Page 80 - Lignocellulosic Biomass to Liquid Biofuels

Pretreatment of lignocellulosic biomass for efficient enzymatic saccharification of cellulose 55

improving the efficiency and reducing energy consumption. However,
the process complexity and cost should be considered for such combina-
tions. To develop new pretreatment technology or improve the currently
existing technologies, it is recommended that the molecular mechanisms
of biomass recalcitrance should be investigated in depth, particularly to
elucidate how hemicelluloses and lignin protect cellulose at microscale.
Such elucidation may guide the improvement of pretreatment process.
Moreover, process integration also should be considered to reduce water
and energy consumption, and generation of waste solid and water. One
example of such process integration is the consolidated bioprocessing
(CBP), which integrates the conversion of lignocellulose into desired pro-
ducts in one step without added enzymes. CBP has been widely recog-
nized as the ultimate configuration for low-cost hydrolysis and
fermentation of cellulosic biomass [190]. Another promising way is to
integratedly utilize biomass components for production of different pro-
ducts. To achieve this objective, fractionation of biomass is the most cru-
cial step. Organosolv and combination of acid and alkaline pretreatment
may obtain good fractionation of biomass. However, more evaluation and
optimization should be done to increase the economic feasibility.

Acknowledgments
The authors are grateful for the supports of this work by National Natural Science
Foundation of China (Nos. 21808123, 21506117, and 21878176) and the National
Energy Administration Project (No. NY20130402).

References
[1] S. Sun, S. Sun, X. Cao, R. Sun, The role of pretreatment in improving the enzymatic
hydrolysis of lignocellulosic materials, Bioresour. Technol. 199 (2016) 49 58.
[2] R. Sindhu, P. Binod, A. Pandey, Biological pretreatment of lignocellulosic biomass—
an overview, Bioresour. Technol. 199 (2016) 76 82.
[3] H. Ma, W.-W. Liu, X. Chen, Y.-J. Wu, Z.-L. Yu, Enhanced enzymatic saccharifica-
tion of rice straw by microwave pretreatment, Bioresour. Technol. 100 (2009)
1279 1284.
[4] Y. Zheng, J. Shi, M. Tu, Y.-S. Cheng, Principles and development of lignocellulosic
biomass pretreatment for biofuels, Adv. Bioenergy 2 (2017) 1 68.
[5] B. Yang, C.E. Wyman, Pretreatment: the key to unlocking low-cost cellulosic etha-
nol, Biofuels Bioprod. Biorefin. 2 (2008) 26 40.
[6] P. Alvira, E. Tomas-Pejo, M. Ballesteros, M.J. Negro, Pretreatment technologies for
an efficient bioethanol production process based on enzymatic hydrolysis: a review,
Bioresour. Technol. 101 (2010) 4851 4861.