abstract
Cationic polyacrylamides (c-PAMs) are commonly used industrial flocculants. We have
recently shown that they can significantly accelerate both the cellulase mediated hydrolysis
of bleached paper fiber and the amylase catalyzed hydrolysis of cornstarch. A negative
attribute is that they also agglomerate the fibers, which reduces fiber surface area.
However, agitating the medium breaks up the flocs and removes this obstacle. The fibers
are initially attacked by the enzyme at the kinked regions, which makes the fiber length
drop rapidly. Because flocs are more difficult to form with shorter fibers, it is advantageous
to delay the addition of c-PAM until the fiber is first shortened by the enzyme. The rate
acceleration provided by the c-PAM is largely independent of its cationicity for both
cellulose and amylase applications. It is proposed that the mechanism involves “patching”,
a well-established phenomenon in paper science where the cationic c-PAM reduces the
negative charge of the fiber. As the enzyme is also negative, patching reduces the zeta
potential at the fiber surface and minimizes the charge repulsion between fiber and
enzyme. Hence, the c-PAM indirectly promotes enzyme binding, which increases the rate
of hydrolysis.
abstractCationic polyacrylamides (c-PAMs) are commonly used industrial flocculants. We haverecently shown that they can significantly accelerate both the cellulase mediated hydrolysisof bleached paper fiber and the amylase catalyzed hydrolysis of cornstarch. A negativeattribute is that they also agglomerate the fibers, which reduces fiber surface area.However, agitating the medium breaks up the flocs and removes this obstacle. The fibersare initially attacked by the enzyme at the kinked regions, which makes the fiber lengthdrop rapidly. Because flocs are more difficult to form with shorter fibers, it is advantageousto delay the addition of c-PAM until the fiber is first shortened by the enzyme. The rateacceleration provided by the c-PAM is largely independent of its cationicity for bothcellulose and amylase applications. It is proposed that the mechanism involves “patching”,a well-established phenomenon in paper science where the cationic c-PAM reduces thenegative charge of the fiber. As the enzyme is also negative, patching reduces the zetapotential at the fiber surface and minimizes the charge repulsion between fiber andenzyme. Hence, the c-PAM indirectly promotes enzyme binding, which increases the rateof hydrolysis.
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