Instituto de Tecnología en Polímeros y Nanotecnología (ITPN), Facultad de Ingeniería, Universidad de Buenos Aires, Capital Federal, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.
Instituto de Tecnología en Polímeros y Nanotecnología (ITPN), Facultad de Ingeniería, Universidad de Buenos Aires, Capital Federal, Argentina.
Carbohydr Polym. 2014 Feb 15;102:80-7. doi: 10.1016/j.carbpol.2013.11.013. Epub 2013 Nov 15.
Waxy maize starch was subjected to α-amylase (Bacillus licheniformis) hydrolysis in buffered medium to determine the evolution of reaction in quantitative terms and also in terms of the morphology and crystallinity of the partially hydrolyzed starch granules. Gathered data allowed studying the pattern of action of this α-amylase over waxy maize starch granules, with particular focus on a preferential hydrolysis of the amorphous regions of starch. Results showed that waxy maize starch hydrolysis followed a two-stage kinetic profile with an initial stage characterized by high reaction rate, followed by a slower second stage. The change of hydrolysis rate occurred at approximately 6h of reaction, a time for which X-ray diffraction data quantitatively analyzed by three different techniques showed a maximum of crystallinity in partially hydrolyzed granules. Scanning electron microscopy images illustrated the action of α-amylases which implied the exoerosion of the granules surface, the entry of α-amylases into the granules through radial channels, their endoerosion towards the granule exterior, and their fragmentation. Fragmentation of waxy maize starch granules revealed internal layered structures of starch which were interpreted as hydrolyzed/non-hydrolyzed growth rings. Under the conditions chosen, kinetic, electron microscopy and X-ray data all gave evidence of a preferential action of α-amylase from Bacillus licheniformis towards the less ordered regions of waxy maize starch. Results showed that, provided the proper hydrolysis time is chosen, starch granules with increased crystallinity can be obtained by a pure enzymatic treatment.
蜡质玉米淀粉在缓冲介质中受到α-淀粉酶（地衣芽孢杆菌）的水解，以定量和部分水解淀粉颗粒的形态和结晶度两方面来确定反应的演变。收集到的数据允许研究这种α-淀粉酶对蜡质玉米淀粉颗粒的作用模式，特别关注淀粉无定形区域的优先水解。结果表明，蜡质玉米淀粉水解遵循两阶段动力学曲线，初始阶段反应速率高，随后是较慢的第二阶段。水解速率的变化发生在反应约 6 小时时，此时通过三种不同技术对 X 射线衍射数据进行定量分析显示，部分水解颗粒的结晶度达到最大值。扫描电子显微镜图像说明了α-淀粉酶的作用，这意味着颗粒表面的外侵蚀、α-淀粉酶通过径向通道进入颗粒、它们向颗粒外部的内切蚀以及它们的碎片化。蜡质玉米淀粉颗粒的碎片化揭示了淀粉的内部层状结构，这些结构被解释为已水解/未水解的生长环。在所选择的条件下，动力学、电子显微镜和 X 射线数据都证明了地衣芽孢杆菌的α-淀粉酶对蜡质玉米淀粉中较无序区域具有优先作用。结果表明，只要选择适当的水解时间，通过纯酶处理就可以获得结晶度增加的淀粉颗粒。
