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

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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.