus species especially A. oryzae, are the source of cellulases and hemicellulases... 

As with the amylases, such other enzymes as dextranases, cellulases, and hemicellulases can be used to study oligosaccharides whose structure is closely related to the relevant polysaccharide. The particular value of these enzymes is that their specificity depends on the position of substitution of the glycosidic links as well as on their configuration. 

Pectinases, cellulases and hemicellulases are used for clarification of fruit juices, juice extraction, improvement of cloud stability of vegetable and fruit juices and nectars, liquefaction and maceration of fruits and vegetables, reduction of cooking time of pulses and improvement of rehydration characteristics of dried vegetables. The chemical basis of these treatments and of the consequential changes in sensory and nutritional quality are discussed. 

The commercial liquefaction enzyme typically used (Rhoapect 7016) contained predominantly cellulase and hemicellulase activity but with some pectinase activity. The use of more pectinase and less liquefaction enzyme represented a more favorable treatment economically and was actually more effective in reducing viscosity (Table II). Also, as predicted, the steady state flux of the membranes was higher when pectinase predominated. 

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