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Effect of liquid hot water pretreatment severity on properties of hardwood lignin and enzymatic hydrolysis of cellulose
Author(s) -
Ko Ja Kyong,
Kim Youngmi,
Ximenes Eduardo,
Ladisch Michael R.
Publication year - 2015
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.25349
Subject(s) - lignin , cellulose , chemistry , hardwood , hydrolysis , enzymatic hydrolysis , lignocellulosic biomass , cell wall , organic chemistry , biochemistry , botany , biology
Lignin, one of the major components of lignocellulosic biomass, plays an inhibitory role on the enzymatic hydrolysis of cellulose. This work examines the role of lignin in pretreated hardwood, where extents of cellulose hydrolysis decrease, rather than increase with increasing severity of liquid hot water pretreatment. Hardwood pretreated with liquid hot water at severities ranging from log R o = 8.25 to 12.51 resulted in 80–90% recovery of the initial lignin in the residual solids. The ratio of acid insoluble lignin (AIL) to acid soluble lignin (ASL) increased and the formation of spherical lignin droplets on the cell wall surface was observed as previously reported in the literature. When lignins were isolated from hardwoods pretreated at increasing severities and characterized based on glass transition temperature (T g ), the T g of isolated lignins was found to increase from 171 to 180°C as the severity increased from log R o = 10.44 to 12.51. The increase in T g suggested that the condensation reactions of lignin molecules occurred during pretreatment and altered the lignin structure. The contribution of the changes in lignin properties to enzymatic hydrolysis were examined by carrying out Avicel hydrolysis in the presence of isolated lignins. Lignins derived from more severely pretreated hardwoods had higher T g values and showed more pronounced inhibition of enzymatic hydrolysis. Biotechnol. Bioeng. 2015;112: 252–262. © 2014 Wiley Periodicals, Inc.