Efficient Production of Fermentable Sugars from Common Reed Biomass Through Hydrothermal and Citric Acid Pretreatment Processes

Production of fermentable sugars from renewable lignocellulosic biomass could provide a sustainable substrate for biofuel production by microbial fermentation. However, the inherent structure of lignocellulose largely hinders enzymatic saccharification efficiency to obtain sugars, thus the development of efficient pretreatment methods to reduce biomass recalcitrance is an important issue. In this study, the effects of two typical processes including hydrothermal (HTP) and citric acid pretreatments (CAP) on the enzymatic hydrolysis yield of reed biomass were investigated. The results indicate that, when performing HTP at 180 °C for 120 min to deconstruct reed, the pretreated biomass led to a higher glucose yield of 87.1% after 72 h enzymatic hydrolysis with cellulase (10 FPU/g substrate). Furthermore, under the pretreatment conditions with 6% (w/v) citric acid, 150 °C, and 60 min, the glucose yield of pretreated reed was 63.4% after hydrolysis with cellulase (10 FPU/g substrate). In this case, adding Tween 80 (100 mg/g substrate) significantly facilitated the enzymatic saccharification activity resulting in the glucose yield of CA-pretreated reed to 84.2%. Compared with the untreated reed, the glucose yield of pretreated residues after HTP and CAP was largely improved by 4.97–5.18 folds which was mainly due to the enhanced crystallinity (50.0–53.2% vs. 45.9%). The total fermentable sugars of 34.7–34.8 g can be produced from 100 g of raw reed biomass based on the proposed HTP and CAP processes. The mechanism of enhanced enzymatic hydrolysis after pretreatments was elucidated through physicochemical characterization techniques. In summary, the proposed pretreatments show high potential application for biorefinery from renewable, abundant reed biomass.