Elimination from xylanases

Elimination of Cellulases from Xylanases. Classical methods of protein fractionation can be used for to separate cellulases and xylanases on a large scale only when they differ considerably in molecular weight or isoelectric point. The Tricho-derma harzianum enzymes were separated by ultrafiltration because the xylanase was smaller and passed through the membrane into the ultrafiltrate 18). Fractional precipitation with organic solvents is another possibility (7). 

Cellulase-Negative Xylanase-Positive Mutants. There are two reports concerning the selection of such mutants from filamentous fungi, one on Pofyporus adm-tus (32) and the other cmi Trichoderma reesei (Durand, H. et al. Society CAYLA, Toulouse, France, unpublished results). An analysis of the eliminated cellulase genes has not been done, so it is not known if the mutants negative in endo(l- 4)-p-glucan-ase were deficient also in cellobiohydrolases. 

The use of filamentous fungi for production of xylanases was initially attractive because the enzymes are released extracellularly thus eliminating the need for cell lysis procedures. In addition, xylanase levels in fungal culture filtrates are typically in much higher concentrations than from yeasts and bacteria. Many examples of xylanases produced from fungi are listed in the review by Dekker (41). 

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