Saccharomyces cerevisiae exhibiting a modified route for uptake and catabolism of glycerol forms significant amounts of ethanol from this carbon source considered as 'non-fermentable'
Saccharomyces cerevisiae exhibiting a modified route for uptake and catabolism of glycerol forms significant amounts of ethanol from this carbon source considered as 'non-fermentable'
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麦角酵母菌通过改变甘油的吸收和分解途径，从这种被视为 "不可发酵 "的碳源中生成大量乙醇
DOI：
10.1186/s13068-019-1597-2
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发表时间：
2019-10-31
影响因子：
6.3
通讯作者：
Nevoigt, Elke
中科院分区：
文献类型：
--
作者：
Asskamp, Maximilian R.;Klein, Mathias;Nevoigt, Elke
背景由于甘油在生物柴油生产过程中不可避免的形成及其相对较高的还原度，甘油是微生物发酵过程中有吸引力的碳源。然而，甘油被真核平台生物酿酒酵母以完全呼吸方式分解代谢。我们以前设计了S。通过用NAD依赖性“DHA途径”替代天然FAD依赖性甘油分解代谢途径，酿酒酵母菌株有利于甘油的发酵代谢。此外，异源水甘油孔蛋白（Fps 1同系物）表达，以促进甘油的吸收。本研究旨在探讨S.酿酒厂的天然发酵产物乙醇由甘油引起的进行基因改造。这种理解应该有助于这种酵母的未来工程，用于将甘油发酵成比乙醇更有价值的产品。结果一株仅表现出甘油分解代谢途径替代的菌株产生接近检测限浓度的乙醇。异源aquaglyceroporin的表达引起显着的乙醇生产（8.5克L-1从51.5克L-1甘油消耗）在菌株中分解代谢甘油通过DHA途径，但不是在野生型背景。摇瓶培养物中氧可用性的减少进一步增加了乙醇滴度高达15.7 g L-1（从45 g L-1甘油消耗）。结论甘油分解代谢途径替代引起的胞浆NADH产量增加似乎是S.酿酒酵母在合成甘油培养基中生长。在具有异源水甘油孔蛋白的DHA途径菌株中，显著的代谢转换为乙醇形成，这支持了甘油更强流入伴随着经由DHA途径的细胞溶质NADH产生速率增加的假设。事实上，氧气供应的减少增加了DHA途径菌株中的乙醇产量，这与正常摇瓶培养物中的大部分甘油仍然以呼吸方式进入催化剂的假设一致。
Background Due to its inevitable formation during biodiesel production and its relatively high degree of reduction, glycerol is an attractive carbon source for microbial fermentation processes. However, glycerol is catabolized in a fully respiratory manner by the eukaryotic platform organism Saccharomyces cerevisiae. We previously engineered S. cerevisiae strains to favor fermentative metabolism of glycerol by replacing the native FAD-dependent glycerol catabolic pathway with the NAD-dependent 'DHA pathway'. In addition, a heterologous aquaglyceroporin (Fps1 homolog) was expressed to facilitate glycerol uptake. The current study was launched to scrutinize the formation of S. cerevisiae's natural fermentation product ethanol from glycerol caused by the conducted genetic modifications. This understanding is supposed to facilitate future engineering of this yeast for fermenting glycerol into valuable products more reduced than ethanol. Results A strain solely exhibiting the glycerol catabolic pathway replacement produced ethanol at concentrations close to the detection limit. The expression of the heterologous aquaglyceroporin caused significant ethanol production (8.5 g L-1 from 51.5 g L-1 glycerol consumed) in a strain catabolizing glycerol via the DHA pathway but not in the wild-type background. A reduction of oxygen availability in the shake flask cultures further increased the ethanol titer up to 15.7 g L-1 (from 45 g L-1 glycerol consumed). Conclusion The increased yield of cytosolic NADH caused by the glycerol catabolic pathway replacement seems to be a minimal requirement for the occurrence of alcoholic fermentation in S. cerevisiae growing in synthetic glycerol medium. The remarkable metabolic switch to ethanol formation in the DHA pathway strain with the heterologous aquaglyceroporin supports the assumption of a much stronger influx of glycerol accompanied by an increased rate of cytosolic NADH production via the DHA pathway. The fact that a reduction of oxygen supply increases ethanol production in DHA pathway strains is in line with the hypothesis that a major part of glycerol in normal shake flask cultures still enters the catabolism in a respiratory manner.