Enhanced enzymatic hydrolysis and ethanol production from cashew apple bagasse pretreated with alkaline hydrogen peroxide

• Conversion of cashew apple bagasse to fuel ethanol.
• The combination between different enzymes was evaluated during enzymatic hydrolysis.
• Cellulase and β-glucosidase showed the more effective interactions.
• The study demonstrates an insignificant impact of xylanase on the hydrolysis yield.
• The ethanol production by SHF and SSF processes showed promising using CAB-AHP.

The effect of combinations and ratios between different enzymes has been investigated in order to assess the optimal conditions for hydrolysis of cashew apple bagasse pretreated with alkaline hydrogen peroxide (the solids named CAB-AHP). The separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes were evaluated in the ethanol production. The enzymatic hydrolysis conducted with cellulase complex and β-glucosidase in a ratio of 0.61:0.39, enzyme loading of 30 FPU/gCAB-AHP and 66 CBU/gCAB-AHP, respectively, using 4% cellulose from CAB-AHP, turned out to be the most effective conditions, with glucose and xylose yields of 511.68 mg/gCAB-AHP and 237.8 mg/gCAB-AHP, respectively. Fermentation of the pure hydrolysate by Kluyveromyces marxianus ATCC 36907 led to an ethanol yield of 61.8 kg/tonCAB, corresponding to 15 g/L ethanol and productivity of 3.75 g/(L h). The ethanol production obtained for SSF process using K. marxianus ATCC 36907 was 18 g/L corresponding to 80% yield and 74.2 kg/tonCAB.

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