Properties and applications of β‐glycosidase from Bacteroides thetaiotaomicron that specifically hydrolyses isoflavone glycosides

To modify the glycan part of glycosides, the gene encoding β‐glycosidase was cloned from Bacteroides thetaiotaomicron VPI‐5482. The cloned gene, bt_1780, was expressed in Escherichia coli MC1061 and the expressed enzyme was purified using Ni‐NTA affinity chromatography. The purified enzyme, BTBG, showed optimal activity at 50 °C and pH 5.5. Interestingly, this enzyme did not have any hydrolysing activity on ordinary β‐linkage–containing substrates such as xylobiose, lactose and cello‐oligosaccharide, but specifically hydrolysed isoflavone glycosides such as daidzin, genistin and glycitin. Compared to a commercial beta glucosidase, BTBG selectively hydrolysed isoflavone glycosides in soybean extract mixture solution. These results suggest that BTBG may be a specialized enzyme for the hydrolysis of glycosides and that the substrate specificity of BTBG is applicable for the bioconversion of isoflavone glycosides in the food industry.     

大豆中异黄酮类化学成分的研究

用w(C2H5OH)=70%的工业乙醇从脱脂大豆饼中提取大豆异黄酮,并依次用乙酸乙酯、正丁醇萃取,乙酸乙酯萃取部分经硅胶柱和SephadexLH-20柱层析,用V(CHCl3)∶V(CH3OH)=(12～4)∶1梯度洗脱。分离得到4种化合物,通过理化常数和光谱分析鉴定其化学结构,分别为大豆甙元(daidzein)、染料木素(genistein)、大豆甙(daidzin)、染料木甙(genistin)。     

纳豆制备过程中大豆异黄酮的转化条件

使用日本古法制备纳豆,从纳豆中分离筛选出高活性的纳豆菌为实验菌株。研究了纳豆制备过程中大豆异黄酮的转化情况,发酵液中的大豆异黄酮在大豆异黄酮糖苷酶的水解作用下水解掉侧链糖基,转化为活性更高的大豆异黄酮苷元。根据薄层层析法确定了大豆异黄酮转化为大豆异黄酮苷元的最佳培养条件:培养温度为37℃,培养时间2 d,pH 7.0,含水质量分数60%。发酵液中大部分的大豆异黄酮苷转化为大豆异黄酮苷元,从而得到更利于人体吸收的大豆异黄酮苷含量较高的纳豆制品。     

7-羟基-4’-甲基-异黄酮的合成

以对甲基苯乙酸、间苯二酚为原料,经合成脱氧安息香中间体,环合成7-羟基-4'-甲基-异黄酮.在脱氧安息香增碳环合的反应中,探索了3种不同的增碳环合试剂对反应的影响,较理想的环合试剂为BF3·Et2O-DMF-PCl5.该工艺路线条件温和,产率达到72%.     

大豆异黄酮的功能与应用

大豆异黄酮是大豆生长过程中形成的一类次生代谢产物。大量研究表明大豆异黄酮在防癌抗癌、防治心血管疾病、预防骨质疏松症等方面有重要作用、本文综述了大豆导黄酮的结构、组成、生理功能以及在国内外的应用。     

氧化石墨烯的制备及其催化水解大豆异黄酮

采用改良的Hummers法制备了负载有-SO3H、-COOH和-OH的氧化石墨烯,对其进行了结构表征。并首次以氧化石墨烯为催化剂,对天然产物大豆异黄酮糖苷水解反应进行了研究。实验结果显示氧化石墨烯在异黄酮糖苷水解反应中具有较好的催化活性,其最佳反应温度为105℃,此时3种大豆异黄酮糖苷的转化率分别达到94.3%,92.1%和88.8%,苷元的收率分别达到69.6%、60.6%和58.8%。其催化活性明显优于其他固体酸催化剂,如沸石HZSM-5和大孔树脂NKA-9,而与0.02 mol.L.1的硫酸相当。     

大豆功能性成分的开发现状

大豆是我国的一种传统食品,含有丰富的生理活性物质,包括有大豆蛋白质、大豆异黄酮、大豆皂苷、大豆低聚糖以及大豆膳食纤维等,此外大豆发酵制品还会产生一些生理活性成分如蛋白黑素、大豆多肽等。综述目前大豆功能性成分的开发现状,同时也介绍了它们所具有的相关生理功能。     

霉菌型豆豉和纳豆中异黄酮含量的比较研究

目的:比较纳豆和豆豉中异黄酮含量的组成变化。方法:利用超声波提取,采用高效液相色谱法测定,色谱柱填料为Hypersil ODS2(4.6 mm×250 mm,5μm),流动相为甲醇(A)-水(B)进行梯度洗脱,检测波长为255 nm。结果:豆豉与纳豆相比较,豆豉中大豆苷、黄豆黄苷、染料木苷、大豆甙元、黄豆黄素、染料木素的含量分别为11,未检出,25,320,65,380μg/g;纳豆中中大豆苷、黄豆黄苷、染料木苷、大豆甙元、黄豆黄素、染料木素的含量分别为330,73,410,12,3.3,28μg/g。结论:豆豉中甙元的含量高,纳豆中糖苷的含量高。     

大豆生理活性物质功能的研究进展

介绍了大豆异黄酮、大豆皂甙、大豆蛋白质及其多肽的营养和生理功能的研究进展,并讨论了这些生理活性物质在保健食品中的应用前景.     

Ripening temperature affects the content and distribution of isoflavones in sufu,a fermented soybean curd

Sufu, a fermented soybean curd, was prepared by ripening the salted tofu cubes in the Aspergillus oryzae‐fermented rice–soybean koji mash at 25, 35 or 45 °C for a period of 16 days. It showed that the 16‐day ripened sufu contains less total isoflavone content (629.29–739.68 μg g^?1 dried matter) than the salted tofu before ripening (942.59 μg g^?1 dried matter). Regardless of ripening temperature, ripening causes a major reduction in the content of β‐glucoside and malonylglucoside isoflavones along with a significant increase of aglycone isoflavone content. These changes were enhanced as the ripening period extended. Among the various treatments examined, sufu ripened at 45 °C showed the greatest increase in aglycone content coupled with the greatest decrease in malonylglucosides. The distribution of malonylglucosides decreased from an initial 40.32% in the tofu cube to 9.78% after 16 days of ripening at 45 °C. Meanwhile, the distribution of aglycone increased from 13.17% to 39.88%.