PDF(Pubmed)
Abstract：
Beer brewing is a well-known process that still faces great challenges, such as the total consumption of sugars present in the fermentation media. Lager-style beer, a major worldwide beer type, is elaborated by Saccharomyces pastorianus (Sp) yeast, which must ferment high maltotriose content worts, but its consumption represents a notable problem, especially among Sp strains belonging to group I. Factors, such as fermentation conditions, presence of maltotriose transporters, transporter copy number variation, and genetic regulation variations contribute to this issue. We assess the factors affecting fermentation in two Sp yeast strains: SpIB1, with limited maltotriose uptake, and SpIB2, known for efficient maltotriose transport. Here, SpIB2 transported significantly more maltose (28%) and maltotriose (32%) compared with SpIB1. Furthermore, SpIB2 expressed all MAL transporters (ScMALx1, SeMALx1, ScAGT1, SeAGT1, MTT1, and MPHx) on the first day of fermentation, whereas SpIB1 only exhibited ScMalx1, ScAGT1, and MPH2/3 genes. Some SpIB2 transporters had polymorphic transmembrane domains (TMD) resembling MTT1, accompanied by higher expression of these transporters and its positive regulator genes, such as MAL63. These findings suggest that, in addition to the factors mentioned above, positive regulators of Mal transporters contribute significantly to phenotypic diversity in maltose and maltotriose consumption among the studied lager yeast strains.IMPORTANCEBeer, the third most popular beverage globally with a 90% market share in the alcoholic beverage industry, relies on Saccharomyces pastorianus (Sp) strains for lager beer production. These strains exhibit phenotypic diversity in maltotriose consumption, a crucial process for the acceptable organoleptic profile in lager beer. This diversity ranges from Sp group II strains with a notable maltotriose-consuming ability to Sp group I strains with limited capacity. Our study highlights that differential gene expression of maltose and maltotriose transporters and its upstream trans-elements, such as MAL gene-positive regulators, adds complexity to this variation. This insight can contribute to a more comprehensive analysis needed to the development of controlled and efficient biotechnological processes in the beer brewing industry.
摘要：
啤酒酿造是一个众所周知的过程，仍然面临巨大的挑战，例如发酵培养基中存在的糖的总消耗量。啤酒，全球主要的啤酒类型，由巴氏酵母菌(Sp)酵母精心制作，必须发酵高麦芽三糖含量的麦芽汁，但是它的消费代表了一个值得注意的问题，特别是在属于I组因子的Sp菌株中，如发酵条件，存在麦芽三糖转运蛋白，转运蛋白拷贝数变化，遗传调控变异导致了这个问题。我们评估了影响两种Sp酵母菌株发酵的因素：SpIB1，麦芽三糖吸收有限，和SpIB2，以高效的麦芽三糖运输而闻名。这里,与SpIB1相比,SpIB2运输显著更多的麦芽糖(28%)和麦芽三糖(32%)。此外，SpIB2在发酵的第一天表达所有MAL转运蛋白（ScMALx1，SeMALx1，ScAGT1，SeAGT1，MTT1和MPHx），而SpIB1仅显示ScMalx1、ScAGT1和MPH2/3基因。一些SpIB2转运蛋白具有类似于MTT1的多态性跨膜结构域（TMD），伴随着这些转运蛋白及其正调节基因的较高表达，例如MAL63。这些发现表明,除了上述因素之外，在研究的啤酒酵母菌株中，Mal转运蛋白的正调节剂显着促进了麦芽糖和麦芽三糖消耗的表型多样性。IMPORTANCEBeer,全球第三大最受欢迎的饮料，在酒精饮料行业占有90%的市场份额，依赖酿酒酵母（Sp）菌株生产啤酒。这些菌株在麦芽三糖消费中表现出表型多样性，啤酒中可接受的感官特征的关键过程。这种多样性的范围从具有显着的麦芽三糖消耗能力的SpII组菌株到具有有限能力的SpI组菌株。我们的研究强调了麦芽糖和麦芽三糖转运蛋白及其上游反式元件的差异基因表达，如MAL基因正调节因子，增加了这种变化的复杂性。这种见解可以有助于在啤酒酿造行业中开发受控和有效的生物技术过程所需的更全面的分析。
