Glucose cellulase

Cellulase The enzyme that cuts the linear chain of cellulose, a glucose polymer at 1-4-p-linkages into cellodextrins and glucose. 

Assays for endo-l,4- -glucanase [EC 3.2.1.4] (i.e., CMCase) and saccharifying cellulase (i.e., international filter paper U, IFPU) activities partially followed the methods recommended in the 1987 lUPAC report (65). When even undiluted enzyme samples fail to give the required glucose yield under prescribed assay conditions, the lUPAC committee recommends a less precise method. In the current study, cellulase activities in digester extracts were so low that the CMCU could only be defined as follows one CMC unit of activity was that amount of enzyme required to liberate one Hg glucose from CMC in 60 min. 

Analyses. Cellulase enzyme activities were determined as described earlier (21). Enzyme activities were expressed as international units (lU), i.e., mole glucose produced per minute. Cotton hydrolyzing activity was expressed as mg of glucose released in 24 hours per ml of enzyme. 

FP cellulase Glucose Cello- Xylose /3-glucosidase (g/1) biose (g/1) ratio (g/1) Arabi- nose (g/1) Total sugars Hydro- lysis (%)... 

Figure 4. Conversion of 50 g/L a-cellulose to glucose ly Genencor GC 123 cellulase supplemented to various ratios (r = pNPG U at 45°C/IFPU at 45 C) of free and immobilized -D-glucosidase. Nonsupplemented cellulase is included as a control Reactions were carried out in mixed tube with 10 mM sodium acetate pH 4.8 at 45°C.

RunUnococcus albus and Ruminococcus flavefadens. These bacteria are important cellulose-degraders found in the rumen of cattle and sheep (2). Most isolated strains ferment cellulose and xylan and all ferment cellobiose. Fermentation of glucose and some other carbohydrates depends on the particular strain. R flavefadens and B. succinogenes can ferment the highly ordered crystalline cellulosic su trates but R albus cannot. No evidence has been found for extracellular cellulase production by R albus, but Ohmiya et al. purified cellobiosidase from this culture 17). Laboratory growth of R albus has been conducted at pH 7.0 and 37 C. 

Langsford et al. reported that Cellulomonas fimi culture supernatants contained cellulase and proteinase activities, for which there appeared to be a relationship. Glucose repressed the synthesis of both activities and cellulose induced both 60), Adding cellulose to Cellulomonas sp. (NRCC 2406) cultures stimulated growth and improved production of cellulases 61). Optimum conditions for growth and cellulase production were pH 6.5 and 30 C. The addition of glucose in the presence of cellulose inhibited growth. Several species of Cellulomonas have cellobiose phosphorylase. 

Figure 2. Time course of cellulase activity accumulation in A. cellulofyticus cultures containing 15 g/L Solka Floe and various concentrations of glucose-l-phosphate.

The third group is that of compounds which may potentially be transported by the PTS and inhibit cAMP production. Cellulase synthesis is initiated after these compounds are consumed for cell growth. This group includes D-glucose, D-fructose, maltose, mannitol, glycerol, sorbitol, and -methyl glucoside. The presence of these compounds in Solka Floe fermentations, enhanced enzyme yields (132 to 254%) but the time required to complete cellulase synthesis took longer (106 to 148%) than the control. 

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