TEM micrographs display variable degrees of delamination and nanofibrillation within biomass cell walls (arrows). a) Control, (b) ZC, (c) SG, and (d) HS. The level of delamination and nanofibrillation seen in the SG and HS reactor samples indicate a substantial increase in accessibility (c’,d’). The SG and HS reactor samples also show cell wall fragmentation (c,d). Bars = 5 μm (a,b,c,d) and 0.5 μm (a’,b’,c’,d’). HS, horizontal screw; SG, steam gun; TEM, transmission electron microscopy; ZC, ZipperClave®.