The breakdown of fibrils in MG after dilute acid hydrolysis
assisted by microwave can easily be observed. The dilute acid primarily
solubilizes and ruptures hemicellulose. Although acid
hydrolysis causes chemical changes in hemicellulose which disrupts
covalent bonds, hydrogen bonds, and van der Waals forces
(Li et al., 2010), the treatment allows cellulose and hemicellulose
to become more susceptible to enzymatic hydrolysis. In addition
to having a higher cellulose content than switchgrass (47% of cellulose
in MG, and 34% in switchgrass (Hu and Wen, 2008)), the
lower lignin content further ensures that MG would be a better
candidate for ethanol production. The presence of lignin localized
on the grass’ surface is less in MG than that in switchgrass. The
image of residual lignin condensing on the surface of the cellulose
confirms that acid treatment possesses only minimal effect on lignin
removal (Yu et al., 2011).