Pullulanase Isoamylase

Pullulanase (cf. 4.4.5.1.4) is utilized in the brewing process and in starch hydrolysis. In combination with P-amylase, it is possible to produce a starch sirup with a high maltose content. 

Enzyme preparations from fungi (Aspergillus niger) or from yeast are used in the dairy industry to hydrolyze lactose. Immobilized enzymes are applied to produce milk suitable for people suffering from lactose malabsorption. Milk treated in this way can also be used to make products like skim milk concentrate or ice cream, thus avoiding interference by lactose due to its low solubility. 

In the brewing process, P-glucans from barley increase wort viscosity and impede filtration. Enzymatic endo-hydrolysis reduces viscosity. 

Enzyme preparations isolated from special yeast strains are used for saccharose (sucrose) inver- 

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Acting together with either - debranching enzymes (pullulanase, isoamylase) in fixed bed or with soluble amylose of low m.w. as substrate it is possible to produce maltose syrups of 70-90%. For crystallization the syrups are emiched in m. content to 95% by various fractionation techniques, such as carbon column or cation-exchange chromatography, solvent precipitation, membrane separation or combinations of the latter with ultrafiltration. 

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 major enzymes that have been used for studying structures of starch polymers and fragments from them are the endo-acting a-amylases, the exo-acting glucoamylase and (3-amylases, and the debranching enzymes, isoamylases and pullulanases. These enzymes have varied and diverse specificities that have been extensively studied (see previous sections). 

Pullulanase (EC3.2.1.41) and isoamylase (EC3.2.1.68) are so-called debranching enzymes because they catalyze the hydrolysis of the 1,6 linkages without effect on the 1,4 linkages29 (see Chapter 7). These enzymes are particularly useful in the production of extremely high maltose syrups with maltose levels of 50 to 90%.30 Table 21.3 provides an overview of commercial enzymes used in the com refining process today and typical operating requirements. 

Non-reducing fructose derivative sweeteners. A Hyashibara process (12) subjects a mixture of starch and sucrose to cyclodextringlucosyl-transferase and amylopectin-a-1,6-glucosidase (such as pullulanase or isoamylase). Cyclodextrins are formed as intermediates, but then act as glucosvl donors for attachment to the glucose portion of the... 

The hypothesis that the sugary 1 mutation affects the structural gene for a debranching enzyme is further supported by the isolation of a cDNA of the su 1 gene. However, its deduced amino-acid sequence is similar to a bacterial isoamylase (James et al, 1995) rather than to a pullulanase. 

By use of a debranching enzyme, isoamylase or pullulanase, the a-D-(l — 6)-linkages in amylopectin are broken, thus opening up to beta-amylase action those parts of the amylopectin molecule that are otherwise resistant.14 In this way, syrups of very high maltose content can be made.19... 

Pullulanase Enzyme degrading pnUnlan, a branched starch pullulanase catalyzes the hydrolysis of the a-l,6-glncosidic linkage in a-glucans. Pullulanase preferentially hydrolyzes pnUnlan while isoamylase has a preference for glycogen and amylopectin. See WaUenfels, K Bender, H and Rached, J.R., Pnllnlanase from Aerobacter aerogenes production in a cell-bound state. Pnrification and properties of the enzymes, Biochem. Biophys. Res. 

Shiraishi et al. [51] studied a process of oxidation of glucose to maltose in the presence of P-amylasc and debranching enzyme (pullulanase or isoamylase). Experiments were performed with glucose concentrations of 5-100 kg m" at 450°C and pH = 4.8. External mass resistance was found negligible. Again, stacked monolithic blocks were used. Production of maltose by this method was very efficient. 

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