3. Desirable pretreatment process and process options
The purpose of pretreatment is to make lignocellulosic biomass
amenable to enzymatic reactions (saccharification) with reasonable
processing cost. Some commonly observed outcomes of pretreatment
include decrease of lignin content, increase of surface
area, and decrease of crystallinity of the biomass; all of which
result in enhanced enzymatic hydrolysis rate and yield (Kim
et al., 2003; Kim, 2013). Pretreatment is an essential element in
the biorefining of lignocellulosic substrates. Kim (2013) described
that pretreatment plays a major role in the economics of the overall
bioconversion process because all of the subsequent processes
(enzymatic saccharification, fermentation, and the downstream
processes) are tailored to the pretreatment results. Ideally, a pretreatment
process should (1) improve the enzymatic hydrolysis
reaction, (2) produce minimal/no inhibitory compounds, and (3)
require reasonable capital and operating costs (with low energy
input and minimal waste) (Drapcho et al., 2008; Kim, 2013).