Breaking Down Biomass: How Pretreatment and Enzyme Strategy Shape Efficient Bioethanol Yields

Abstract

Trichoderma sp. SG2, isolated from the Black Belt soils of Alabama, USA, is a potent natural producer of β-glucosidase and a broad spectrum of cellulolytic and xylanolytic enzymes. This study explored the saccharification of lignocellulosic biomass using crude enzymes from Trichoderma sp. SG2, various pretreatment strategies, mixed feedstock approaches to enhance sugar yield, and enzyme supplementation to reduce costs. Among the pretreatment methods tested for switchgrass, the most effective was sequential H₃PO₄–ethanol, followed by NaOH–H₂SO₄, H₃PO₄–acetone, H₂SO₄–NaOH, and single-agent treatments (H₂SO₄ alone or NaOH alone). Sugar yields were significantly improved by combining pretreated switchgrass with paper powder as a mixed feedstock. The highest glucose (15.8 g/L) and xylose (3.8 g/L) yields were achieved at 10% pretreated switchgrass after 72 h. A key finding was the significant cost reduction and enhanced saccharification efficiency achieved by supplementing SG2 crude enzyme with 50% of the recommended commercial enzyme dosage. Acid-pretreated switchgrass hydrolysis with SG2 enzyme and commercial enzyme supplementation emerged as the most effective strategy. These results highlight Trichoderma sp. SG2 as a promising candidate for developing cost-effective enzyme cocktails for lignocellulosic biomass hydrolysis where 30 to 40% cost of ethanol production process is accounted for enzyme cost.