IMPACT OF CELLULOSE ALLOMORPH ON ENZYMATIC SACCARIFICATION

Ting Cui1, 2, Jihong Li1, 2, Zhipei Yan1, 2, Shizhong Li1, 2*, Menghui Yu1,2

1 Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China

2 Beijing Engineering Research Centre of Biofuels, Tsinghua University, Beijing 100084, China

Abstract

B ack grou n d

Bioconversion of cellulose into glucose or chemicals attracted extensive attentions for the sustainable development of human society in recent decades. The crystal allomorph of cellulose is a key factor to affect cellulose saccharification. However, due to the influence of lignin, hemicellulose and different characterizing methods of literatures, the effect of cellulose allomorph on cellulose saccharification is still confused. Thus, a systematic research on the effect of different cellulose allomorph on enzymatic saccharification is required.

R esu lt s

Multiple approaches, including ionic liquid (IL), ethylenediamine (EDA), glycerol and sodium hydroxide, were used to pretreat α-cellulose in this work. The properties of obtained cellulose (crystallinity index, lattice spacing, specific surface area and wettability) were characterized by X-ray diffraction, BET specific surface area analysis and water contact angle analysis, respectively. The distance of lattice spacing of cellulose III was larger than that of other cellulose samples. The crystallinity and water contact angles of all the cellulose samples were both in the following order: cellulose treated by IL < cellulose treated by NaOH < cellulose treated by EDA <α-cellulose < cellulose treated by glycerol. Cellulose treated by IL with a crystallinity index value of 20%, was very close to amorphous cellulose. After 72 h hydrolysis, the cellulose conversion rates ranged from 43% to 99%. Cellulose treated by IL exhibited a notably efficient hydrolysis profile, followed by cellulose treated by EDA.

Con clu sion

Four cellulose allomorphs were prepared to investigate the effect of crystal form on the cellulose enzyme digestibility in this study. With the integrated experimental characterization, the most feasible enzymatic hydrolysis allomorph was cellulose III, followed by cellulose II, cellulose Iα and Iβ. When the crystal type of cellulose was the same, the crystallinity index was the dominant factor. Low crystallinity index enhanced the enzymatic hydrolysis efficiency of cellulose. Water contact angle was also a feasible characterization to evaluate the enzymatic hydrolysis efficiency of cellulose except for cellulose III. High wettability of cellulose enhanced the enzymatic hydrolysis when crystal allomorph of cellulosic samples was the same.