Starch conversion

In recent years, the conversion of starch to fructose has become a very important commercial process. High-fructose corn syrup (HFCS) is approximately twice as sweet as sucrose. It is used in soft drinks, canned fruits, lactic acid beverages, juice, bread, ice cream, frozen candies, and so on. HFCS can be obtained from a variety of cereals and vegetables, such as corn, wheat, rice, potatoes, and cassava. Corn is the most important source of HFCS because of low costs and excellent utilities of its by-products, corn meal, oil, gluten, germ, and fiber. 

Cellulosic wastes have great potential as a feedstock for producing fuels and chemicals. Cellulose is a renewable resource that is inexpensive, widely available and present in ample quantities. Large amounts of waste cellulose products are generated by commercial and agricultural processes. In addition, municipal facilities must treat or dispose of tremendous quantities of cellulosic solid waste. 

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Malted barley contains a- and P-amylases along with proteases and phytases. Most standardi2ed microbial en2yme preparations for industrial starch conversion contain approximately 100 times more amylase activity than malt. In beermaking, malt is not just valuable for its en2ymes but also for flavor compounds. 

The growth in volume of the enzyme business from 1980 to 1990 is estimated to be 5—10% per year. The estimated worldwide enzyme sales per industry are shown in Table 7. The detergent and starch conversion industries are by far the most important, and account for 60% of total enzyme sales. Five principal industries account for around 85% of enzyme sales, whereas the remaining sales are spread over many different industries. 

Parameters for tree differentiation are autumn colours and bud formation (with equal bearing). Parameters for fruit differentiation are degree and hue of blush, yellow ground (background) colour, shape of fruit, sheen, starch conversion, differentiation score on crystallisation pictures and luminescence. 

The problem of crystallizing dextrose from starch conversion liquor in a form which would allow separation from the viscous mother liquor was attacked in the latter part of the nineteenth century by various workers. The most successful efforts were made by Behr in 1881.3 Corn starch was hydrolyzed at low concentration, the refined product was concentrated, seeded with a very small proportion of pure anhydrous dextrose crystals, and it was then allowed to stand without agitation in heated rooms. Care was taken to exclude any traces of dextrose hydrate crystals. After several days the crystalline magma was separated and washed in centrifugal filters. By this means individual crystals of anhydrous dextrose of suitable size were obtained and the product... 

Fig. 4.—Alpha dextrose monohydrate from refined starch conversion liquor. Magnification, 50.

Anhydrous alpha dextrose may be obtained by drying the hydrate in a stream of warm air.6 For a very pure grade of the anhydrous product a better method is used which consists of crystallizing from solution in a vacuum pan at a temperature above 50°C.1314 This temperature is the hydrate-anhydrous transition point. Dextrose from the first crystallization of the starch conversion liquor is dissolved in water to give about a 60 % solution which is treated with a small quantity of activated carbon... 

Isoamylase [9067-73-6] (glycogen-6-glucanohydrolase) and pullulanase [9012-47-9] (pullulan-6-glucanohydrolase) hydrolyzes a-l,6-glucosidic bonds of starch. When amylopectin is treated with a pullulanase, linear amylose fragments are obtained. Using a heat- and acid-stable pullulanase in combination with saccharifying enzymes makes the starch conversion reactions more efficient (71). 

The applications of enzymes can be classified into three major categories industrial enzymes, analytical enzymes, and medical enzymes. In this chapter, we review several industrial processes, utilizing industrial enzymes such as starch conversion and enzymatic hydrolysis of celluloses. Before we discuss the enzymatic hydrolysis of starch and cellulose, we review the organic chemistry of carbohydrates. 

Buchan, J.L. and Savage, R.J., Paper chromatography of starch-conversion products, Analyst, 77,401, 1952 Chem. Abs., 48, 8568c, 1954. 

The performance of cellulase and amylase immobilized on siliceous supports was investigated. Enzyme uptake onto the support depended on the enzyme source and immobilization conditions. For amylase, the uptake ranged between 20 and 60%, and for cellulase, 7-10%. Immobilized amylase performance was assessed by batch kinetics in 100-300 g/L of com flour at 65°C. Depending on the substrate and enzyme loading, between 40 and 60% starch conversion was obtained. Immobilized amylase was more stable than soluble amylase. Enzyme samples were preincubated in a water bath at various temperatures, then tested for activity. At 105°C, soluble amylase lost -55% of its activity, compared with -30% loss for immobilized amylase. The performance of immobilized cellulase was evaluated from batch kinetics in 10 g/L of substrate (shredded wastepaper) at 55°C. Significant hydrolysis of the wastepaper was also observed, indicating that immobilization does not preclude access to and hydrolysis of insoluble cellulose. 

Swinkels JJM. In van Beynum GMA, Roels JA, eds. Starch Conversion Technology. New York, NY Marcel Dekker 1985 15. 

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