Synergistic actions of exo-type cellulases in the hydrolysis of cellulose with different crystallinities

Hoshino, Eiichi; Shiroishi, Masahiro; Amano, Yoshihiko; Nomura, Masafumi; Kanda, Takahisa

doi:10.1016/s0922-338x(97)89248-3

Cited by 64 publications

(41 citation statements)

References 25 publications

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“…Higher endo-exo synergy has been reported for substrates that have been treated to reduce CrI, for example, homogenized Avicel vs. Avicel (Henrissat et al, 1985) and ball-milled Solka Floc vs. Solka Floc (Fan et al, 1981). However, Hoshino et al (1997) observed higher DS as CrI increased. As noted previously in our discussion of CrI, it is difficult to attribute observed changes to CrI based on work involving treatments that also change accessible surface area.…”

Section: Synergismmentioning

confidence: 91%

“…The DP of wood after pulping is reduced to 500 -1,500 (Bertrain and Dale, 1985;Klein and Snodgrass, 1993;Swatloski et al, 2002). After partial acid hydrolysis, the DP of Avicel is further decreased to 130 -800 (Hoshino et al, 1997;Ng and Zeikus, 1980;Ross-Murphy, 1985;Steiner et al, 1988;Wood, 1985), depending on hydrolysis conditions (Dong et al, 1998) and the DP of the original substrate (Wood, 1988). Similarly, the DP of natural cotton can be as high as 15,000, but is reduced to 1,000 -3,000 or less in the preparation of cotton linters involving treatment to accomplish dewaxing and whitening (Kleman-Leyer et al, 1992Okazaki and MooYoung, 1978;Ryu and Lee, 1982), and filter paper made from cotton pulp has a DP of 500 -1,000 or higher (Nisizawa, 1973;Kongruang et al, 2004).…”

Section: Degree Of Polymerizationmentioning

confidence: 99%

“…Cotton (Hoshino et al, 1997;Sinitsyn et al, 1991), bacterial cellulose from Aacetobacter xylinum (Boisset et al, 1999;Gilkes et al, 1992;Valjamae et al, 1999), and cellulose from the alga Valonia ventricosa (Boisset et al, 1999;Fierobe et al, 2002) provide examples of highly crystalline cellulose, while phosphoric acid swollen cellulose and ball-milled cellulose are regarded as amorphous cellulose (Hoshino et al, 1997; (Mosier et al, 1999). c: Organization of lignocellulose origanization into elementary fibrils and microfibrils (Klein andSnodgrass, 1993).…”

Section: Crystallinity Index (Cri)mentioning

confidence: 99%

“…Bacterial cellulose (BC) has an average DP of 2,000 -3,000 (Hestrin, 1963;Fierobe et al, 2002;Valjamae et al, 1999), while bacterial microcrystalline cellulose (BMCC) prepared by treatment of BC with acids ranges from 130 -1,300, depending on hydrolysis conditions (Valjamae et al, 1999). The DP of phosphoric-acid swollen cellulose (PASC) ranges from 30 to more than 1,000 Krassig, 1985;Petre et al, 1981;Wood and McCrae, 1972), depending on the DP of the starting substrate (Wood, 1988;Hoshino et al, 1997), as well as the phosphoric acid incubation time and temperature (Krassig, 1993).…”

Section: Degree Of Polymerizationmentioning

confidence: 99%

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Toward an aggregated understanding of enzymatic hydrolysis of cellulose: Noncomplexed cellulase systems

Zhang

Lynd

2004

Biotech & Bioengineering

1,658

1,284

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Information pertaining to enzymatic hydrolysis of cellulose by noncomplexed cellulase enzyme systems is reviewed with a particular emphasis on development of aggregated understanding incorporating substrate features in addition to concentration and multiple cellulase components. Topics considered include properties of cellulose, adsorption, cellulose hydrolysis, and quantitative models. A classification scheme is proposed for quantitative models for enzymatic hydrolysis of cellulose based on the number of solubilizing activities and substrate state variables included. We suggest that it is timely to revisit and reinvigorate functional modeling of cellulose hydrolysis, and that this would be highly beneficial if not necessary in order to bring to bear the large volume of information available on cellulase components on the primary applications that motivate interest in the subject. B

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Section: Synergismmentioning

confidence: 91%

Section: Degree Of Polymerizationmentioning

confidence: 99%

Section: Crystallinity Index (Cri)mentioning

confidence: 99%

Section: Degree Of Polymerizationmentioning

confidence: 99%

See 2 more Smart Citations

Toward an aggregated understanding of enzymatic hydrolysis of cellulose: Noncomplexed cellulase systems

Zhang

Lynd

2004

Biotech & Bioengineering

1,658

1,284

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“…This synergy has been confirmed since then with fungal as well as bacterial CBH (3,21,25,33,35,43,52). Several explanations have been tentatively proposed to account for the cooperation between two "exocellulases."…”

mentioning

confidence: 81%

Imaging the Enzymatic Digestion of Bacterial Cellulose Ribbons Reveals the Endo Character of the Cellobiohydrolase Cel6A fromHumicola insolensand Its Mode of Synergy with Cellobiohydrolase Cel7A

