86. White, A. R. and R. M. Brown, Jr. 1981.
Enzymatic hydrolysis of cellulose: visual characterization of
the process. Proc. Nat. Acad. Sci. U.S.A. 78:1047-1051.
86. Abstract
Cellulose from the Gram-negative bacterium
Acetobacter xylinum has been used as a model substrate
for visualizing the action of cellulase enzymes from the fungus
Trichoderma reesei. High-resolution electron microscopy
reveals that A. xylinum normally produces a ribbon of cellulose
that is a composite of bundles of crystalline microfibrils. Visual
patterns of the process of cellulose degradation have been established.
Enzymes are initially observed bound to the cellulose ribbon.
Within 10 min, the ribbon is split along its long axis into bundles
of microfibrils which are subsequently thinned until they are
completely dissolved within 30 min. Incubations with purified
components of the cellulase enzyme system produced less dramatic
changes in ribbon structure. Purified 1,4--D-glucan cellobiohydrolase
I (D) (EC 3.2.1.91) produced no visible change in cellulose structure.
Purified endo-1,4--D-glucanase IV (EC 3.2.1.4) produced some
splaying of ribbons into microfibril bundles. In both cases,
whole ribbons were present even after 60 min of incubation, visually
confirming the synergistic mode of action of these enzymes.