Enhancing enzymatic hydrolysis of green coconut fiber—Pretreatment assisted by tween 80 and water effect on the post-washing

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This study evaluated the hydrothermal, alkaline (NaOH) and acid (H2SO4) pretreatment all combined with Tween 80 of the green coconut fiber aiming to improve the fermentable sugars production during the enzymatic hydrolysis. In addition, the water use during the post-washing of the pretreated materials was also assayed, seeking to ration its use without compromising the enzymatic hydrolysis and the removal of inhibitors. Untreated and pretreated biomass were assayed in terms of total solids, extractables, polysaccharides, lignin and total ashes according to the protocols proposed by NREL. Enzymatic hydrolysis was carried out using the preparation of cellulases from Trichoderma reesei ATCC 26921 and β-glucosidases (NS-22118 DCN00218) and xylanases (NS-22036 CDN01015). Additionally, the mass loss during pretreatment and washing was estimated. Results showed that the use of 3.0% (w/w) Tween 80 in the dilute alkaline pretreatment (2.0% (w/v) NaOH, 121 °C, 10 min) increased the conversion into glucose during the enzymatic hydrolysis of the pretreated materials from 48.7% to 56.1%. However, it did not show any influence on the pretreated materials in acid and hydrothermal conditions. The evaluation of the washing of the pretreated materials reduced the volume of water initially used in up to 75%, without affecting the final sugar production and the reduction of inhibitory compounds in the residual water, contributing to the viability of the production of cellulosic ethanol from green coconut fiber.