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

谷物已经成为人类饮食的一部分超过20，000年，尽管发酵谷物产品如啤酒和发酵面包是最近的创新。虽然发酵用于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数万年，但谷物发酵被认为是在6,000至3,500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。人们对理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的面包和啤酒奠定了基础。一个核心问题是用于这些早期发酵面包和啤酒发酵的微生物（酵母和细菌）的性质。虽然最早的啤酒和面包可能依赖于存在于水果表面的野生酵母来赋予风味，但另一种可能性是使用自发的酸面团培养物，野生酵母和存在于谷物上的乳酸菌（LAB）的稳定混合物。重要的是，酸面团发酵在植酸盐的完全分解方面优于“纯”酵母发酵，植酸盐是谷物中存在的一种抗营养素，会导致几种矿物质缺乏。我们假设谷物发酵在古埃及已经建立，因为它在谷物植酸盐分解中提供了营养优势，当时谷物占饮食的大部分。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，提供迄今为止最全面的古面包和啤酒成分分析。重要的是，我们将确定这些面包和啤酒中的酵母和LAB，并确定古埃及面包（和啤酒）是用酸面团培养物制成的，还是只用酵母制成的。我们还将使用最先进的生物分子分析来测量这些古老的面包和啤酒样品中的植酸盐水平，以验证我们的假设，即发酵降低了植酸盐水平，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品中分离活酵母。

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.