Department of Microbiology, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, 45320, Pakistan.
Mol Biol Rep. 2019 Aug;46(4):4565-4580. doi: 10.1007/s11033-019-04913-5. Epub 2019 Jun 26.
Polysaccharides including resistant starch are categorized as dietary fiber and are used as an important prebiotic. Similar to soluble fibers, resistant starch also has a number of physiological effects that have been shown to be beneficial for health. Starch hydrolyzing enzymes, most importantly amylases, play essential roles in the production of resistant starch. This study aimed to develop α-amylase-treated maize flour with slow digestibility and unique physicochemical characteristics compared to native maize flour. In the current study, resistant starch type III from maize flour was prepared using α-amylase obtained from indigenously isolated Bacillus licheniformis. The α-amylase gene from B. licheniformis was amplified and cloned into the pET-24(a) vector, expressed in E. coli BL21 (DE3) cells and purified by metal ion affinity chromatography. The purified enzyme enhanced the yield of resistant starch 16-fold in maize flour. Scanning electron microscopy revealed that the granular structure of maize flour was disrupted into a dense network with irregular structure, and X-ray diffractograms confirmed the transformation from an amorphous to a crystalline structure upon α-amylase treatment. Thermogravimetric analysis revealed increased amylose content of α-amylase-treated maize flour. Moreover, α-amylase-treated maize flour resulted in a significant enhancement of the desired properties of maize flour, such as resistant starch content, amylose, milk absorption capacity, and iodine and fatty acid complexing ability, and a reduction in swelling power, water binding, oil absorption capacity, and in vitro digestibility compared to untreated maize flour. Resistant starch type III showed low digestibility and increased complexing ability with iodine and fatty acid and therefore could be a safe and beneficial alternative as a coating material for the delivery of active, sensitive ingredients to the colon.
包括抗性淀粉在内的多糖被归类为膳食纤维，可用作重要的益生元。与可溶性纤维类似，抗性淀粉也具有多种生理作用，这些作用已被证明对健康有益。淀粉水解酶，尤其是淀粉酶，在抗性淀粉的生产中起着至关重要的作用。本研究旨在开发与天然玉米粉相比具有缓慢消化性和独特物理化学特性的α-淀粉酶处理玉米粉。在本研究中，使用从本地分离的地衣芽孢杆菌获得的α-淀粉酶来制备玉米粉中的 III 型抗性淀粉。从地衣芽孢杆菌中扩增和克隆α-淀粉酶基因，并将其表达在大肠杆菌 BL21（DE3）细胞中，然后通过金属离子亲和层析进行纯化。纯化后的酶可将玉米粉中抗性淀粉的产量提高 16 倍。扫描电子显微镜显示，玉米粉的颗粒结构被破坏成具有不规则结构的密集网络，X 射线衍射图证实了α-淀粉酶处理后从无定形到结晶结构的转变。热重分析表明α-淀粉酶处理的玉米粉中直链淀粉含量增加。此外，与未处理的玉米粉相比，α-淀粉酶处理的玉米粉可显著提高玉米粉的理想特性，如抗性淀粉含量、直链淀粉、牛奶吸收能力、碘和脂肪酸络合能力，同时降低膨胀力、水结合能力、吸油能力和体外消化率。III 型抗性淀粉消化率低，与碘和脂肪酸的络合能力增强，因此可以作为活性、敏感成分输送到结肠的涂层材料的安全、有益替代品。
