Study of enzymatic digestion of cellulose by small angle neutron scattering.

Small angle neutron scattering (SANS) was used to study the structure of Avicel (FD100) microcrystalline cellulose during enzymatic digestion. Digestions were performed in either of two modes: a static, quiescent mode or a dynamic mode using a stirred suspension recycled through a flow cell. The scattering pattern for as-received Avicel in D2O buffer is comprised of a low Q power law region resulting from the surface fractal character of the microcrystalline fibers and a high Q roll-off due to scattering from water-filled nanopores with radii ∼20 A. For digestions in the dynamic mode the high Q roll-off decreased in magnitude within ∼1 h after addition of enzymes, whereas in the static digestions no change was observed in the high Q roll-off, even after 60 h. These results indicate that only with significant agitation does enzyme digestion affect the structure of the nanopores.