2. Scanning electron microscopic (SEM)
The acid and alkali pretreated biomass samples were subjected to microscopic study. The residue
remaining after enzymatic saccharification was also selected for microscopic observation. The sample from each
pretreatment was filtered and washed using hot water prior to drying at 80°C for 24 h. The dried sample was
subjected to SEM using a Hitachi S-3400N model with Energy-dispersive X-ray spectroscopy (Horiba EMAX
EDX) (SEM-EDX) under backscattered electrons (BSE) mode with 15 kV.
3. Products quantification
Sugars and ethanol concentrations were analysed using high performance liquid chromatography (HPLC)
(Waters 2707). Sugar Pack™1 column was used for the analysis. Samples were filtered through 0.45 μm PTFE
membrane filters and injected to the column. The deionized water was used as the mobile phase with flow rate
of 0.5 ml min-1. The column temperature was maintained at 75°C.
The ethanol yield (g g-1) was calculated based on experimental ethanol produced and expressed as g
ethanol per total g of sugar utilised (Eq. 1) and the fermentation efficiency or theoretical ethanol yield (%) was
calculated based on the ratio of ethanol yield obtained against theoretical maximum ethanol yield (Eq. 2). The
ethanol productivity was calculated based on ethanol produced against fermentation time (Eq. 3)