Mechanocatalytic partial depolymerization of lignocellulosic feedstock towards oligomeric glycans

Abstract

The depolymerization of lignocellulosic feedstock with a heterogeneous composition is a major challenge and usually leads to the formation of monosaccharides as the main products. Our work aims to convert such feedstocks into oligomeric glycans which are more valuable products compared to sugars, by using mechanocatalysis in a planetary ball mill as an effective conversion route. 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 of cellulose as a substrate resulted in a nearly fully 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.