Enzymes for starches

Enzyme-enzyme conversion employs heat and an enzyme for starch liquefaction in place of acid. This is the most common form of com processing today Subsequent hydrolysis is by enzymes, as above. The choice of hydrolytic system depends upon economics and the kind of endproduct desired. Enzymes are usually inactivated by heating the symp to 75-80°C, with the exception of the heat-stable a-amylases that have come on the market in the last 10 to 15 years. 

Bradford Enzymes. [Original Bradford Soiqp Works] Bacterial pha-amylase enzymes for starch removal. 

Dextrozyme. [Novo Nordisk] Pullula-nase/amyloglucosidase enzyme for starch industry. 

Rhozymc . [Genencor Int l.] Amylase, pentosanase-hexonase, or jHDiease enzymes for starch lique tion, food processing, desizing textiles. 

T rmamyl . [Novo Nordisk] Alpha-amylase heat-stable enzyme for starch liquefaction, for laundry and dishwash detergents, alcohol, brewing, and textile industries. 

Asperzyme. [Enzyme Development] Enzyme for starch conversion. 

Tenase . [Solvay Enzymes] Alpha-amylase enzyme for starch liquefaction. 

Recent research and knowledge has been sampled about the functional significance of the regulation of biosynthetic enzymes for starch, it has been concluded that it could be possible to alter the biosynthetic process (2). 

Richardson TH, Tan X, Frey G, Callen W, Cabell M, Lam D, Macomber J, Short JM, Robertson DE, Miller C (2002) A novel, high performance enzyme for starch liquefaction discovery and optimization of a low pH, thermostable alpha-amylase. J Biol Chem 277 26501-26507 Robertson DE, Murphy D, Reid J, Antony MM, Link S, Swanson RV, Warren PV, Kosmotka A (1999) Esterases. US Patent 5,942,430 Roels JA, van Tilburg R (1979) Temperature dependence of the stability and the activity of immobilized glucose isomerase. ACS Symp Ser 106 147-172 Rohm O (1915) Verfahren zum Reinigen von Waschestucken aller Art. Patent DE 283923... 

Teague, W.M., and Bmmm, P.J. 1992. Commercial enzymes for starch hydrolysis products. Pages 45-78 in Starch Hydrolysis Products. F.W. Schenck and R.E. Hebeda (eds.). VCH Publishers, New York. 

Uses Wetting agent, rewetting agent with exc. leveling props, for textile processing activates enzymes for starch removal Properties Liq. 

In the EHE process, a starch slurry is prepared and calcium, as the chloride or hydroxide, is added as a cofactor to provide heat stabiUty to the enzyme. The starch slurry is passed through a stream injection heater and held at temperature for about one hour. The resulting 4—8 DE hydrolyzate is then subjected to a heat treatment in a hoi ding tube, redosed with enzyme, and allowed to react for one hour to a DE level of 10—15. 

In the early years of the chemical industry, use of biological agents centered on fermentation (qv) techniques for the production of food products, eg, vinegar (qv), cheeses (see Milk and milk products), beer (qv), and of simple organic compounds such as acetone (qv), ethanol (qv), and the butyl alcohols (qv). By the middle of the twentieth century, most simple organic chemicals were produced synthetically. Fermentation was used for food products and for more complex substances such as pharmaceuticals (qv) (see also Antibiotics). Moreover, supports were developed to immobilize enzymes for use in industrial processes such as the hydrolysis of starch (qv) (see Enzyme applications). 

Enzymes in Pulp and Paper Production. Enzyme-modified starch has been used for adhesives to strengthen paper base and for surface coating. Developments since the late 1980s of further uses of enzymes in papermaking include pitch control and bleach boosting, (see Paper Pulp). 

The characteristics of a starch can be modified by chemical, physical, and/or enzyme treatment to enhance or repress its intrinsic properties, or to impart new ones. This capability for modification has been a necessary factor in developing new uses for starch and in maintaining old markets. 

Saliva begins the process of chemical digestion with salivary amylase. This enzyme splits starch molecules into fragments. Specifically, polysaccharides, or starches, are broken down into maltose, a disaccharide consisting of two glucose molecules. Salivary amylase may account for up to 75% of starch digestion before it is denatured by gastric acid in the stomach. 

Fig. 2.2 Enzyme reactors prepared by LbL assembly (A) reactor on quartz plate for color-indication of glucose (B) multi-enzyme reactor for starch digestion on ultrafilter. Adapted from [26], M. Onda etal, Biotechnol. Bioeng. 1996, 57, 163 and [27], M. Onda et al.,J. Ferment. Bioeng. 1996, 82, 502.

Pacsu4 5 has suggested a structure for starch involving a small number of non-cyclic hemiacetal linkages, the number being presumably sufficient to account for the number of endgroups determined by the methylation method. Halsall, Hirst and Jones6 have commented on this structure, however, and have shown it to be incompatible with the results of periodate-oxidation studies. In addition, these authors pointed out that it would be difficult to explain enzymic hydrolysis and dextrin formation on the basis of such a structure. 

In this chapter we describe the use of pea seeds to express the bacterial enzyme a-amylase. Bacterial exoenzymes like the heat stable a-amylase from Bacillus licheni-formis are important for starch hydrolysis in the food industry. The enzymatic properties of a-amylase are well understood [13,14], it is one of the most thermostable enzymes in nature and it is the most commonly used enzyme in biotechnological processes. Although fermentation in bacteria allows highly efficient enzyme production, plant-based synthesis allows in situ enzymatic activity to degrade endogenous reserve starch, as shown in experiments with non-crop plants performed under greenhouse conditions [12,15]. Finally, the quantitative and sensitive detection of a-amylase activ-... 

Based on these results, several different commercial and experimental protease samples were obtained from enzyme companies and were tested for starch yield using the enzymatic corn wet milling process (Figure 3). Two commercial protease enzymes (enzymes A and C) gave starch yields comparable to the conventionally wet milled sample. Pasting properties, residual protein in starch, and surface characteristics of starch samples obtained from... 

Figure 4. A. Water relationships and diffusion paths for starch-plastic film in a moist environment. Lightly shaded area indicates thin water layer on surface arrows show diffusion paths for enzymes produced by microbes on film surface. B. Same as 4 A., except that film is inunersed in water.

A great advantage of spectrophotometric assays is that they can be carried out in microtiter plates or as filter paper assays, thus allowing a high sample throughput coupled with small sample volumes. Such systems were used for example for the screening of epoxide hydrolases [34]. A classical example of activity tests is for amylolytic enzymes where starch agar plates are stained with iodine after a certain reaction time. The radius of clear spots is a measure of the reaction rate [35]. 

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