Simultaneous isolation of cellulose and lignin from wheat straw and catalytic conversion to valuable chemical products

Entry
H
2
SO
4
 concentration (wt%)
Sugar
First stage
Second stage
Xylose
Mannose
Arabinose
Galactose
Glucose
1
0.5
/
+ + 
+ 
+ 
Trace
Trace
2
0.5
1.5
+ + + 
+ + 
+ + 
+ 
Trace

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Page 11 of 13
Yu et al. Appl Biol Chem (2021) 64:15 
the amount of sugar produced was considerably less. It 
has been reported that the hydrolysis of hemicellulose 
produces furfural and oligosaccharide besides monosac-
charide [
18
]. However, almost no furfural was detected 
in the liquor. Therefore, we speculate that hemicellulose 
was primarily transformed into a large number of oli-
gosaccharides such as xylooligosaccharides, arabinoo-
ligosaccharides and mannooligosaccharides. Factually, 
the formation of a large number of substances with a 
molecular weight of > 300 Da was detected by HPLC–
MS (see Additional file 
1
: Fig. S4). The oligosaccharides 
derived from hemicellulose possibly still connect with 
lignin via a covalent bond, which led to difficulty in the 
precipitation of lignin. As expected, the production of 
sugars was improved with increase in acid concentration 
and temperature, and the hydrolysis of hemicellulose was 
enhanced using the two-stage process. Undoubtedly, the 
improvement in the hydrolysis of hemicellulose was ben-
eficial to separating hemicellulose and lignin. Therefore, 
higher lignin yield was observed (Table 
6
, entry 1). The 
dependence of lignin yield on the hydrolysis of hemicel-
lulose confirmed that a covalent bond may exist between 
lignin and the insufficient hydrolysis product derived 
from hemicellulose.