Enzymes pullulanase

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. 

The discovery, shortly thereafter, of the enzyme pullulanase from the bacterium Aerobacter aerogenes helped considerably in further structural analysis of the polysaccharide. Hydrolysis of pullulan by diis enzyme showed that essentially no products containing (l->6)-ff-i>-giucosidic linkages were formed, the preponderant product being maltotriose. It was thus clear that the enzyme hydrolyzes (l->6)-a-D-glucosidic link-... 

For example, debranching enzymes (pullulanase and [Pg.165]

A. behaves like starch or amylose in reactions such as ->hydrolysis, derivatization or physical treatment (modified starches). Application of debranching - enzymes (pullulanase and iso-amylase) opens the possibility of total splitting of the a-1,6-linkages, thus enhancing hydrolysis as well as producing short-chain amyloses fit>m a. on a commercial scale. 

When using branched -> starch polysaccharides, additional application of the - debranching enzymes pullulanase or isoamylase leads to increased yields. Entirely soluble substrates can be reacted economically by continuous flow over immobilized enzyme systems. 

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. 

Saccharification. Saccharifications were performed with amyloglucosidase (AMG) or amyloglucosidase/pullulanase (Dextrozyme) at a dose of 0.18 AG/units/gram DS for 48 hours at 60 C, pH 4.3-4.5. One AG unit is the amount of enzyme which hydrolyzes 1.0 micromole of maltose per minute at 25 C, pH 4.3. 

Roy, I. and Gupta, M.N., Hydrolysis of starch by a mixture of glucoamylase and pullulanase entrapped individually in calcium alginate beads, Enzyme Microbial Tech., 34 (2004) 26-32. 

Mixed enzyme solution - either make up a mixed enzyme solution containing 5000 units of a-amylase and 5 units of pullalanase per millilitre acetate buffer (original method), or, as is usual, separately add 0.5 ml a-amylase reagent and 0.1 ml pullulanase reagent per sample. 

Dextrose yield, however, can be increased by conducting saccharification at a lower solids level where the reverse reaction is minimized. For instance, dextrose yields of 98.8, 98.2, 97.5, and 96.9% dry basis can be achieved at solids levels of 10, 15, 20, and 25%, respectively (10). Low solids operation, however, is not used commercially owing to problems associated with microbial contamination and cost of water removal. Dextrose level can be increased by 0.5—1.5% at normal reaction solids by using an enzyme such as pullulanase (11) or a B. megaterium amylase (12) in conjunction with... 

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). 

Arnosti, C., and D. J. Repeta. 1994a. Extracellular enzyme activity in anaerobic bacterial cultures Evidence of pullulanase activity among mesophilic marine bacteria. Applied and Environmental Microbiology 60 840-846. 

Amino acid sequence relationships between that of branching enzyme (BE) and amy-lolytic enzymes, such as a-amylase, pullulanase, glucosyltransferase and cyclodextrin glucanotransferase, especially at those amino acids believed to be contacts between the substrate and the amylase family enzymes, were first reported by Romeo et al.283 Baba et al.284 reported that there was a marked conservation in the amino acid sequence of the four catalytic regions of amylolytic enzymes in maize endosperm BEI. As shown in Table 4.12, four regions that putatively constitute the catalytic... 

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