Molecular design of polysaccharides for improving the sustainable straw utilization value in rice

农作物秸秆可以被认为是一种丰富的农业废弃物。但是，农作物秸秆含有大量的细胞壁聚合物，也被称为木质纤维素，可以用作饲料，也可以作为可持续生产生物燃料等商品化学品的可再生资源。因此，将农作物秸秆转化为更高价值的产品对农业的可持续发展具有重要意义。将木质纤维作物原料加工成化学品包括原料的预处理和糖类的酶释放，然后由微生物发酵成产品。然而，并不是所有木质纤维素中的糖都能以同样的效率发酵。与戊糖相比，六糖更受发酵微生物的青睐。因此，增加木质纤维原料的含糖量，特别是己糖/戊糖的比例，将会增加产品的产量。在这两组研究的基础上，我们希望通过增加大米中的多糖、混合连接葡聚糖(MLG)和葡甘聚糖，同时减少木聚糖(富含戊糖的聚合物)来提高大米木质纤维材料中的糖和己糖/戊糖的比例。为了实现这些目标，我们计划：(I)确定和鉴定导致禾本科植物MLG含量高的植物候选基因；(Ii)揭示甘露聚糖酶如何控制甘露聚糖的合成；(Iii)通过基因组编辑CRISPR/Cas9方法将在(I)和(Ii)中获得的知识转移到水稻品种中，以增加水稻中这两种聚合物的丰度，而不会对植物生长和生物量生产产生负面影响。在水稻上的成功结果可以转移到更温和的牧草上，如大麦。因此，这一结果可能对中国和德国的可持续农业生产和农作物秸秆利用具有重要意义。

Crop straw can be considered an abundant agricultural waste. But, crop straw contains large amount of cell-wall polymers, also referred to as lignocellulosics, which can be used as feed and as a renewable resource for the sustainable production of commodity chemicals such as biofuels. Conversion of crop straw into higher value products is therefore of great importance for agriculture sustainability. Processing lignocellulosic crop materials to chemicals involves pretreatment of the material and enzymatic release of the sugars, which are then fermented to products by microbes. However, not all sugars present in lignocellulosics can be fermented with the same efficiency. Hexoses are preferred by fermenting microbes over pentoses. Hence, increasing the sugar content in particular the hexose/pentose ratio of lignocellulosic material will increase the product yield. Based on the previous studies of both groups we want to increase the sugar and hexose/pentose ratio in lignocellulosic material of rice by increasing the polysaccharides mixed-linkage glucan (MLG) and glucomannan in rice, while concomitantly reducing xylans (pentose rich polymers). To achieve these goals we plan to (i) identify and characterize plant candidate genes that contribute to high MLG content in grasses; (ii) uncovering how mannansynthases control (gluco)mannan synthesis; (iii) transferring the knowledge obtained in (i) and (ii) to rice varieties by the genome editing CRISPR/CAS9 approach to increase the abundance of both polymers in rice without negative impacts on plant growth and thus biomass production. A successful outcome in rice can be transferred to more temperate grasses such as barley. The outcome may therefore be of significant importance for China and Germany's sustainable agriculture production and crop straw utilization.