Biosynthesis and conversion of phenolics and taste active compounds in food fermentations

食品发酵中酚类和呈味活性化合物的生物合成和转化

• 批准号: RGPIN-2019-04778
• 负责人: Gänzle, Michael
• 金额: $ 5.68万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=714887
• 关键词: Biosynthesis; conversion; phenolics; taste; active

Microbial metabolism determines and maintains the quality and safety of fermented foods. Lactobacilli are dominant representatives of fermentation microbiota in most fermented foods, including fermented cereal food. The applicant's research program generally aims to link the ecology and physiology of food-fermenting lactobacilli to their competitiveness in cereal fermentations and their impact on food quality. The long term aim of the proposed research programme is to characterize the metabolism of minor metabolites, particularly the formation of taste-active peptides and the conversion of phenolic compounds by lactobacilli, and to determine the impact of these metabolites on the sensory, nutritional, and textural quality of bread. Specifically, the proposed project aims to elucidate the genetic determinants of formation of -glutamyl peptides and conversion of phenolic acids, to understand the role of these metabolic pathways in the ecology of lactobacilli, and their contribution to improved bread quality. Taste active -glutamyl peptides impact the taste of foods by altering the perception of sweet, salty, and umami tasting compounds. This taste activity has been referred to as “kokumi” activity. -Glutamyl peptides accumulate to active concentrations in fermentation of soy sauce, long-ripened cheese, and in sourdough; however, their formation has typically been attributed to enzymes from the raw material rather than bacterial metabolism. Recent work of the applicant demonstrated that L. reuteri produces -glutamyl peptides in sourdough. Bioinformatic analyses identified -glutamate-cysteine ligases and glutaminases as enzymes that synthesise -glutamyl peptides. The contribution of -glutamyl peptides to the taste of bread will be determined by quantification of these peptides in sourdough and sourdough bread, and by sensory analysis of bread produced with wild type strains and mutant strains with deletions in glutaminases or -glutamate-cysteine synthase. Sensory analyses will particularly aim to employ strains of L. reuteri that accumulate -glutamyl peptides to produce salt-reduced bread without reduction of consumer preference. Phenolic acids that in cereals, vegetables, or fruits modulate the composition of fermentation microbiota through their antimicrobial activity; moreover, phenolic acids also are precursor compounds for flavour volatiles. The contribution of phenolic acid metabolism of lactobacilli to ecological fitness in cereal fermentations and the texture and sensory quality of fermented cereal foods is unknown. Work in the proposed project aims to identify putative enzymes with activity on phenolic acids by comparative genomics. Phenolic acid decarboxylases and reductases will be characterized after heterologous expression, and by characterization of isogenic deletion mutants, and their role for sourdough biochemistry and bread quality will be determined.

微生物代谢决定和维持发酵食品的质量和安全。在大多数发酵食品中，乳酸菌是发酵微生物群的主要代表，包括发酵谷物食品。申请者的研究计划一般旨在将食品发酵乳酸菌的生态学和生理学与它们在谷物发酵中的竞争力及其对食品质量的影响联系起来。拟议研究计划的长期目标是表征次要代谢物的新陈代谢，特别是风味活性多肽的形成和乳酸菌对酚类化合物的转化，并确定这些代谢物对面包的感官、营养和质构品质的影响。具体地说，这项拟议的项目旨在阐明谷氨酰肽的形成和酚酸转化的遗传决定因素，以了解这些代谢途径在乳酸菌生态中的作用，以及它们对改善面包品质的贡献。 味觉活性-谷氨酰肽通过改变人们对甜味、咸味和鲜味化合物的看法来影响食物的味道。这种品尝活动被称为“Kokumi”活动。-谷氨酰肽在酱油、长时间成熟的奶酪和酸面团的发酵中积累到活性浓度；然而，它们的形成通常归因于原材料中的酶而不是细菌的新陈代谢。申请人最近的工作证明，路氏乳杆菌在酸面团中产生-谷氨酰多肽。生物信息学分析确定谷氨酸-半胱氨酸连接酶和谷氨酰胺酶是合成谷氨酰多肽的酶。谷氨酰肽对面包味道的贡献将通过对酸面团和酸面团面包中这些肽的定量，以及通过对谷氨酰胺酶或谷氨酸半胱氨酸合成酶缺失的野生型菌株和突变菌株生产的面包的感官分析来确定。感官分析将特别针对利用积累谷氨酰肽的路氏杆菌菌株来生产低盐面包，而不会降低消费者的偏好。 谷物、蔬菜或水果中的酚酸，通过其抗菌活性调节发酵微生物群的组成；此外，酚酸也是风味挥发物的前体化合物。乳酸菌的酚酸代谢对谷物发酵的生态适宜性以及发酵谷物食品的质地和感官质量的贡献尚不清楚。拟议项目中的工作旨在通过比较基因组学确定对酚酸具有活性的推定酶。酚酸脱羧酶和还原酶将通过异源表达和等基因缺失突变体的鉴定来鉴定，并将确定它们对酸面团生化和面包品质的作用。