Institute of Microbiology and Biotechnology, University of Bonn, Meckenheimer Allee 168, 53115, Bonn, Germany.
Appl Microbiol Biotechnol. 2021 Mar;105(6):2441-2453. doi: 10.1007/s00253-021-11168-3. Epub 2021 Feb 22.
There is an increasing public awareness about the danger of dietary sugars with respect to their caloric contribution to the diet and the rise of overweight throughout the world. Therefore, low-calorie sugar substitutes are of high interest to replace sugar in foods and beverages. A promising alternative to natural sugars and artificial sweeteners is the fructose derivative 5-keto-D-fructose (5-KF), which is produced by several Gluconobacter species. A prerequisite before 5-KF can be used as a sweetener is to test whether the compound is degradable by microorganisms and whether it is metabolized by the human microbiota. We identified different environmental bacteria (Tatumella morbirosei, Gluconobacter japonicus LMG 26773, Gluconobacter japonicus LMG 1281, and Clostridium pasteurianum) that were able to grow with 5-KF as a substrate. Furthermore, Gluconobacter oxydans 621H could use 5-KF as a carbon and energy source in the stationary growth phase. The enzymes involved in the utilization of 5-KF were heterologously overproduced in Escherichia coli, purified and characterized. The enzymes were referred to as 5-KF reductases and belong to three unrelated enzymatic classes with highly different amino acid sequences, activities, and structural properties. Furthermore, we could show that 15 members of the most common and abundant intestinal bacteria cannot degrade 5-KF, indicating that this sugar derivative is not a suitable growth substrate for prokaryotes in the human intestine. KEY POINTS: • Some environmental bacteria are able to use 5-KF as an energy and carbon source. • Four 5-KF reductases were identified, belonging to three different protein families. • Many gut bacteria cannot degrade 5-KF.
人们越来越意识到饮食中的糖会带来卡路里，并且在全球范围内导致超重现象的增加，因此，低卡路里的糖替代品对于替代食品和饮料中的糖具有很高的吸引力。果糖衍生物 5-酮-D-果糖（5-KF）是天然糖和人工甜味剂的有前途的替代品，它可以由多种葡糖醋杆菌属物种产生。在将 5-KF 用作甜味剂之前，需要先检验该化合物是否可被微生物降解，以及它是否可被人类微生物群代谢。我们鉴定了不同的环境细菌（游动放线菌、日本醋杆菌 LMG 26773、日本醋杆菌 LMG 1281 和巴氏梭菌），它们能够以 5-KF 为底物生长。此外，氧化葡萄糖酸杆菌 621H 可以在静止生长阶段将 5-KF 用作碳源和能源。参与 5-KF 利用的酶在大肠杆菌中异源过表达、纯化和表征。这些酶被称为 5-KF 还原酶，属于三个不相关的酶类，具有高度不同的氨基酸序列、活性和结构特性。此外，我们还表明，最常见和丰富的肠道细菌中的 15 个成员不能降解 5-KF，这表明这种糖衍生物不是人类肠道中细菌的合适生长底物。 关键点： • 一些环境细菌能够将 5-KF 用作能量和碳源。 • 鉴定出了四种 5-KF 还原酶，它们属于三种不同的蛋白质家族。 • 许多肠道细菌不能降解 5-KF。
