Evaluation of alkali and cellulose solvent pretreatments for fermentable sugar production from the biomass of Phragmites karka (Retz.) Trin. ex Steud.: a high biomass producing grass

Phragmites karka is one of the fast growing halophytes known to accumulate high biomass in a short span of time. In this study, we evaluated the potential of P. karka biomass from the Chilika Lagoon of India for the production of glucose which can possibly be converted into ethanol. Compositional analysis of biomass of P. karka was carried out and it was found that the biomass contained 33.12% cellulose, 28.17% hemicellulose and 24.81% lignin. For saccharification, the biomass were pretreated with two different pretreatments such as, cellulose solvent -and organic-solvent based lignocellulosic fractionation (COSLIF) and alkali (NaOH). Both of the pretreated biomass were digested with various dosages of cellulase and β -glucosidase enzymes. The enzymatic hydrolysis revealed that COSLIF using 85% phosphoric acid at a solid loading of 1 g biomass to 8 ml acid for 45 min at 50 °C exhibited the best result in terms of glucose release. Cellulase enzyme mixture containing 1 FPU cellulase and 10 IU β -glucosidase was found efficient in releasing 86.16% of glucose from the COSLIF pretreated biomass, whereas with the use of higher dosages of enzyme mixture (60 FPU cellulase and 60 IU β -glucosidase) alkali pretreated biomass could release only 72.65% glucose. The findings in this study addressed the potential use of P. karka as a source of biomass for the second generation ethanol production. Graphical abstract