Energy Biosciences Institute, University of California, Berkeley, CA, USA.
Mol Syst Biol. 2013 Jun 18;9:674. doi: 10.1038/msb.2013.30.
The efficient production of biofuels from cellulosic feedstocks will require the efficient fermentation of the sugars in hydrolyzed plant material. Unfortunately, plant hydrolysates also contain many compounds that inhibit microbial growth and fermentation. We used DNA-barcoded mutant libraries to identify genes that are important for hydrolysate tolerance in both Zymomonas mobilis (44 genes) and Saccharomyces cerevisiae (99 genes). Overexpression of a Z. mobilis tolerance gene of unknown function (ZMO1875) improved its specific ethanol productivity 2.4-fold in the presence of miscanthus hydrolysate. However, a mixture of 37 hydrolysate-derived inhibitors was not sufficient to explain the fitness profile of plant hydrolysate. To deconstruct the fitness profile of hydrolysate, we profiled the 37 inhibitors against a library of Z. mobilis mutants and we modeled fitness in hydrolysate as a mixture of fitness in its components. By examining outliers in this model, we identified methylglyoxal as a previously unknown component of hydrolysate. Our work provides a general strategy to dissect how microbes respond to a complex chemical stress and should enable further engineering of hydrolysate tolerance.
从纤维素原料高效生产生物燃料需要高效发酵水解植物材料中的糖。然而，植物水解物还含有许多抑制微生物生长和发酵的化合物。我们使用 DNA 条形码突变体文库鉴定了在运动发酵单胞菌（44 个基因）和酿酒酵母（99 个基因）中对水解物耐受性很重要的基因。在柳枝稷水解物存在的情况下，过表达一个功能未知的 Z. mobilis 耐受性基因（ZMO1875）将其特定乙醇生产力提高了 2.4 倍。然而，37 种水解物衍生抑制剂的混合物不足以解释植物水解物的适应性特征。为了解构水解物的适应性特征，我们对 Z. mobilis 突变体文库中的 37 种抑制剂进行了分析，并将水解物中的适应性建模为其组成部分适应性的混合物。通过检查该模型中的离群值，我们鉴定出了甲基乙二醛是水解物中以前未知的成分。我们的工作提供了一种分析微生物如何应对复杂化学应激的一般策略，应该能够进一步提高水解物耐受性的工程设计。
