Simultaneous production of cellulase and reducing sugar from alkali-pretreated sugarcane bagasse via solid state fermentation

Abstract

This study optimized alkali pretreatment of sugarcane bagasse (SCB) and investigated the potential of alkali-pretreated SCB in producing cellulase and reducing sugar by a white-rot fungus, P. sanguineus, via solid state fermentation (SSF). The fermentability of the reducing sugar produced during SSF was examined by co-culturing yeast, Saccharomyces cerevisiae, with P. sanguineus. Central composite design (CCD) was applied to optimize the pretreatment based on reducing sugar yield obtained from enzymatic hydrolysis of the pretreated SCB. The model developed from CCD fitted the data well, and the optimized conditions for alkali pretreatment were 128 °C, 0.62 M NaOH, and 30 min with a reducing sugar yield of 97.8%. The alkali-pretreated SCB after washing and drying was cultivated with P. sanguineus during SSF. It was found that cellulase and reducing sugar can be produced simultaneously from this SSF system. The maximum cellulase activities determined from filter paper assay (FPase), carboxylmethylcellulase (CMCase) assay and β-glucosidase assay were 0.02 IU/mL, 0.11 IU/mL, and 0.13 IU/mL on day 8, day 3, and day 6 of cultivation, respectively. The maximum reducing sugar concentration of 19.9 mg/g pretreated SCB was obtained on day 4 of SSF. The reducing sugar produced was converted into ethanol upon the addition of yeast into the SSF system. Evidently, the reducing sugar acquired can be further utilized to produce other valuable products in subsequent processes.

Keywords

• Pretreatment
• Sugarcane bagasse
• Central composite design
• Cellulase
• Reducing sugar
• Solid state fermentation