The effect of enzymatic hydrolysis of pretreated wastepaper for bioethanol production

Abstract

Enzymatic hydrolysis of waste biomass for bioethanol production is considered a decades old traditional, inexpensive, and energy-effective approach. In this study, waste office paper was pretreated with diluted sulfuric acid (H₂SO₄) and hydrolyzed with one of the most available and cost-effective enzymes, cellulase derived from Trichoderma reesei, under submerged static condition. Three different pretreatment approaches—cut into 2 cm², blended with distilled water, and pretreated with diluted H2SO4—have been implemented, and pretreatment with diluted H₂SO₄ was the most effective. Hydrolysis with different concentrations—0.5 M, 1.0 M, 1.5 M, 2.0 M of H₂SO₄—was performed. The maximum glucose content was obtained at 2.0 M H₂SO₄ at 90 min reaction time, and glucose yield was 0.11 g glucose/g wastepaper. The cut paper, wet-blended, and acid-treated wastepaper was hydrolyzed with cellulase enzyme for 2, 4, and 5 consecutive days with 5 mg, 10 mg, 15 mg, and 20 mg enzyme loadings. The maximum glucose content obtained was 9.75 g/l from acid-treated wastepaper, after 5 days of enzymatic hydrolysis with 20 mg enzyme loading and a glucose yield of a 0.5 g glucose/g wastepaper. The wastepaper hydrolysate was further fermented for 6, 8, and 10 hours continuously with Saccharomyces cerevisiae (yeast), and at 10 hours of fermentation, the maximum glucose consumption was 0.18 g by yeast. Further, HPLC analysis of the fermented medium presented a strong peak of bioethanol content at 16.12 min. The distillation of bioethanol by rotary evaporator presented 0.79 ml bioethanol/fermented solution, which indicated the conversion efficiency of 79%.