Whistler Center for Carbohydrate Research and Department of Food Science, Purdue University, 745 Agriculture Mall Dr., West Lafayette, IN 47906, USA.
Nestlé Research Center, Department of Food Science and Technology, PO Box 44, Vers-chez-les-blanc, Lausanne 26, 1000 Switzerland.
Food Funct. 2021 Nov 1;12(21):10658-10666. doi: 10.1039/d1fo02146j.
Insoluble dietary fibers are typically known to be poorly fermented in the large intestine. However, their value may be high as evidence shows that important butyrogenic bacteria preferentially utilize insoluble substrates to support their energy needs. The objective of this study was to increase fermentability of an insoluble bran fiber (pearl millet) while keeping it mostly insoluble to promote bacteria in the community that rely on fermentable insoluble dietary fibers. Following pretests with different processing methods, a combination of microwave and enzymatic treatments were applied to isolated pearl millet fiber to increase its accessibility of gut bacteria. human fecal fermentation was conducted and analyses were made for short chain fatty acids and microbiota changes. Combined microwave and enzymatic processing increased the amount of insoluble fiber fermented from 36 to 59% of total dietary fiber, with a minor increase in soluble fiber (8%). Microwave/enzymatic processing doubled butyrate production and almost tripled acetate production at 6 h fermentation compared to the native millet fiber. 16S rRNA gene sequencing showed that the processing promoted a significant increase in Firmicutes/Bacteroidetes ratio compared to the native fiber with relative abundance increases in and genera and a decrease in Bacteroidetes. Overall, these data show that processing techniques can be used to increase the value of insoluble fiber, presumably by increasing accessibility of the fiber to degrading bacteria, and to support Firmicutes that preferentially compete on insoluble fibers.
不可溶性膳食纤维通常在大肠中发酵不良。然而，它们的价值可能很高，因为有证据表明，重要的产丁酸菌优先利用不可溶性底物来满足其能量需求。本研究的目的是提高不可溶性糠纤维（珍珠粟）的发酵性，同时保持其大部分不可溶性，以促进依赖可发酵不可溶性膳食纤维的菌群。在对不同加工方法进行预试验后，采用微波和酶处理相结合的方法对分离的珍珠粟纤维进行处理，以增加其对肠道细菌的可及性。进行了人粪便发酵，并对短链脂肪酸和微生物群变化进行了分析。微波/酶联合处理使不可溶性膳食纤维的发酵量从总膳食纤维的 36%增加到 59%，而可溶性膳食纤维（8%）略有增加。与天然小米纤维相比，微波/酶处理使丁酸的产量增加了一倍，乙酸的产量增加了近两倍，在 6 小时发酵时达到峰值。16S rRNA 基因测序显示，与天然纤维相比，该处理显著增加了厚壁菌门/拟杆菌门的比例，而 和 属的相对丰度增加，拟杆菌门的相对丰度降低。总的来说，这些数据表明，加工技术可以用来提高不可溶性纤维的价值，这可能是通过增加纤维对降解细菌的可及性，并支持优先利用不可溶性纤维的厚壁菌门来实现的。
