Preparation of high-quality resistant dextrin through pyrodextrin by a multienzyme complex

As a soluble food raw material with a low calorie content,resistant dextrin (RD) has broad application prospects in the food industry.Branching enzymes (BEs),as a key enzyme for RD preparation,can break the α-1,4 glycosidic bonds of donor chains and reconstruct the cleaved chains to acceptor chains through the α-1,6 glycosidic bonds.BEs with high transglucosidic activity toward amylopectin and short-chain substrates are urgently needed to increase the quality of RD.Herein,BE derived from Thermuobifida fusca (TfBE) was mined and characterized.The optimal temperature and pH of the TfBE were 40 ℃ and 6.5,respectively.A total of 1500 U/g substrate TfBE reacted with 20% (w/v) pyrodextrin for 12 h,the ratio of α-1,4 to α-1,6 glycosidic bonds was changed from 3.52:1 to 2.33:1,and the content of enzyme-resistant components notably increased from 44.0% to 53.8%.Furthermore,to make full use of receptor chains and small molecular sugars in the reaction system,a multienzyme complex of TfBE with T.fusca α-cyclodextrin glucosyltransferase (TfCGTase),TfBE with TfCGTase and Aspergillus nidulans α-glucosidase (AnGS) was used to further increase the enzyme resistance of RD from 44.0% to 65.3% and 70.6%,respectively.The developed multienzyme complex method could effectively contribute to improving the production quality and efficiency of RD preparation.

分支酶介入酸热法制备焦糊精的工艺优化

抗性糊精属于小分子、低热量的膳食纤维,被广泛应用于食品行业中,其中保健品应用市场最大,占比38.7%。但目前高温酸热生产抗性糊精普遍得率低、副产物多。研究以低水分玉米淀粉为原料利用高温酸热法制备焦糊精,通过单因素实验优化工艺,确定最佳工艺参数,细化操化手法,增加吸酸预反应过程,得率可达61.9%,在此基础上,引入淀粉分支酶作用焦糊精,催化α-1,4向α-1,6糖苷键转化,得率可达68.5%,葡萄糖聚合度有所增加,抗性含量提高1.2%。

Radioprotectors from pyrodextrins

Cornstarch heated in the range of 230-280°C depolymerized into pyrodextrins characterized by two-component EPR signals of relatively stable free radicals.These thermally generated radicals could serve as efficient scavengers for free radicals generated from pyrodextrins with the 200 Gy dose of γ-radiation.The most efficient traps/scavengers were produced from cornstarch at 250-280°C.IR data indicated incorporation of the OH groups to the pyrodextrins.These groups most probably originated from the OH· radicals formed by the radiolysis of water.EPR spectra provided evidence for trapping free radicals generated by γ-irradiation and for their subsequent annihilation on contact with pyrodextrins.Water affected radical processes occurring in pyrodextrins caused by γ-irradiation.

Thermus thermophilus分支酶的重组表达及其在抗性糊精制备中的应用

本文研究了来源于Thermus thermophilus的淀粉分支酶TtSBE,通过基因工程的方法构建重组大肠杆菌E.coli BL21(PET-24(a+)-TtSBE),使之在大肠杆菌内高效表达,并在此基础上对TtSBE的酶学性质进行研究,结果表明,TtSBE的最适pH为6.5,最适温度为60℃,在60℃的半衰期为40 h左右,TtSBE经纯化后,比活为773.27 U/mg;以2%的焦糊精为底物,利用TtSBE制备抗性糊精,当酶转化温度为60℃,pH为6.5,加酶量为3000 U/g(焦糊精),酶转化时间为12 h时,抗性成分含量达到50%,较焦糊精原料中的抗性成分含量提高了7%,本研究为抗性糊精的产率和质量的进一步提高奠定了基础。

酸热加工对焦糊精结构和理化性质的影响研究进展

抗性糊精是抗消化、低热量的膳食纤维,具有降低血糖血脂、改善肠胃功能、促进益生菌增殖等功效。焦糊精是制备抗性糊精中的关键中间产物,也是产生抗性的主要来源,制备焦糊精的过程会产生很多新的不被人体消化酶降解的糖苷键,从而赋予焦糊精和抗性糊精“抗消化性”。作者从焦糊精的制备、分子结构、理化特性、主要应用及未来发展趋势进行综述,以期能促进焦糊精行业的可持续健康发展。