Boisset

Fraschini

Schülein

et al. 2000

Appl Environ Microbiol

201

163

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Dispersed cellulose ribbons from bacterial cellulose were subjected to digestion with cloned Cel7A (cellobiohydrolase [CBH] I) and Cel6A (CBH II) from Humicola insolens either alone or in a mixture and in the presence of an excess of ␤-glucosidase. Both Cel7A and Cel6A were effective in partially converting the ribbons into soluble sugars, Cel7A being more active than Cel6A. In combination, these enzymes showed substantial synergy culminating with a molar ratio of approximately two-thirds Cel6A and one-third Cel7A. Ultrastructural transmission electron microscopy (TEM) observations indicated that Cel7A induced a thinning of the cellulose ribbons, whereas Cel6A cut the ribbons into shorter elements, indicating an endo type of action. These observations, together with the examination of the digestion kinetics, indicate that Cel6A can be classified as an endo-processive enzyme, whereas Cel7A is essentially a processive enzyme. Thus, the synergy resulting from the mixing of Cel6A and Cel7A can be explained by the partial endo character of Cel6A. A preparation of bacterial cellulose ribbons appears to be an appropriate substrate, superior to Valonia or bacterial cellulose microcrystals, to visualize directly by TEM the endo-processivity of an enzyme such as Cel6A.Despite a large number of studies, the mechanism of the enzymatic digestion of crystalline cellulose stands as a major unsolved problem of persisting industrial and scientific significance. As early as 1950, it was realized that the degradation of cellulose required a complex of enzymes working together (36). This crucial observation has been confirmed by an extensive number of studies. Following these reports, a general picture has emerged indicating that at least three types of enzymes need to cooperate to digest efficiently crystalline cellulose into glucose: (i) endoglucanases (EC 3.2.1.4), which cut the cellulose chains randomly; (ii) cellobiohydrolases (CBH) (EC 3.2.1.91), which recurrently cleave cellobiose from the cellulose chain ends; and (iii) ␤-glucosidases (EC 3.2.2.21), which hydrolyze cellobiose and various soluble cellodextrins into glucose (reviewed in references 4, 15, 16, 22, 30, 42, 44, and 53).The complementary activities of the different enzymes is thought to be responsible for synergistic effects, whereby the enzymatic activity of a mixture of two or several enzymes is substantially higher than the sum of the activities of the individual enzymes. Several types of synergy have been described, the easier to apprehend being the cooperation action of endoand exo-acting enzymes on cellulose (21,28,35,49,50). In such a cooperation, the action of endocellulases is to increase the number of chain ends and, therefore, to enhance the action of exocellulases, which themselves appear to be the key enzymes for the digestion of crystalline cellulose. In this context, one of the main characteristics of CBH is that they act on cellulose chains in a "processive" manner (10,23,27,37,38,45), as they progress along the polymer chain while releasing cello...

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Optimized mixtures of recombinant Humicola insolens cellulases for the biodegradation of crystalline cellulose

Boisset

Petrequin

Chanzy

et al. 2000

Biotech & Bioengineering

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The digestion of bacterial cellulose ribbons by ternary mixtures of enzymes consisting of recombinant cellulases (two cellobiohydrolases, Cel6A and Cel7A, and the endoglucanase Cel45A) from Humicola insolens was investigated over a wide range of mixture composition. The extent of digestion was followed by soluble sugar release (saccharification) analysis together with transmission electron microscopy (TEM) observations. It was found that the addition of minute quantities of Cel45A induced a spectacular increase in saccharification of the substrate with either Cel7A or the mixture of Cel6A and Cel7A. Conversely, only a moderate saccharification resulted from the mixing of Cel45A and Cel6A. This difference is believed to originate from (1) the occasional endo character of Cel6A and (2) the competition of Cel6A and Cel45A for the substrate sites that are sensitive to endo activity. Interestingly, the mixture of enzymes giving rise to the highest saccharification rate did not always correspond to mixtures of enzymes generating the highest synergy. TEM images revealed that the bacterial cellulose ribbons became at the same time cut and narrowed down under the action of an optimized mixture of the three enzymes. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 72: 339–345, 2001.

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Synergistic actions of exo-type cellulases in the hydrolysis of cellulose with different crystallinities

Cited by 64 publications

References 25 publications

Toward an aggregated understanding of enzymatic hydrolysis of cellulose: Noncomplexed cellulase systems

Toward an aggregated understanding of enzymatic hydrolysis of cellulose: Noncomplexed cellulase systems

Imaging the Enzymatic Digestion of Bacterial Cellulose Ribbons Reveals the Endo Character of the Cellobiohydrolase Cel6A fromHumicola insolensand Its Mode of Synergy with Cellobiohydrolase Cel7A

Optimized mixtures of recombinant Humicola insolens cellulases for the biodegradation of crystalline cellulose

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