Centre for Malting and Brewing Science, Department of Microbial and Molecular Systems, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, 3001 Leuven, Heverlee, Belgium.
Appl Microbiol Biotechnol. 2010 Dec;88(6):1321-31. doi: 10.1007/s00253-010-2843-5. Epub 2010 Aug 31.
The brewer's yeast genome encodes a 'Flo' flocculin family responsible for flocculation. Controlled floc formation or flocculation at the end of fermentation is of great importance in the brewing industry since it is a cost-effective and environmental-friendly technique to separate yeast cells from the final beer. FLO genes have the notable capacity to evolve and diverge many times faster than other genes. In actual practice, this genetic variability may directly alter the flocculin structure, which in turn may affect the flocculation onset and/or strength in an uncontrolled manner. Here, 16 ale and lager yeast strains from different breweries, one laboratory Saccharomyces cerevisiae and one reference Saccharomyces pastorianus strain, with divergent flocculation strengths, were selected and screened for characteristic FLO gene sequences. Most of the strains could be distinguished by a typical pattern of these FLO gene markers. The FLO1 and FLO10 markers were only present in five out of the 18 yeast strains, while the FLO9 marker was ubiquitous in all the tested strains. Surprisingly, three strongly flocculating ale yeast strains in this screening also share a typical 'lager' yeast FLO gene marker. Further analysis revealed that a complete Lg-FLO1 allele was present in these ale yeasts. Taken together, this explicit genetic variation between flocculation genes hampers attempts to understand and control the flocculation behavior in industrial brewer's yeasts.
啤酒酵母基因组编码了一种“Flo”絮凝素家族，负责絮凝。在酿造工业中，控制发酵后期的絮凝形成或絮凝具有重要意义，因为这是一种经济高效且环保的从最终啤酒中分离酵母细胞的技术。FLO 基因具有显著的进化和分化能力，其速度比其他基因快得多。在实际应用中，这种遗传变异性可能会直接改变絮凝素的结构，从而可能以不可控的方式影响絮凝的起始和/或强度。在这里，选择了来自不同啤酒厂的 16 株艾尔和拉格酵母菌株、一株实验室酿酒酵母和一株参考的巴氏酵母菌株，它们具有不同的絮凝强度，并对其特征 FLO 基因序列进行了筛选。大多数菌株可以通过这些 FLO 基因标记的典型模式来区分。在 18 株酵母菌株中，只有 5 株存在 FLO1 和 FLO10 标记，而 FLO9 标记在所有测试菌株中普遍存在。令人惊讶的是，在这次筛选中，三种絮凝能力很强的艾尔酵母菌株也具有典型的“拉格”酵母 FLO 基因标记。进一步的分析表明，这些艾尔酵母中存在完整的 Lg-FLO1 等位基因。总之，这种絮凝基因之间的明显遗传变异阻碍了我们对工业酿造酵母絮凝行为的理解和控制。
