Efficient Saccharification of Wheat Straw Pretreated by Solid Particle-Assisted Ball Milling with Waste Washing Liquor Recycling

Abstract

Wheat straw was pretreated using ball milling (BM) promoted by solid particles (NaOH, NaCl, citric acid). NaOH-BM showed best synergistic interaction effect, due to the interaction of alkali solid particles in β-1,4-glycosidic bonds among cellulose molecules induced by BM. NaOH-BM pretreatment decreased crystallinity and average particle size from 46% to 21.4% and 398.3 μm to 50.57 μm in 1 h milling, respectively. After 4 h milling, reducing-end concentration of cellulose increased by 4.8 times from 12.5 μM to 60.2 μM, with glucose yield increased by 3.1 times from 26.6% to 82.4% for 72 h enzymatic hydrolysis at cellulase loading of 15 FPU/g. Pretreated sample was washed and washing liquor was further recycled for the chemical hydrolysis of partial pretreated sample at 121 °C for 30 min, with 99.4% glucose yield at the first cycle. BM assisted with alkali particles is an effective approach for improving biomass enzymatic saccharification.

Keywords: Pretreatment, solid particle, ball milling, enzymatic hydrolysis, Wheat straw