Bioethanol production from waste paper acid pretreated hydrolyzate with xylose fermenting Pichia stipitis

This study evaluates acid pretreated waste paper hydrolyzate as feedstock for bioethanol production. The presence of 70.12 ± 4.88% carbohydrates (holocellulose) makes waste paper a prospective and renewable biomass for bioethanol production. The waste paper was found to contain α-cellulose (61.5 ± 3.49%), pentosans (7.42 ± 0.36%), lignin (16.33 ± 0.96%), ash (12.50 ± 0.33%) and moisture (8.28 ± 0.63%). Conditions for the dilute acid pretreatment of waste paper were optimized by varying solid/liquid ratio 1:8–1:14 (w/v), reaction time 01–06 h, and sulfuric acid concentration 0.005–1.00 N at 120 °C in an autoclave. The conditions optimized for acid hydrolysis of waste paper were 0.50 N H2SO4 at 120 °C for 02 h reaction time keeping biomass:acid ratio 1:10 (w/v) for recovery of reducing sugars from waste paper hydrolyzate. Fermentation of acid hydrolyzate of waste paper with Pichia stipitis under optimum condition resulted in ethanol production 3.73 ± 0.16 g/l with 77.54 ± 4.47% of fermentation efficiency.