Pretreatment of cashew apple bagasse using protic ionic liquids: Enhanced enzymatic hydrolysis

- Synthesis and characterization of the protic ionic liquid 2-HEAA.
- Different pretreatments using 2-HEAA was studied over cashew apple bagasse.
- 2-HEAA removed lignin from untreated cashew apple bagasse.
- IL-pretreated cashew apple bagasse exhibited higher cellulose crystallinity.
- Enzymatic hydrolysis from CAB pretreated with IL produce a high sugar yield.

To enhance the enzymatic digestibility of cashew apple bagasse (CAB) feedstock in order to produce sugar fermentation-derived bioproducts, the CAB was subjected to three different pretreatments with the ionic liquid 2-hydroxyl-ethylammonium acetate (2-HEAA) and characterized by FTIR, NMR and chemical methods. All conditions were able to delignify CAB, however the best lignin removal (95.8%) was achieved through the method performed with 8.7% w/w of CAB/2-HEAA ratio at 130 °C for 24 h. Although the cellulose crystallinity has been increased in CAB treated with the ionic liquid, but this fact did not influence its digestibility. Nevertheless, the pretreatment with 2-HEAA enhanced significantly the cellulose digestibility, increasing the glucose yield from 48 to 747.72 mgglucose/gCAB. Furthermore, 2-HEAA pretreatment was efficient even with reused ionic liquid, obtaining high glucose concentration.