Why did we start Fermenting cereals? A molecular dissection of Ancient Bread and Beer making (FABB)

谷物作为人类饮食的一部分已有2万多年的历史，尽管啤酒和发酵面包等发酵谷物产品是最近的创新。虽然利用发酵来保存和提高食物的消化率和营养价值可能比新石器时代早几万年，但谷物发酵被认为是在6000到3500年前的古埃及建立的，在那里面包烘焙与啤酒酿造密切相关。人们对了解谷物发酵的早期创新非常感兴趣，这些创新为我们今天所知道的面包和啤酒奠定了基础。一个核心问题是用于发酵这些早期发酵面包和啤酒的微生物（酵母和细菌）的性质。虽然最早的啤酒和面包可能依赖于水果表面的野生酵母来添加风味，但另一种可能性是使用天然酵母培养物，这是一种野生酵母和乳酸菌（LAB）的稳定混合物，存在于谷物中。重要的是，酵母发酵在完全分解植酸盐方面比“纯”酵母发酵更有优势，植酸盐是谷物中存在的一种抗营养物质，会导致几种矿物质的缺乏。我们假设谷物发酵是在古埃及建立起来的，因为在谷物占饮食大部分的时候，它在谷物植酸盐的分解中提供了营养优势。在这个项目中，我们将使用古埃及面包和啤酒样本的古DNA （aDNA）测序和宏基因组分析，为古面包和啤酒的成分提供迄今为止最全面的分析。重要的是，我们将确定这些面包和啤酒中的酵母和实验室，并确定古埃及面包（和啤酒）是用酵母培养物制成的，还是只用酵母。我们还将使用最先进的生物分子分析来测量这些古代面包和啤酒样品中的植酸水平，以验证我们的假设，即发酵降低了植酸水平，增加了谷物食品的营养价值。我们将使用实验考古学来研究古埃及的烘焙过程，基于我们的宏基因组分析，最后，我们还将尝试从古埃及啤酒样本中分离出活酵母。

Cereals have formed part of the human diet for more than 20,000 years, though fermented cereal products such as beer and leavened bread are more recent innovations. Although the use of fermentation to preserve and to improve the digestibility and nutritional value of foods likely pre-dates the Neolithic by several tens of thousands of years, the fermentation of cereals is thought to have been established between 6,000 and 3,500 years ago in ancient Egypt, where bread baking was closely associated with beer brewing. There is considerable interest in understanding the early innovations in cereal fermentation that laid the foundations for the breads and beers we know today. A central question is the nature of the microorganisms (yeast and bacteria) used in the fermentation of these early leavened breads and beer. While the earliest beer and bread may have depended on wild yeasts present on the surface of fruits that were added to impart flavour, an alternative possibility is the use of spontaneous sourdough cultures, a stable mix of wild yeasts and lactic acid bacteria (LAB) present on cereal grain. Importantly, sourdough fermentation offers advantages over 'pure' yeast fermentation in the complete breakdown of phytate, an anti-nutrient present in cereal grains which contributes to several mineral deficiencies. We hypothesise that fermentation of cereals became established in ancient Egypt because it offered nutritional advantages in the breakdown of cereal phytate at a time when cereals made up the bulk of the diet. In this project we will use ancient DNA (aDNA) sequencing and metagenomic analysis of ancient Egyptian bread and beer samples, to provide the most comprehensive analysis to date of the ingredients of ancient bread and beer. Importantly, we will identify the yeast(s) and LABs in these breads and beers, and determine whether ancient Egyptian breads (and beer) were made with sourdough cultures, or with yeast only. We will also use state-of-the-art biomolecular analysis to measure phytate levels in these ancient bread and beer samples, to test our hypothesis that fermentation reduced phytate levels and increased the nutritional value of cereal foods. We will use experimental archaeology to investigate the ancient Egyptian baking process, based on our metagenomic analysis, and finally, we will also attempt to isolate live yeasts from ancient Egyptian beer samples.