Simultaneous saccharification and fermentation and a consolidated bioprocessing for Hinoki cypress and Eucalyptus after fibrillation by steam and subsequent wet-disk milling

An advanced pretreatment method that combines steam treatment (ST) with wet disk milling (WDM) was evaluated using two different species of woods, viz., Hinoki cypress (softwood) and Eucalyptus (hardwood). Bioconversion of the pretreated products was performed using enzymatic saccharification via a commercial cellulase mixture and two types of fermentation processing, i.e., yeast-based simultaneous saccharification and fermentation (SSF) and Clostridium thermocellum-based consolidated bioprocessing (CBP). A higher yield of glucose was obtained in the enzymatic saccharification and fermentation products from SSF and CBP with pretreatment consisting of WDM after ST, as compared to either ST or WDM alone. Maximum ethanol production via SSF and CBP were 359.3 and 79.4 mg/g-cellulose from Hinoki cypress, and 299.5 and 73.1 mg/g-cellulose from Eucalyptus, respectively. While the main fermentation product generated in CBP was acetate, the total products yield was 319.9 and 262.0 mg/g-cellulose from Hinoki cypress and Eucalyptus, respectively.