Industrial biotechnology will play an increasing role in creating a more sustainable global economy. For conventional aerobic bioprocesses supplying O2 can account for 15% of total production costs. Microbubbles (MBs) are micron-sized bubbles that are widely used in industry and medical imaging. Using a fluidic oscillator to generate energy-efficient MBs has the potential to decrease the costs associated with aeration. However, little is understood about the effect of MBs on microbial physiology. To address this gap, a laboratory-scale MB-based Saccharomyces cerevisiae Ethanol Red propagation–fermentation bioethanol process was developed and analysed. Aeration with MBs increased O2 transfer to the propagation cultures. Titres and yields of bioethanol in subsequent anaerobic fermentations were comparable for MB-propagated and conventional, regular bubble (RB)-propagated yeast. However, transcript profiling showed significant changes in gene expression in the MB-propagated yeast compared to those propagated using RB. These changes included up-regulation of genes required for ergosterol biosynthesis. Ergosterol contributes to ethanol tolerance, and so the performance of MB-propagated yeast in fed-batch fermentations sparged with 1% O2 as either RBs or MBs were tested. The MB-sparged yeast retained higher levels of ergosteryl esters during the fermentation phase, but this did not result in enhanced viability or ethanol production compared to ungassed or RB-sparged fermentations. The performance of yeast propagated using energy-efficient MB technology in bioethanol fermentations is comparable to that of those propagated conventionally. This should underpin the future development of MB-based commercial yeast propagation.

中文翻译：

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用于生物乙醇生产的微泡酵母繁殖发酵工艺。


工业生物技术将在创造更加可持续的全球经济方面发挥越来越重要的作用。对于传统的需氧生物过程，供应 O2 可占总生产成本的 15%。微泡（MB）是微米大小的气泡，广泛应用于工业和医学成像。使用射流振荡器产生节能的MB有可能降低与曝气相关的成本。然而，人们对 MB 对微生物生理学的影响知之甚少。为了解决这一差距，开发并分析了实验室规模的基于 MB 的酿酒酵母乙醇红繁殖-发酵生物乙醇工艺。 MB 通气增加了 O2 向繁殖培养物的转移。 MB 繁殖酵母和传统的常规气泡 (RB) 繁殖酵母在随后的厌氧发酵中的生物乙醇滴度和产量相当。然而，转录谱分析显示，与使用 RB 繁殖的酵母相比，MB 繁殖的酵母中基因表达发生显着变化。这些变化包括麦角甾醇生物合成所需基因的上调。麦角甾醇有助于乙醇耐受，因此在 RB 或 MB 时，测试了 MB 繁殖的酵母在用 1% O2 喷射的分批补料发酵中的性能。 MB喷射的酵母在发酵阶段保留了较高水平的麦角固醇酯，但这并没有导致与未通气或RB喷射的发酵相比活力或乙醇产量的增强。在生物乙醇发酵中使用节能 MB 技术繁殖的酵母的性能与传统繁殖的酵母的性能相当。这将为基于 MB 的商业酵母繁殖的未来发展奠定基础。