Dr. Jiayang Liu, Associate Professor, Huanghuai University, China.

Speech Title: Effective sugar extraction from energy crop bagasse

Abstract: Both sugarcane and sweet sorghum are among the most important energy crops for biorefinery industry. In addition to sugars that are squeezed from the crops, the residual sugars in the bagasse should be reutilized properly as well. This study analyzes the soluble and insoluble sugars in the two bagasses and the efficiency of extraction. There are variations in not only content but also composition of soluble sugar in the two bagasses. Sugarcane bagasse (SCB) contains 40% sugar, while sweet sorghum bagasse (SSB) contains 33% in total by combining three batches of extraction with water. Three types of soluble sugars, namely, sucrose, glucose, and fructose, are present in the two bagasses but with different content. The first batch of extraction could yield as high as 95% of total sugar from the bagasse, and the relatively best extraction condition is by 20 mL water and 2 h. The soluble sugar-free bagasses are then enzymatically hydrolyzed to glucose with varied dosages (0.1-10 mL/g bagasse) of commercial liquid cellulase. A linear correlation (R2>0.95) was observed between enzyme dosage and sugar release, suggesting higher enzyme would result higher sugar release but meanwhile increasing the cost. The highest glucose released from the two bagasses were around 50% at enzyme dosage of 10 mL/g bagasse. The soluble sugar-free SCB is also pre-treated with persulfate in solution with or without Fe²⁺. Persulfate dosage of 0.1 g/g bagasse treatment enhanced hydrolysis of SCB, from 28% to 35%. Introduction of Fe²⁺ does not significantly increase the subsequent hydrolysis. The coexistence of ligninolytic enzyme laccase with cellulase does not provide any enhancement in hydrolysis, either. To better utilize the two bagasses, extraction of soluble sugars with water and then hydrolyze the bagasse to release glucose might be a good option.