Fungal Glucoamylase for Starch Hydrolysis

Introduction

Starch is a high molecular weight polymer consisting of glucose units linked by alpha-glucosidic bonds. Starch consists of two glucose polymers: amylose and amylopectin. The proportion of the two polymers varies with starch origin, but is generally 15 to 25% amylose and 75 to 85% amylopectin. Amylose is a linear polymer of glucose units linked through alpha-D-1,4 glucosidic bonds. Amylopectin is a branched polymer consisting of alpha-D-1,4-glucosidic bonds with a small number of alpha-1,6-glucosidic linkages present as interchain branch points. Upon hydrolysis, starch is broken down to a spectrum of higher and lower molecular weight oligosaccharides. Complete hydrolysis yields D-glucose. Since enzyme hydrolysis results in maximum glucose yields and improved product quality, essentially all commercial glucose produced today uses glucoamylase catalyzed reactions.

Description

Glucozyme® (E.C.3.2.1.3,1,4-a-D-Glucan glucohydrolase) is a food grade glucoamylase derived from a selected strain of Aspergillus niger var. The enzyme is an exoglucosidase which catalyzes the hydrolysis of both the alpha-D-1,6-GLUCOSIDIC branch points and the predominating alpha-D-1,4-glucosidic linkages of starch. Glucoamylase removes glucose units successively from the nonreducing ends of starch chains and dextrin. The rate at which this hydrolysis occurs is a function of the starch molecule's chain length. Higher molecular weight oligosaccharides are hydrolyzed at a rate faster than those of lower molecular weight. Also, glucoamylase hydrolyzes the linear alpha-D-1,4-glucosidic linkages at a faster rate than the alpha-D-1,6-glucosidic branched linkages. The controlled composition of Glucozyme® makes it possible to hydrolyze starch, amylose, amylopectin, and a wide variety of glucosyl oligosaccharides to glucose in essentially quantitative yields.

Properties

Form	Nonviscous Liquid Form	Amorphous Dry Powder
Solubility	Completely Miscible with Water	Readily Water Soluble
Color	Amber to Light Brown	Light Tan
Odor	Free of Offensive Odor	Free of Offensive Odor
Taste	Free of Offensive Taste	Free of Offensive Taste
Activity	400 DU/ml	500 DU/g

Activators and Cofactors

No activators or cofactors are necessary for the complete activity of Glucozyme®.

Activity

One Diastase Unit (DLT) is that activity which will catalyze the production of glucose in one hour under the conditions of the Glucozyme® Assay. A copy of the Glucozyme® Assay is available upon request.

Effect of pH

Glucozyme® has an optimum pH range of 4.0 to 4.4, under the conditions of the Glucozyme® Assay. The enzyme can effectively hydrolyze starch and dextrin over the pH range of 3.0 to 5.0. In the presence of 30.0% w/w dry basis dextrose, the enzyme demonstrates maximum stability over the pH range of 3.5 to 5.5.

Optimum Range	4.0 to 4.4
Effective pH Range	3.0 to 5.0

Effect of Temperature

Glucozyme® has an optimum temperature range of 58 to 65C. Under the conditions of the Glucozyme® Assay. Excellent stability is exhibited from 40 to 65C. When reaction times are in excess of 24 hours, the recommended reaction temperature is 60C. Temperatures above 80C rapidly inactivate Glucozyme®.

Optimum Temperature Range	58 to 65C
Effective Temperature Range	40 to 65C

Other Enzyme Components

In addition to glucoamylase activity, Glucozyme® is characterized by significant alpha-amylase activity. Acid protease, hemicellulase and cellulase activity have been detected as trace activities.

Transglucosylase

Transglucosylase, i.e., transglucosidase, is an enzyme associated with many glucoamylase enzyme products. Transglucosylase reduces the yield of glucose from starch by forming oligosaccharides with a-D-1,6-glucosidic linkages. The oligosaccharides formed are rehydrolyzed to glucose at a very slow rate, The higher the transglucosylase activity in a amyloglucosidase product, the poorer the conversion of starch to glucose. Glucozyme® is particularly effective in converting starch because it is transglucosylase free.

Storage Stability

The loss of activity is normally less than 10% over three months at room temperature. Storage stability can be extended by storing under refrigeration at 5C.

Applications

Glucose Production	Essentially all commercial glucose production utilizes a dual-enzyme hydrolysis process employing alpha-amylase and glucoamylase such as Glucozyme®
Fermentation Process	Glucose is widely used in industrial fermentation processes as a growth media or nutrient. Citric acid, gluconic acid, lactic acid, fumaric acid, itaconic acid, vitamins such as RIBOFLAVIN and Vitamin B12, certain antibiotics, and other products can be prepared by glucose fermentation. Glucozyme® can convert starch to glucose prior to the fermentation or, in some cases, in the fermentor during fermentation.
Alcohol Production	Glucozyme® is capable of hydrolyzing starch completely into fermentable sugars. Glucozyme® can be used with malt, reducing the total malt requirements, or with bacterial alpha-amylase as a total malt replacement, Glucozyme® supplies a constant source of fermentable sugars for the yeast fermentation.
Brewing	The production of alcohol will taper off during the later stages of Fermentation unless a continuous supply of fermentable sugar is supplied. Glucozyme® will convert nonfermentable dextrin to fermentables, thus increasing alcohol yields and reducing the carbohydrate content of the beer. Glucozyme® can be used to achieve a high degree of attenuation in the production of low carbohydrate and low caloric beer.
Other Applications	Glucozyme® produces fermentable sugars from starch. Glucozyme® is applicable to vinegar production and production of yeast for industrial and food purposes.