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KMID : 0545120100200040767
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Journal of Microbiology and Biotechnology
2010 Volume.20 No. 4 p.767 ~ p.774
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Construction of an industrial brewing yeast strain to manufacture beer with low caloric content and improved flavor
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Wang Jin-Jing
Wang Zhao-Yue
Liu Xi-Feng
Guo Xue-Na
He Xiu-Ping
Zhang Bo-Run
Wensel Pierre Christian
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Abstract
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In this study, the problems of high caloric content, increased maturation time and off-flavors in commercial beer manufacture arising from residual sugar, diacetyl, and acetaldehyde levels were addressed. A recombinant industrial brewing yeast strain (TQ1) was generated from T1 [Lipomyces starkeyi dextranase gene (LSD1) introduced, α-acetohydroxyacid synthase gene (ILV2) disrupted] by introducing Saccharomyces cerevisiae glucoamylase (SGA1) and a strong promoter PGK1 while disrupting the genes coding alcohol dehydrogenase (ADH2). The highest glucoamylase activity for TQ1 was 93.26 U/ml compared with host strain T1 (12.36 U/ml) and wild-type industrial yeast strain YSF5 (10.39 U/ml), respectively. European Brewery Convention (EBC) tube fermentation tests comparing the fermentation broths of TQ1 with T1 and YSF5 showed that the real extract were reduced by 15.79% and 22.47%; the main residual maltotriose concentration were reduced by 13.75% and 18.82%; the caloric content were reduced by 27.18 and 35.39 calories per 12 oz. Due to the disruption of ADH2 gene in TQ1, the off-flavor acetaldehyde concentration in the fermentation broth were 9.43% and 13.28% respectively lower than that of T1 and YSF5. No heterologous DNA sequences or drug-resistance genes were introduced into TQ1. So, the gene manipulations in this work properly solved the addressed problems in commercial beer manufacture.
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KEYWORD
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brewing, low-calorie, glucoamylase, dextranase, yeast
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