Table_4_Extracellular Proteome Analysis and Flavor Formation During Soy Sauce Fermentation.XLSX

Aspergillus oryzae is an excellent strain for soy sauce fermentation because of its complicated enzyme system, especially protease. The aim of this study was to investigate the key enzymes and flavors during soy sauce fermentation, and a comparative assessment of extracellular enzymes during various fermentation stages at the proteomic level via iTRAQ analysis is presented. Many important enzymes related to the amino acid and glucose metabolisms participated in the material decomposition under high-salt stress. Dipeptidase, dipeptidyl aminopeptidase, leucine aminopeptidase, aspartic protease pep1, and extracellular metalloproteinase played positive roles during the early stage of soybean mash fermentation, whilst leucine aminopeptidase A and extracellular metalloproteinase NpI were the dominant proteolytic enzymes during the later period of fermentation. At the same time, β-glucosidase and β-xylanase exerted great effects upon glucose metabolism throughout the fermentation process. The results show that protease and amylolytic enzymes are complementary in the formation of flavors such as alcohols, acids, esters, aldehydes, furans, and pyrazines during soy sauce fermentation.

米曲霉（Aspergillus oryzae）因拥有复杂的酶系，尤以蛋白酶（protease）为著，是酱油发酵的优良菌株。本研究旨在探究酱油发酵过程中的关键酶类与风味物质，并通过iTRAQ分析，在蛋白质组学水平上对不同发酵阶段的胞外酶（extracellular enzymes）开展比较评价。诸多与氨基酸及葡萄糖代谢相关的重要酶类，参与了高盐胁迫下的物质降解过程。二肽酶（Dipeptidase）、二肽基肽酶（dipeptidyl aminopeptidase）、亮氨酸氨肽酶（leucine aminopeptidase）、天冬氨酸蛋白酶pep1（aspartic protease pep1）以及胞外金属蛋白酶（extracellular metalloproteinase）在豆醅发酵早期发挥正向调控作用；而亮氨酸氨肽酶A（leucine aminopeptidase A）与胞外金属蛋白酶NpI（extracellular metalloproteinase NpI）则为发酵后期的主要蛋白水解酶（proteolytic enzymes）。与此同时，β-葡萄糖苷酶（β-glucosidase）与β-木聚糖酶（β-xylanase）在整个发酵过程中对葡萄糖代谢均具有显著影响。研究结果表明，在酱油发酵过程中，蛋白酶与淀粉水解酶（amylolytic enzymes）在醇类、酸类、酯类、醛类、呋喃类及吡嗪类等风味物质的形成过程中具有协同互补效应。