The role of oxygen in yeast metabolism during high cell density brewery fermentations
The role of oxygen in yeast metabolism during high cell density brewery fermentations
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DOI：
10.1007/s00253-009-1909-8
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发表时间：
2009-03
影响因子：
5
通讯作者：
P. Verbelen;Sofie Saerens;S. E. V. Mulders;F. Delvaux;F. Delvaux
中科院分区：
文献类型：
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作者：
P. Verbelen;Sofie Saerens;S. E. V. Mulders;F. Delvaux;F. Delvaux
啤酒发酵过程的体积生产率可以通过使用更高的发酵速率（即，较高的接种量）。然而，在这些高细胞密度发酵中观察到的降低的酵母净生长可对整个后续酵母世代的生理稳定性具有负面影响。研究了不同氧气条件（麦芽汁通气、麦芽汁充氧、酵母预充氧）的使用以提高高细胞密度发酵期间的生长产量，并系统地评估了酵母代谢和生理参数。随着更高程度的生长（取决于所施加的氧气条件），发酵能力和不饱和脂肪酸的形成也受到影响。与其他条件相比，麦汁充氧对酯的形成有显著的降低作用，这是由醇乙酰转移酶基因ATF1的表达降低引起的。在使用充氧麦芽汁的高细胞密度发酵和参考发酵的情况下，在发酵结束时观察到较低的糖原和海藻糖水平。BAP 2（编码支链氨基酸通透酶）、ERG 1（编码角鲨烯环氧酶）和应激反应基因HSP 12的表达水平主要受高细胞浓度的影响，而OLE1（编码脂肪酸去饱和酶）和氧化应激反应基因SOD 1和CTT 1的表达水平主要受细胞氧利用率的影响。这些结果表明，可以通过改善氧气条件来实现高细胞密度发酵的优化，而不会显著影响酵母的生理条件和啤酒质量。
The volumetric productivity of the beer fermentation process can be increased by using a higher pitching rate (i.e., higher inoculum size). However, the decreased yeast net growth observed in these high cell density fermentations can have a negative impact on the physiological stability throughout subsequent yeast generations. The use of different oxygen conditions (wort aeration, wort oxygenation, yeast preoxygenation) was investigated to improve the growth yield during high cell density fermentations and yeast metabolic and physiological parameters were assessed systematically. Together with a higher extent of growth (dependent on the applied oxygen conditions), the fermentation power and the formation of unsaturated fatty acids were also affected. Wort oxygenation had a significant decreasing effect on the formation of esters, which was caused by a decreased expression of the alcohol acetyl transferase geneATF1, compared with the other conditions. Lower glycogen and trehalose levels at the end of fermentation were observed in case of the high cell density fermentations with oxygenated wort and the reference fermentation. The expression levels ofBAP2(encoding the branched chain amino acid permease),ERG1(encoding squalene epoxidase), and the stress responsive geneHSP12were predominantly influenced by the high cell concentrations, whileOLE1(encoding the fatty acid desaturase) and the oxidative stress responsive genesSOD1andCTT1were mainly affected by the oxygen availability per cell. These results demonstrate that optimisation of high cell density fermentations could be achieved by improving the oxygen conditions, without drastically affecting the physiological condition of the yeast and beer quality.