Alkaline pretreatment and response surface methodology based recombinant enzymatic saccharification and fermentation of sugarcane tops

In present study, the water-soluble extractives removal prior to alkali pretreatment of sugarcane tops (SCT) was carried out. The solid alkali pretreated SCT (apSCT) recovered on Field-emission scanning electron microscopy (FE-SEM) analysis showed exposure of cellulosic fibres as compared with raw SCT. The analyses of apSCT by Fourier Transform Infrared (FT-IR) Spectroscopy, X-ray diffraction (XRD) and High performance liquid chromatography (HPLC) analysis also confirmed the enhanced cellulose content in apSCT. Optimum conditions for response surface methodology based saccharification of apSCT at 40 degrees C, 150 rpm were 2.14% (w/v) apSCT loading in citrate-phosphate buffer (50 mM, pH 6.0), recombinant hydrolytic enzymes (from Clostridium/Hungateiclostridium thermocellum) loading for endo-1,4-beta-glucanase (CtCel8A) = 213.2 U/g, cellobiohydrolase (CtCBH5A) = 272.5 U/g and beta-glucosidase (HtBg1) = 299.8 U/g for 49.2 h. Under optimized saccharification conditions, the total reducing sugar yield was 265 mg/g (glucose 214 mg/g) of apSCT. Fermentation of produced glucose by S. cerevisiae gave 0.19 g/g glucose of bioethanol.

Automated summary

The study found that the removal of water-soluble extractives prior to alkali pretreatment can increase the cellulose content in SCT, and optimized conditions for enzymatic saccharification were determined to convert it into glucose and bioethanol. Fermentation of the produced glucose by S. cerevisiae yielded bioethanol.