Bubble-induced transport is a ubiquitous natural and industrial phenomenon. In brewery, such transport occurs due to gas bubbles generated through anaerobic fermentation by yeasts. Two major kinds of fermentation viz. top (ale) and bottom (lager) fermentation, display a difference in their yeast distributions inside a sugar broth. The reason for this difference is believed to be yeast–bubble adhesion arising due to surface hydrophobicity of the yeast cell wall; however, the physical mechanism is still largely a mystery. In this report, through in vivo experiments, we develop a novel theoretical model for yeast distribution based on the general conservation law. This work clarifies that bubble-induced diffusion is the dominant transport mechanism in bottom-fermentation by lagers whereas, yeast–bubble adhesion plays a leading role in transporting ales in top-fermentation, thereby corroborating the centuries-old belief regarding distribution difference in yeast population in two kinds of fermentation.

中文翻译：

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发酵酵母的气泡诱导种群动态

气泡诱导运输是一种普遍存在的自然和工业现象。在啤酒厂中，这种运输是由于酵母厌氧发酵产生的气泡而发生的。两种主要的发酵即。顶部（麦芽酒）和底部（拉格）发酵，在糖汤中显示出它们酵母分布的差异。这种差异的原因被认为是由于酵母细胞壁的表面疏水性引起的酵母气泡粘附；然而，物理机制在很大程度上仍然是个谜。在本报告中，通过体内实验，我们基于一般守恒定律开发了一种新的酵母分布理论模型。这项工作阐明了气泡诱导扩散是拉格啤酒底部发酵的主要传输机制，而，