Mechanocatalytic partial depolymerization of lignocellulosic feedstock towards oligomeric glycans

The depolymerization of lignocellulosic feedstock with a heterogeneous composition is a major challenge and usually leads to the formation of monosaccharides as main products. Our work aims to convert such feedstock into oligomeric glycans as more valuable products compared to sugars, by using mechanocatalysis in a planetary ball mill in a cost-efficient and resource-saving manner. Herein, we utilized raw materials such as wheat straw, beet pulp, cocoa shells and apple pomace as residual natural raw materials from food and feed production. Reaction parameters such as rotational speed, acid content and milling duration were investigated and optimized towards a maximum amount of soluble species and a minimum of monosaccharides. The optimization for cellulose as substrate resulted in a nearly full-soluble fraction containing oligomeric glycans. Based on these results the reaction parameters were transferred and further optimized for lignocellulosic feedstock. For wheat straw a solubility of over 90 % was achieved comprising a mixture of oligomeric glycans as well as partially depolymerized lignin.