The objective is to explore the effects of enhancing the activity of yeast ferulic acid decarboxylase (FDC1) on the level of 4-vinylguaiacol (4-VG) and the consumption of its precursor ferulic acid (FA) in top-fermented wheat beer. Expression of Bacillus pumilus FDC1 in brewer’s yeast showed a better effect on the FDC1 activity than overexpression of the endogenous enzyme. The 4-VG content was increased by 34%, and the consumption time of FA was shortened from 48 to 12 h. Since the intracellular accumulation of the FDC1 substrate did not increase over time, to reduce the FA transport burden on cells and shorten the decarboxylation time, B. pumilus FDC1 was further secreted extracellularly. The resulted strain showed a 65% increase in 4-VG content in the FA-containing medium, and produced about 3 mg L−1 4-VG in the top-fermented wheat beer, increasing by 61% than control. However, further increasing the secretory expression level of FDC1 only accelerated FA consumption. These results suggested that appropriate secretion of bacterial FDC1 into wort could be used as a potential alternative strategy to increase the level of 4-VG in top-fermented wheat beer.

中文翻译：

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啤酒酵母中短小芽孢杆菌阿魏酸脱羧酶的分泌表达提高上层发酵小麦啤酒中4-乙烯基愈创木酚的含量

目的是探讨提高酵母阿魏酸脱羧酶 (FDC1) 活性对上层发酵小麦啤酒中 4-乙烯基愈创木酚 (4-VG) 及其前体阿魏酸 (FA) 消耗的影响。啤酒酵母中短小芽孢杆菌 FDC1 的表达对 FDC1 活性的影响优于内源酶的过表达。4-VG含量增加34%，FA消耗时间由48小时缩短至12小时。由于 FDC1 底物的细胞内积累不会随时间增加，为了减少细胞的 FA 运输负担并缩短脱羧时间，短小芽孢杆菌 FDC1 进一步分泌到细胞外。所得菌株在含 FA 培养基中的 4-VG 含量增加了 65%，并在顶部发酵的小麦啤酒中产生了约 3 mg L-1 4-VG，比对照增加了 61%。然而，进一步增加 FDC1 的分泌表达水平只会加速 FA 的消耗。这些结果表明，将细菌 FDC1 适当分泌到麦芽汁中可作为一种潜在的替代策略，以增加顶部发酵小麦啤酒中 4-VG 的水平。