Lignocellulosic biomass is an abundant byproduct from cereal crops that can potentially be valorized as a feedstock to produce biomaterials. Zea mays CINNAMYL ALCOHOL DEHYDROGENASE 2 (ZmCAD2) is involved in lignification, and is a promising target to improve the cellulose‐to‐glucose conversion of maize stover. Here, we analyzed a field‐grown zmcad2 Mutator transposon insertional mutant. Zmcad2 mutant plants had an 18% lower Klason lignin content, whereas their cellulose content was similar to that of control lines. The lignin in zmcad2 mutants contained increased levels of hydroxycinnamaldehydes, i.e. the substrates of ZmCAD2, ferulic acid and tricin. Ferulates decorating hemicelluloses were not altered. Phenolic profiling further revealed that hydroxycinnamaldehydes are partly converted into (dihydro)ferulic acid and sinapic acid and their derivatives in zmcad2 mutants. Syringyl lactic acid hexoside, a metabolic sink in CAD‐deficient dicot trees, appeared not to be a sink in zmcad2 maize. The enzymatic cellulose‐to‐glucose conversion efficiency was determined after 10 different thermochemical pre‐treatments. Zmcad2 yielded significantly higher conversions compared with controls for almost every pre‐treatment. However, the relative increase in glucose yields after alkaline pre‐treatment was not higher than the relative increase when no pre‐treatment was applied, suggesting that the positive effect of the incorporation of hydroxycinnamaldehydes was leveled off by the negative effect of reduced p‐coumarate levels in the cell wall. Taken together, our results reveal how phenolic metabolism is affected in CAD‐deficient maize, and further support mutating CAD genes in cereal crops as a promising strategy to improve lignocellulosic biomass for sugar‐platform biorefineries.

中文翻译：

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玉米酚肉桂醇脱氢酶2（zmcad2）突变体的重排酚醛代谢和提高的糖化效率

木质纤维素生物质是谷类作物的丰富副产品，可以潜在地作为生产生物材料的原料加以增值。玉米（Zea mays）肉桂醇脱氢酶2（ZmCAD2）参与木质化，是提高玉米秸秆纤维素转化为葡萄糖的有前途的目标。在这里，我们分析了一个田间生长的zmcad2 Mutator转座子插入突变体。Z mcad2突变植物的Klason木质素含量低18％，而其纤维素含量与对照系相似。zmcad2中的木质素突变体含有升高水平的羟基肉桂醛，即ZmCAD2，阿魏酸和三辛酸的底物。阿魏酸修饰半纤维素没有改变。酚醛分析进一步揭示了羟基肉桂醛在zmcad2突变体中部分转化为（二氢）阿魏酸和芥子酸及其衍生物。丁香基乳酸己糖苷是缺乏CAD的双子叶植物中的代谢汇，似乎不是zmcad2玉米的汇。经过10种不同的热化学预处理后，确定了酶法纤维素到葡萄糖的转化效率。Zmcad2与对照组相比，几乎所有预处理均产生了显着更高的转化率。但是，碱预处理后葡萄糖产量的相对增加不高于不进行预处理时的相对增加，这表明羟基肉桂醛的掺入的积极作用被降低了对香豆醛的负面作用所抵消。细胞壁中的水平。综上所述，我们的结果揭示了缺CAD的玉米中酚类代谢如何受到影响，并进一步支持了谷物作物中CAD基因的突变，这是一种改善糖平台生物精炼厂木质纤维素生物量的有前途的策略。