Mannanase cellobiohydrolase

Avicelase or Cellobiohydrolase + Mannanase. The treatment of spruce holocellulose first with avicelase or cellobiohydrolase and subsequently with mannanase effected an overall intensive degradation of... 

Figure 12. Cellobiohydrolase + mannanase treatment. Extensive degradation of tracheid wall material in all the layers. Scale = 1 fxm.

Harjunpaa, Vesa. Enzymes hydrolysing wood polysaccharides. A progress curve study of oligosaccharide hydrolysis by two cellobiohydrolases and three P-mannanases. 1998.76 p. + app. 11 p. 

Sprucewood holocellulose was treated with an endo-p-1,4-mannanase isolated from Aspergillus niger and an endo-/3-1,4-xylanase, two avicelases, and a cellobiohydrolase C isolated from Trichoderma viride. The mannanase hydrolyzed about a quarter of the mannan in 2-3 days without xylan or cellulose degradation. The xylanase hydrolyzed about half the xylan with 10% mannan solubilization. The three cellulases hydrolyzed up to 45% of the cellulose and 20% of the xylan, accompanied by 40-70% solubilization of the mannan. Combined xylanase-mannanase treatment hydrolyzed about half the xylan and mannan. Addition of mannanase to to cellulose-treated samples increased the degradation of the cellulose and mannan. Micromorphological studies of the variously treated specimens revealed a loss of substances in P/Slf T, and adjacent zones of S2 of the tracheid wall. 

Enzymes. The mannanase was isolated from Aspergillus niger (11) fraction 4 b was used throughout the experiments (cf. Table 1 in (11)). The xylanase 2, the avicelase 1, and the avicelase 2 were isolated from Trichoderma viride (10). The properties of these enzymes have also been described in the papers cited above. The cellobiohydrolase C was kindly supplied by Dr. R. D. Brown, Jr., and Dr. E. K. Gum, Jr. (Virginia Polytechnic Institute, Blacksburg). The isolation (from Trichoderma viride) and the properties of the cellobiohydrolase C are described in their 1974 paper (12). 

Avicelases or Cellobiohydrolase C - - Mannanase. The action of mannanase on delignified sprucewood holocelluloses that were treated with avicelase 1, avicelase 2, or cellobiohydrolase C for 48 hr gave similar degradation patterns. The rate of total degradation increased rapidly when the mannanase was added the rate was most pronounced in the case of avicelase 1 (Figure 4). 

Addition of mannanase resulted in high amounts of mannobiose and mannose. The amount of mannobiose relative to mannose was somewhat higher than in the case of the combined xylanase-mannanase treatment (Table II). The ratios of mannose. -galactose in the acid hydrolysates of the reaction solutions at the end of the experiment were 1 0.05 for the two avicelases and 1 0.03 for the cellobiohydrolase C. 

The properties of the enzymes used in this study have been described in former publications (10,11,15). Important for the following interpretation are their hydrolytic specificities. The xylanase did not hydrolyze either isolated mannans or celluloses—or only to a very small extent (10). The same is true for the mannanase with respect to xylans and celluloses (11,15). The avicelases, which were not purified to the same extent as the xylanase and mannanase, did not hydrolyze mannans, but they degraded xylans besides crystalline cellulose (10). Also, the highly purified cellobiohydrolase C (12) degraded xylan to some extent (Dr. E. K. Gum, Jr., personal communication). 

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