Studer, Michael Hans-PeterMichael Hans-PeterStuderDeMartini, J. D.J. D.DeMartiniDavis, M. F.M. F.DavisSykes, R. W.R. W.SykesDavison, B.B.DavisonKeller, M.M.KellerTuskan, G. A.G. A.TuskanWyman, C. E.C. E.Wyman2024-11-192024-11-192011-04-120027-842410.24451/arbor.10127https://doi.org/10.24451/arbor.1012710.1073/pnas.1009252108https://arbor.bfh.ch/handle/arbor/31538he primary obstacle to producing renewable fuels from lignocellulosic biomass is a plant's recalcitrance to releasing sugars bound in the cell wall. From a sample set of wood cores representing 1,100 individual undomesticated Populus trichocarpa trees, 47 extreme phenotypes were selected across measured lignin content and ratio of syringyl and guaiacyl units (S/G ratio). This subset was tested for total sugar release through enzymatic hydrolysis alone as well as through combined hot-water pretreatment and enzymatic hydrolysis using a high-throughput screening method. The total amount of glucan and xylan released varied widely among samples, with total sugar yields of up to 92% of the theoretical maximum. A strong negative correlation between sugar release and lignin content was only found for pretreated samples with an S/G ratio < 2.0. For higher S/G ratios, sugar release was generally higher, and the negative influence of lignin was less pronounced. When examined separately, only glucose release was correlated with lignin content and S/G ratio in this manner, whereas xylose release depended on the S/G ratio alone. For enzymatic hydrolysis without pretreatment, sugar release increased significantly with decreasing lignin content below 20%, irrespective of the S/G ratio. Furthermore, certain samples featuring average lignin content and S/G ratios exhibited exceptional sugar release. These facts suggest that factors beyond lignin and S/G ratio influence recalcitrance to sugar release and point to a critical need for deeper understanding of cell-wall structure before plants can be rationally engineered for reduced recalcitrance and efficient biofuels production.enQ1article