The production of fermentable sugar and bioethanol from acacia wood by optimizing dilute sulfuric acid pretreatment and post treatment

Abstract

Dilute sulfuric acid pretreatment was applied to make acacia wood susceptible to enzymatic hydrolysis. The optimal conditions for pretreatment were determined using a statistical approach; the maximum glucose yield (predicted: 53.8%; experimental: 54.5%) was obtained with 0.05% sulfuric acid at 200 °C for 5 min. This optimal condition yielded higher hemicellulose recovery in a short time compared to hydrothermal treatment, but the glucose yield was not enough to make fermentable sugar. However, application of mechanical refining to the pretreated solid and the addition of soy protein to the enzymatic hydrolysis led to the highest glucose conversion (73.8%) at 10 FPU (Cellic® CTec3)/g of glucan, and maximum conversion yield to ethanol reached 94.9% at 5 FPU. Considering this method’s comparable glucose convertibility, even from lignin rich woody biomass, ability to recover hemicellulose, and lower enzyme requirement, dilute acid pretreatment can serve as a direct and promising route of producing acacia sugar.