University of Alberta, Department of Agricultural, Food and Nutritional Science, Edmonton, Alberta, Canada.
University of Bonn, Department of Nutritional and Food Sciences, Molecular Food Technology, Bonn, Germany.
Food Microbiol. 2023 May;111:104206. doi: 10.1016/j.fm.2022.104206. Epub 2022 Dec 12.
The conversion of phenolic compounds by lactobacilli in food fermentations contributes to food quality. The metabolism of phenolics by lactobacilli has been elucidated in the past years but information on the contribution of specific enzymes in food fermentations remains scarce. This study aimed to address this gap by disruption of genes coding for the hydroxycimmanic acid reductase Par1, the hydroxycinnamic acid decarboxylase Pad, the hydrocinnamic esterase EstR, and strains with disruption of all three genes in Furfurilactobacillus milii FUA3583. The conversion of phenolics by Ff. milii and its isogenic mutants in sorghum fermentations was studied by LC-UV and LC-UV-MS/MS analyses. Ff. milii FUA3583 converted hydroxycinnamic acids predominantly with Par1. Vinylphenols were detected only in mutants lacking par1. A phenotype for the estR defective mutant was not identified. The formation of pyrano-3-deoxyanthocyanidins was observed only after fermentation with strains expressing Pad. Specifically, formation of these compounds was low with Ff. milii FUA3583, substantially increased in the Par1 mutant and abolished in all mutants with disrupted pad. Competition experiments with Ff. milii FUA3583 and its isogenic mutants demonstrated that expression of one of the two metabolic pathways for hydroxycinnamic acids increases the ecological fitness of the strain. Disruption of EstR in a Δpar1Δpar2Δpad background improved ecological fitness, indirectly demonstrating a phenotype of the esterase in Ff. milii. The documentation of the functionality of genes coding for conversion of hydroxycinnamic acids may support the selection of starter cultures for improved quality of fermented cereal products.
乳酸菌在食品发酵过程中对酚类化合物的转化有助于改善食品质量。近年来，人们已经阐明了乳酸菌对酚类化合物的代谢，但有关特定酶在食品发酵中的作用的信息仍然很少。本研究旨在通过敲除编码羟基肉桂酸还原酶 Par1、羟基肉桂酸脱羧酶 Pad 和氢肉桂酸酯酶 EstR 的基因以及敲除这三个基因的 Furfurilactobacillus milii FUA3583 菌株来填补这一空白。通过 LC-UV 和 LC-UV-MS/MS 分析研究了 F. milii 及其在高粱发酵中的同工酶突变体对酚类化合物的转化。F. milii FUA3583 主要通过 Par1 转化羟基肉桂酸。只有在缺乏 par1 的突变体中才检测到乙烯基酚。未鉴定出 estR 缺陷突变体的表型。只有在表达 Pad 的菌株发酵后才观察到吡喃-3-去氧花色苷的形成。具体而言，这些化合物的形成量在 F. milii FUA3583 中较低，在 Par1 突变体中显著增加，在所有敲除 pad 的突变体中则完全消除。用 F. milii FUA3583 和其同工酶突变体进行的竞争实验表明，两种羟基肉桂酸代谢途径之一的表达增加了菌株的生态适应性。在Δpar1Δpar2Δpad 背景下敲除 EstR 可提高生态适应性，间接地证明了酯酶在 F. milii 中的表型。编码转化羟基肉桂酸的基因的功能的证明可能支持选择用于改善发酵谷物产品质量的起始培养物。
