3. Results and discussion
3.1. Pretreatment of CS
In this study, the dilute NaOH extraction (AE), Fenton pretreatment
(FT), sequential dilute NaOH extraction and Fenton pretreatment
(AE-FT), and sequential Fenton pretreatment and dilute
NaOH extraction (FT-AE) were employed for pretreating CS, and
the effects of cellulose structural changes in the CS were investigated.
As presented in Fig. S1 (in Supplementary materials), a compositional
analysis of CS pretreated using the Fenton reagent for
30 min revealed that the amounts of hemicellulose could be
slightly reduced and lignin was significantly removed.
Additionally, dilute NaOH extraction for 1 h could be effectively
removed lignin. After the pretreatment combined Fenton pretreatment
and dilute NaOH extraction (AE-FT and FT-AE), both lignin
and hemicellulose were reduced significantly. Removal of lignin
by NaOH is important, since the NaOH would then serve to also
remove a component that otherwise adsorbs or inhibit cellulase
(Kim et al., 2015; Ko et al., 2015a), thereby increasing the amount
of enzyme required (Ko et al., 2015b). Notably, the FT-AE pretreatment
resulted in the higher ratio of glucan/xylan than AE-FT pretreatment
did, and FT-AE-CS had higher content of cellulose and
lower content of lignin than AE-FT-CS.