Biotechnology Letters, Vol.42, No.12, 2711-2720, 2020
Increasing the level of 4-vinylguaiacol in top-fermented wheat beer by secretory expression of ferulic acid decarboxylase fromBacillus pumilusin brewer's yeast
Objective 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. Results Expression ofBacillus pumilus FDC1in 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. pumilusFDC1 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. Conclusions 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.
Keywords:Bacillus pumilus;Ferulic acid;Ferulic acid decarboxylase;Top-fermented wheat beer;4-vinylguaiacol;Yeast