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首页> 外文期刊>Applied Microbiology >Quantitative Physiology of Non-Energy-Limited Retentostat Cultures of Saccharomyces cerevisiae at Near-Zero Specific Growth Rates
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Quantitative Physiology of Non-Energy-Limited Retentostat Cultures of Saccharomyces cerevisiae at Near-Zero Specific Growth Rates

机译：非能量限制的酿酒酵母在接近零比生长速率下的定量生理学

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So far, the physiology of Saccharomyces cerevisiae at near-zero growth rates has been studied in retentostat cultures with a growth-limiting supply of the carbon and energy source. Despite its relevance in nature and industry, the near-zero growth physiology of S. cerevisiae under conditions where growth is limited by the supply of non-energy substrates remains largely unexplored. This study analyzes the physiology of S. cerevisiae in aerobic chemostat and retentostat cultures grown under either ammonium or phosphate limitation. To compensate for loss of extracellular nitrogen- or phosphorus-containing compounds, establishing near-zero growth rates (μ ?1) in these retentostats required addition of low concentrations of ammonium or phosphate to reservoir media. In chemostats as well as in retentostats, strongly reduced cellular contents of the growth-limiting element (nitrogen or phosphorus) and high accumulation levels of storage carbohydrates were observed. Even at near-zero growth rates, culture viability in non-energy-limited retentostats remained above 80% and ATP synthesis was still sufficient to maintain an adequate energy status and keep cells in a metabolically active state. Compared to similar glucose-limited retentostat cultures, the nitrogen- and phosphate-limited cultures showed aerobic fermentation and a partial uncoupling of catabolism and anabolism. The possibility to achieve stable, near-zero growth cultures of S. cerevisiae under nitrogen or phosphorus limitation offers interesting prospects for high-yield production of bio-based chemicals.IMPORTANCE The yeast Saccharomyces cerevisiae is a commonly used microbial host for production of various biochemical compounds. From a physiological perspective, biosynthesis of these compounds competes with biomass formation in terms of carbon and/or energy equivalents. Fermentation processes functioning at extremely low or near-zero growth rates would prevent loss of feedstock to biomass production. Establishing S. cerevisiae cultures in which growth is restricted by the limited supply of a non-energy substrate therefore could have a wide range of industrial applications but remains largely unexplored. In this work we accomplished near-zero growth of S. cerevisiae through limited supply of a non-energy nutrient, namely, the nitrogen or phosphorus source, and carried out a quantitative physiological study of the cells under these conditions. The possibility to achieve near-zero-growth S. cerevisiae cultures through limited supply of a non-energy nutrient may offer interesting prospects to develop novel fermentation processes for high-yield production of bio-based chemicals.
机译：迄今为止，已经在具有限制生长的碳和能源供应的增稠剂培养物中研究了酿酒酵母在接近零生长速率下的生理学。尽管其在自然和工业上具有相关性，但在很大程度上由于没有能量底物的供应而限制了生长的条件下，酿酒酵母的生长生理几乎为零。这项研究分析了在有铵盐或磷酸盐限制的情况下生长的好氧化学恒温器和降压器培养物中酿酒酵母的生理。为了补偿细胞外含氮或磷的化合物的损失，要在这些稳压器中建立接近零的生长速率（μ？1），需要向储层介质中添加低浓度的铵或磷酸盐。在恒化器和阻滞剂中，观察到生长限制元素（氮或磷）的细胞含量大大降低，并且储存碳水化合物的积累水平很高。即使增长率接近于零，在非能量限制型稳压器中的培养力仍保持在80％以上，并且ATP合成仍然足以维持足够的能量状态并保持细胞处于代谢活跃状态。与类似的葡萄糖受限的稳压器培养物相比，氮和磷酸盐受限的培养物显示出需氧发酵以及分解代谢和合成代谢的部分解偶联。在氮或磷限制下实现酿酒酵母稳定，接近零生长的可能性为生物基化学品的高产量生产提供了有趣的前景。化合物。从生理学角度来看，这些化合物的生物合成在碳和/或能量当量方面与生物量形成竞争。发酵过程以极低或接近零的增长率运行，将防止原料损失到生物量生产中。因此，建立酿酒酵母培养物，其生长受到非能量底物供应有限的限制，因此可能具有广泛的工业应用前景，但在很大程度上尚未得到开发。在这项工作中，我们通过有限供应非能量营养素（即氮或磷源）实现了酿酒酵母的近乎零生长，并在这些条件下对细胞进行了定量生理研究。通过有限地供应非能量营养素来实现近零生长的酿酒酵母培养的可能性，可能为开发新颖的发酵工艺以高产量生产生物基化学品提供有趣的前景。

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