走出青藏高原：拉格啤酒酵母的起源与演化

Out of the Tibetan Plateau: origin and evolution of lager yeast

摘要:

采用低温底层发酵的拉格(lager)啤酒15世纪开始在德国巴伐利亚地区出现，19世纪初流行至全世界，目前已成为全球产量最高的酒精饮料。目前已阐明，拉格啤酒发酵酵母为巴斯德酿酒酵母(Saccharomyces pastorianus)，该种是一个杂交种，由艾尔(ale)啤酒酵母(Saccharomyces cerevisiae)与野生真贝氏酿酒酵母(Saccharomyces eubayanus)杂交而成，后者赋予了拉格啤酒酵母的耐低温能力。近年的群体遗传学和群体基因组学研究表明，拉格啤酒酵母的野生亲本S. eubayanus起源于青藏高原，可能通过丝绸之路传播到了欧洲。比较基因组学研究表明，拉格啤酒酵母包含2个株系，即Ⅰ系/Saaz系和Ⅱ系/Frohberg系，早期分别流行于中欧和西欧地区。前者为近似异源3倍体，后者为近似异源4倍体。2个株系在耐低温、麦芽三糖利用和风味物质产生能力等方面具有明显差异。在中国普通微生物菌种保藏管理中心(China General Microbiological Culture Collection Center, CGMCC)保藏的S. pastorianus菌株绝大多数属于Ⅱ系/Frohberg系。野生S. eubayanus的发现为通过人工杂交创建新的啤酒酵母杂交菌株，从而为选育具有独特发酵性能的新型非转基因啤酒酵母菌株提供了新途径，可能会对啤酒酿造的未来产生重大影响。本文除简要介绍啤酒酵母的研究历史外，重点阐述近年来在拉格啤酒酵母的杂种特性、起源、演化和基因组构成等方面的最新研究进展，并指出需要进一步解决的问题和未来研究趋势。

Abstract:

Lager, produced from bottom-fermenting yeast (Saccharomyces pastorianus) at colder temperatures, was first created in Bavaria, Germany in the 15th century and spread all over the world in the early 19th century. It enjoys the highest production among the alcoholic beverages all over the world. S. pastorianus, a hybrid of ale yeast S. cerevisiae and the wild yeast S. eubayanus, features low-temperature tolerance which is inherited from S. eubayanus. Research in population genetics and genomics has shown that S. eubayanus originated from the Tibetan Plateau and migrated to Europe through the Silk Road. According to the studies in comparative genomics, two distinct genetic groups existed in S. pastorianus taxon: Group Ⅰ (Saaz) and Group Ⅱ (Frohberg) which were prevalent in central Europe and western Europe in the early period, respectively. The former is allotriploid (nearly 2n S. eubayanus+1n S. cerevisiae) and the latter is allotetraploid (nearly 2n S. eubayanus+2n S. cerevisiae). The two groups differ in low temperature tolerance, maltotriose utilization and flavor production abilities. Most of the S. pastorianus strains preserved in the China General Microbiological Culture Collection Center (CGMCC) belong to Group Ⅱ. The discovery of wild S. eubayanus strains provides a new avenue for the creation of new S. eubayanus×S. cerevisiae hybrids and thereby for breeding novel non-transgenic lager yeast strains with unique fermentation properties, which may have significant impact on the future beer brewing. This review briefly introduced the research history of lager yeast, particularly the recent research on the hybrid nature, origin, evolution, and genome characteristics of S. pastorianus, ending with a perspective on research trends in the future.