Hydrolysis of amylopectin by amylolytic enzymes: structural analysis of the residual amylopectin population |
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Authors: | Annabel Bijttebier Jan A Delcour |
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Institution: | Laboratory of Food Chemistry and Biochemistry, and Leuven Food Science and Nutrition Research Centre (LFoRCe), Katholieke Universiteit Leuven, Kasteelpark Arenberg 20—Box 2463, B-3001 Heverlee, Belgium |
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Abstract: | Amylopectin fine structures were studied following limited hydrolysis of gelatinised waxy maize starch by amylases with a different level of inner chain attack (LICA). This was done by size exclusion chromatography as well as by debranching the (partially hydrolysed) amylopectin samples and studying the size distributions of the released chains. α-Amylases from Bacillus amyloliquefaciens and Aspergillus oryzae, with a relatively high LICA, drastically altered amylopectin chain length distribution and reduced the amylopectin molecular size (MS) significantly even at a low to moderate degree of hydrolysis (DH). Porcine pancreatic α-amylase (PPA), with a rather low LICA but a high multiple attack action on amylose, reduced the amylopectin MS much slower. Following hydrolysis by PPA to a DH of 10% and enzymic debranching of the amylopectin residue, several subpopulations of chains consisting of 2-12 glucose units were detected, indicating a multiple attack action on the amylopectin side chains. During the early stages of hydrolysis, the maltogenic Bacillus stearothermophilus α-amylase (BStA) preferentially hydrolysed the exterior chains of amylopectin. However, during the later phases, BStA also hydrolysed inner chains, presumably with a high multiple attack action. The present results clearly show that different enzymes can be used for (limited) conversion of amylopectin into structures differing in molecular weight and chain length distributions. |
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Keywords: | BAA Bacillus amyloliquefaciens α-amylase BCB Bacillus cereus β-amylase BStA Bacillus stearothermophilus maltogenic α-amylase DH degree of hydrolysis DP degree of polymerisation HPAEC-PAD high performance anion exchange chromatography with pulsed amperometric detection LICA level of inner chain attack MS molecular size PPA porcine pancreatic α-amylase RV80 reducing value for a KI-I2 value of 80% of the initial value SEC-RID size exclusion chromatography with refractive index detection TAKA Aspergillus oryzae α-amylase |
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