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Modeling cassava starch saccharification with amyloglucosidase

  • Gisella Maria Zanin
  • Flávio Faria De Moraes
Session 3 Bioprocessing Research

Abstract

A solution of α-amylase liquefied cassava starch, 30% (w/v), was saccharified with amyloglucosidase at 45°C, pH 4.5, in a batch reactor in the presence and absence of added glucose. Reactor conversion results were modeled with a multisubstrate model that considers intermediate dextrins of starch hydrolysis, reversibility of some reactions, substrate and product inhibition, and competition among dextrins and isomaltose formation. Kinetic parameters were obtained from initial velocity saccharification tests at different starch concentrations and from the literature. The model can represent well the saccharification of cassava starch even in the presence of a great excess of glucose (100 g/L), added to test its capability.

Index Entries

Cassava starch amyloglucosidase saccharification modeling 

Nomenclature

CA

liquefied starch concentration, g/L

CAo

initial starch concentration, 300 g/L

Cg

glucose concentration, g/L

Cga

concentration of added glucose, g/L

Cgi

glucose concentration at the start of saccharification, g/L

E

enzyme concentration, mL of enzyme stock solution/L of substrate solution

f

ratio of molecular weights for the anhydroglucose unit in starch and glucose, f = 162/180 = 0.9

G

glucose molar concentration, mol/L

G2

maltose molar concentration, mol/L

G3

maltotriose molar concentration, mol/L

G4

susceptible oligosaccharides molar concentration, mol/L

G6

resistant oligosaccharides molar concentration, mol/L

GI

isomaltose molar concentration, mol/L

Geq, G2eq, G3eq, Gleq

quilibrium molar concentration for glucose, maltose, maltotriose, and isomaltose, respectively, mol/L

kcat

reaction rate constant related to product formation, ol/(h·mL of enzyme)

Keq2, Keq3, KeqI

equilibrium constants for maltose (mol/L), maltotriose (mol/L), and isomaltose (L/mol), respectively

Ki

product (glucose) inhibition constant, mol/L

Km2, Km3, Km4, Km6

Michaelis-Menten constants for maltose, maltotriose, susceptible oligosaccharides, and resistant oligosaccharides, respectively, mol /L

KS

substrate inhibition constant, mol/L

MG

molecular weight of glucose, 180 g/gmol

n

average degree of polymerization, dimensionless

r2, r3, r4, r6, r1

rate of reaction for maltose, maltotriose, susceptible oligosaccharides, resistant oligosaccharides, and isomaltose, respectively, mol/(L·h)

t

reaction time, h

V

initial rate of glucose production, g/(L·h)

VIM

second-order rate constant for isomaltose, L2/(mol·h·mL of enzyme)

Vm2, Vm3, Vm4, Vm6

maximum velocity constants associated with the reaction rate of maltose, maltotriose, susceptible oligosaccharides, and resistant oligosaccharides, respectively, mol/(h·mL of enzyme)

XA

conversion of liquefied starch to glucose, %

α

parameter in Eq. (22), a = (CAo/kcat) (1-Km/K+CAo/KS), mL of enzyme·h/L

β

parameter in Eq. (22), β = (Km/kcat) (1 + Cgi/Ki + CAo/Ki), mL of enzyme·h/L

γ

parameter in Eq. (22), γ = C Ao 2 /(2K S kcat), ml of enzymeh/L

τb

normalized reaction time, τb = E·t, mL of enzyme·h/L

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Copyright information

© Humana Press Inc. 1996

Authors and Affiliations

  • Gisella Maria Zanin
    • 1
  • Flávio Faria De Moraes
    • 1
  1. 1.Chemical Engineering DepartmentState University of MaringáMaringá, PRBrazil

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