AFEX pretreatment and pelleting can have an effect on corn stover
cell morphology. Chundawat et al. (2011) reported that the
middle lamella and outer secondary cell wall were locations
affected by AFEX pretreatment and are areas enzymes can access
cell structures (Donohoe et al., 2009). Cell structure of AFEX-treated
corn stover had slight deformations evident in the micrographs
of the cell wall (Supplemental Fig. 1a and b). Micrographs of the
epidermis and underlying cell structure of AFEX-treated stover
indicated similar patterns (Supplemental Fig. 1c). Pelleting of
AFEX-treated corn stover caused severe disruptions of cell structure
apparent in the micrographs of the epidermis and underlying
cells of pelletized AFEX stover (Supplemental Fig. 1d). Similarly,
tracheary elements in untreated corn stover (Supplemental
Fig. 1e) had more remaining structure than in pelletized AFEX stover
(Supplemental Fig. 1f). In general, it was difficult to locate
remaining cell structures in pellets to image with SEM. Much of
the pellet appeared similar to SEM images of corn stover pellets
in Kaliyan and Morey (2010) and Ray et al. (2013).