Cationic polyacrylamides increase the rate of liquefaction and hydrolysis of cornstarch

Abstract

in Wiley Online Library (wileyonlinelibrary.com).Cationic polyacrylamides (c-PAMs) bind to starch granules and decrease the temperature for the onset of gelatinization by 8 C. c-PAM increases the binding of -amylase to cornstarch; the rate of cornstarch hydrolysis also increases. By analogy to previous work on the c-PAM promoted hydrolysis of cellulose, it is proposed that the polymer reduces the charge on the surface of starch through a charge-patch mechanism. Because both enzyme and substrate are negatively charged, the bound c-PAM reduces the charge repulsion experienced by the approaching enzyme, which leads to stronger enzyme-substrate binding and faster hydrolysis. Overall, the c-PAM reduces enzyme dose by up to 62% under the conditions used. There is a mirror image relationship between the viscosity of the medium and the hydrolysis rate, which allows optimization of these parameters with enzyme and c-PAM dosage. Low c-PAM levels increase viscosity by agglomerating the substrate, but the viscosity drops at higher c-PAM concentration.

Poly(diallyldimethylammonium chloride) Accelerates α-Amylase-Induced Cornstarch Liquefaction

“…The viscosity of cornstarch spikes during gelatinization. Through a study of c-PAMs of differing cationicities, we showed that there is an inverse relationship between viscosity and glucose production . The higher viscosity lowers the rate of hydrolysis, probably by slowing down diffusion.…”

“…The principal purpose of the polymers is to increase the rate of hydrolysis of either cornstarch or cellulosic fiber . Because the gelatinization of cornstarch is rapid, an appreciable amount of colloidal material is formed and the agglomeration of these compounds can be enhanced by the polymer, leading to an increase in viscosity.…”

“…Each suspension was centrifuged at 4 °C at 13 400 relative centrifugal force (RCF) for 10 min, and the protein content of the supernatant was determined. p-DADMAC binding to cornstarch was measured by the solution depletion method , as described earlier . Starch (1–15%) was shaken with a p-DADMAC solution (50 ppm) at 25 °C for 30 min and centrifuged at 3000 RCF for 15 min.…”

“…The amount of p-DADMAC adsorbed to the starch was determined from the difference in charge in the supernatant between p-DADMAC alone and that from the starch/p-DADMAC samples; the analytical uncertainty was about 6%. The binding of enzyme to p-DADMAC-treated starch was measured as before by adding the polymer to a suspension of cornstarch in water at 4 °C. Enzyme was added and the suspension shaken at 4 °C for 30 min.…”

“…We have demonstrated that the enzymatic hydrolysis of cornstarch and cellulosic fiber can be accelerated by cationic polyacryamides (c-PAMs). − The polymer reduces the negative charge on the surface of the substrate through a charge-patch mechanism, , which increases productive enzyme–substrate binding. The hydrolysis rate rises by about the same amount, which implies a cause-and-effect relationship.…”