Cellulase plant

Cellulases can also be eliminated fiom a mixture with xylanases by selective thermal inactivation. Cellulases are more thermolabile than xylanases in tiie cdlulolytic systems of the fungus Y-94 (79), T. harzianum 20), and Tkermoascus aurantiacus (77), but not in the Trickoderma reesei system (Biely, P. and Vrsanska, M., Slovak Academy of Sciences, Bratislava, unpublished results). Since cellulase thoixud inactivation causes a significant loss of xylanase also, a more convenient way to eliminate cellulase activity is by selective chemical or biological inhibition or inactivation. There appear, however, to be no reports on the existence of natural inhibitors that would be specific for cellulases. Such inhibitors of amylases and pectinases are known to occur in plants (27). 

Figure 7. Pilot plant process for cellulase production. Adapted from Ref. 20.

The second area of application involves the use of cellulase-free xylanases for removal of hemicellulose from pulps (10-20) and plant fibres (21). It is essential that these xylanase preparations are free of contaminating cellulase activity or damage to the cellulose fibres and consequently the product quality will result. 

A convenient procedure for assessing the digestibility of forages is the cellulase digestibility technique. This was refined by Jones and Hayward (1973) at the Welsh Plant Breeding Station (WPBS) in Aberystwyth (since 1992, the Institute for Grassland and Environmental Research). It was later extended to a two-stage procedure with a pepsin pre-treatment (Jones and Hayward, 1975). 

In the mid-1980s, my research group in Perth began a collaboration with a team of biochemists at La Trobe University in Melbourne to study the mechanism of action of a range of -glycan hydrolases and cellulases found in various plants and bacteria. The approach was to involve synthetic enzyme inhibitors. 

Xylanases act on the P-l,4-linked xylan, the most abundant of the hemicelluloses that constitutes over 30% of the dry weight of terrestrial plants.116 They resemble cellulases and cooperate with cellulases and xylosidases117 in digestion of plant cell walls.110116118-121 Galactanase digests the P-l,4-linked component of pectins.122... 

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