Enhanced enzyme saccharification of Sorghum bicolor straw using dilute alkali pretreatment

Abstract

The impacts of varying pretreatment parameters (temperature, time, and alkalinity) on enzymatic hydrolysis of sorghum straw were investigated. Following pretreatment, both solids and lignin content was found to be inversely proportional to the severity of the treatments. Higher temperatures and alkali strength were quintessential for maximising sugar recoveries from enzyme saccharifications. Total sugar release peaked when sorghum straw was pretreated in 2% NaOH at 121°C for 60min; representing a 5.6-fold higher yield compared to samples pretreated at 60°C in the absence of alkali. Similarly, 4.3-fold increases in total sugars from samples treated with 2% NaOH at 60°C for 90min, confirmed the importance of alkali inclusion. Addition of β-glucosidase and xylanase to saccharification mixtures enhanced reaction rates and final sugar yields, whilst reducing cellulase dosage 4-fold. Saccharification efficiency of pretreated solids approached 90% and 95% (w/w) with as little as 2.5 and 5.0FPU cellulase/g, respectively.