To enhance the competitiveness of industrial lignocellulose ethanol production, robust enzymes and cell factories are vital. Lignocellulose derived streams contain a cocktail of inhibitors that drain the cell of its redox power and ATP, leading to a decrease in overall ethanol productivity. Many studies have attempted to address this issue, and we have shown that increasing the glutathione (GSH) content in yeasts confers tolerance towards lignocellulose inhibitors, subsequently increasing the ethanol titres. However, GSH levels in yeast are limited by feedback inhibition of GSH biosynthesis. Multidomain and dual functional enzymes exist in several bacterial genera and they catalyse the GSH biosynthesis in a single step without the feedback inhibition. To test if even higher intracellular glutathione levels could be achieved and if this might lead to increased tolerance, we overexpressed the genes from two bacterial genera and assessed the recombinants in simultaneous saccharification and fermentation (SSF) with steam pretreated spruce hydrolysate containing 10% solids. Although overexpressing the heterologous genes led to a sixfold increase in maximum glutathione content (18 µmol g_drycellmass⁻¹) compared to the control strain, this only led to a threefold increase in final ethanol titres (8.5 g L^− 1). As our work does not conclusively indicate the cause-effect of increased GSH levels towards ethanol titres, we cautiously conclude that there is a limit to cellular fitness that could be accomplished via increased levels of glutathione.

为了增强木质纤维素工业乙醇生产的竞争力，强大的酶和细胞工厂至关重要。木质纤维素衍生的物流包含抑制剂混合物，这些抑制剂耗尽了细胞的氧化还原能力和ATP，导致整体乙醇生产率下降。许多研究试图解决这个问题，并且我们已经表明，增加酵母中的谷胱甘肽（GSH）含量可以赋予对木质纤维素抑制剂的耐受性，随后增加乙醇滴定度。但是，酵母中的GSH水平受到GSH生物合成反馈抑制的限制。多域和双重功能酶存在于多个细菌属中，它们在没有反馈抑制的情况下一步催化GSH生物合成。为了测试是否可以达到更高的细胞内谷胱甘肽水平，以及是否可能导致更高的耐受性，我们过分表达了两个细菌属的基因，并使用含10％固体的蒸汽预处理云杉水解产物同时糖化和发酵（SSF）评估了重组体。尽管过表达异源基因导致最大谷胱甘肽含量增加了六倍（18 µmol g与对照菌株相比，_{干细胞质量}^-1）仅导致最终乙醇滴定度（8.5 g L ^-1）增加了三倍。由于我们的工作并没有最终表明GSH水平升高对乙醇滴度的因果关系，因此我们谨慎地得出结论，通过增加谷胱甘肽水平可以实现细胞适应性的极限。