Biomedical Engineering Reference
In-Depth Information
proteins. ESI-MS analysis found that this enzyme had the highest similarity with
“
-(1-3,1-4)-exoglucanase (AAF79936) in maize coleoptiles. The comprehensive
comparisons of species, molecular weight, enzyme activity, and other characteristics
illustrated that they may be the same protein. The optimum reaction conditions for
this enzyme are 40
ı
C and pH 6.0, and this characteristic enables potential appli-
cations in simultaneous saccharification and fermentation of cellulose because it
relieves the inconsistent temperature of
-Exoglucanase
can promote the simultaneous saccharification and fermentation and enzymatic
hydrolysis, especially simultaneous saccharification and fermentation.
“
-exoglucanase and yeast.
“
2.9.3
Hydrophobic Protein
Fresh cornstalks contain various proteins; in addition to the structural proteins and
zymoproteins, they have hydrophobic proteins. Han and Chen obtained several
kinds of hydrophobic proteins from the total proteins of fresh cornstalks; these pro-
teins had strong adsorption of lignin. The molecular weights of these proteins ranged
from 15 to 35 kDa. ESI-MS analysis of protein with a molecular weight of 18.5 kDa
showed that the protein and corn lipid body-associated protein L2 (P21641) had a
high degree of similarity. It can be concluded that they were the same protein by
comprehensive analysis of the protein characteristics, species source, and so on.
Structural analysis showed that the protein had an amphiphilic structure, 46-122
amino acids consisted of the significant hydrophobic region, while 1-46 amino acids
at N-terminal and 122-187 amino acids at C-terminal were hydrophilic. Therefore,
it can be inferred that, in the hydrophilic-hydrophobic interface, the protein will self-
assemble into amphiphilic film. Hydrophobic protein is without cellulase activity. It
can be adsorbed onto lignin and steam-exploded straw but cannot be adsorbed onto
microcrystalline cellulose. It has a synergistic effect with cellulase in the enzymatic
hydrolysis of steam-exploded straw but has no effect on the enzymatic hydrolysis
of microcrystalline cellulose. Principle analysis showed that hydrophobic protein
may play a role in the enzymatic hydrolysis of steam-exploded straw through the
combination with lignin, reducing the nonspecific adsorption of cellulase on the
substrate, particularly exonuclease and beta-glucosidase.
In view of the plentiful proteins in plants, as well as the possible synergy between
the plant zymoprotein and exogenous cellulase in the enzymatic hydrolysis of
lignocellulose, Chen et al. studied the application of vegetable protein in cellulose
degradation for several years and had some success. Di Lu performed some research
on the change of content of the apoplast protein of corn straw during storage and the
impact on
Penicillium expansum
cellulase activity; it was found that the apoplast
protein and
Penicillium expansum
cellulase had obvious synergies, with the new
harvest straw apoplast protein having the most obvious synergies [
72
]. Han and
Chen [
71
,
73
] found that in vitro autolysis producing glucose as the main product
also happened in the fresh corn straw; autolysis substrates accounted for 2.56 %
of the straw dry weight; these autolysis substrates were mainly cellulose and the
